• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of mbcLink to Publisher's site
Mol Biol Cell. Sep 2007; 18(9): 3366–3374.
PMCID: PMC1951774

The Localization of Inner Centromeric Protein (INCENP) at the Cleavage Furrow Is Dependent on Kif12 and Involves Interactions of the N Terminus of INCENP with the Actin CytoskeletonAn external file that holds a picture, illustration, etc.
Object name is dbox.jpgAn external file that holds a picture, illustration, etc.
Object name is vbox.jpg

Ted Salmon, Monitoring Editor

Abstract

The inner centromeric protein (INCENP) and other chromosomal passenger proteins are known to localize on the cleavage furrow and to play a role in cytokinesis. However, it is not known how INCENP localizes on the furrow or whether this localization is separable from that at the midbody. Here, we show that the association of Dictyostelium INCENP (DdINCENP) with the cortex of the cleavage furrow involves interactions with the actin cytoskeleton and depends on the presence of the kinesin-6–related protein Kif12. We found that Kif12 is found on the central spindle and the cleavage furrow during cytokinesis. Kif12 is not required for the redistribution of DdINCENP from centromeres to the central spindle. However, in the absence of Kif12, DdINCENP fails to localize on the cleavage furrow. Domain analysis indicates that the N terminus of DdINCENP is necessary and sufficient for furrow localization and that it binds directly to the actin cytoskeleton. Our data suggest that INCENP moves from the central spindle to the furrow of a dividing cell by a Kif12-dependent pathway. Once INCENP reaches the equatorial cortex, it associates with the actin cytoskeleton where it then concentrates toward the end of cytokinesis.

INTRODUCTION

The chromosomal passenger proteins are an interesting group of proteins that play many important roles in cell division. The inner centromeric protein (INCENP), Aurora B, and Survivin associate with each other to form a chromosomal passenger-protein complex (CPC) known to exist in unicellular and multicellular organisms (Kang et al., 2001 blue right-pointing triangle; Bolton et al., 2002 blue right-pointing triangle; Cheeseman et al., 2002 blue right-pointing triangle). In addition, the chromosomal passenger proteins TD60 and Borealin can associate with the CPC and regulate its activity (Mollinari et al., 2003 blue right-pointing triangle; Gassmann et al., 2004 blue right-pointing triangle; Sampath et al., 2004 blue right-pointing triangle; Klein et al., 2006 blue right-pointing triangle). It has been well established that the CPC is essential for the regulation of chromosome condensation, chromosome congression, spindle formation, chromosome segregation, and cytokinesis (Mackay et al., 1998 blue right-pointing triangle; Kim et al., 1999 blue right-pointing triangle; Adams et al., 2001a blue right-pointing triangle; Giet and Glover, 2001 blue right-pointing triangle; Cheeseman et al., 2002 blue right-pointing triangle, 2004; Tanaka et al., 2002 blue right-pointing triangle; Sampath et al., 2004 blue right-pointing triangle).

A hallmark property of chromosomal passenger proteins is their dynamic localization during cell division. The CPC is localized on chromosomes and centromeres before metaphase and then is found on the spindle midzone during anaphase and at the cleavage furrow and midbody during cytokinesis (Cooke et al., 1987 blue right-pointing triangle; Earnshaw and Cooke, 1991 blue right-pointing triangle). The correct localization of the CPC at each stage of the cell cycle is crucial for its proper function. For example, an INCENP mutant that remains tethered to centromeres throughout mitosis inhibits cytokinesis (Eckley et al., 1997 blue right-pointing triangle). Interestingly, the chromosomal passenger proteins are interdependent on their localization (Adams et al., 2000 blue right-pointing triangle; Wheatley et al., 2001 blue right-pointing triangle; Honda et al., 2003 blue right-pointing triangle; Gassmann et al., 2004 blue right-pointing triangle). In particular, the kinase activity of Aurora B is important for the proper distribution of the CPC during cell division (Honda et al., 2003 blue right-pointing triangle). The dynamic localization of the CPC must be regulated by specific mechanisms acting at distinct locations of the cell at different stages of the cell cycle. Some of these mechanisms have been discovered in recent years. For example, the redistribution of the CPC from the centromeres to the spindle midzone is controlled by dephosphorylation of INCENP by the phosphatase CDC14 (Pereira and Schiebel, 2003 blue right-pointing triangle). In some systems, the mitotic kinesin-like protein (MKLP)-2 also seems to be essential for the redistribution of CPC from centromeres to the central spindle (Gruneberg et al., 2004 blue right-pointing triangle).

In contrast to these events in mitosis, the association of INCENP and other chromosomal passenger proteins with the cortex of the cleavage furrow has not been explored in detail. Immunofluorescence and electron microscopy studies have shown that INCENP associates with the cortex of the cleavage furrow during cytokinesis (Earnshaw and Cooke, 1991 blue right-pointing triangle; Eckley et al., 1997 blue right-pointing triangle). However, in most animal systems, it is difficult to distinguish the localization of the CPC at the spindle midzone from that at the cleavage furrow because they are often closely juxtaposed. The presence of the microtubule-rich midbody, derived from the spindle midzone makes this distinction even more difficult. In animal cells, all manipulations that abrogate localization of the CPC at the spindle midzone also result in lack of localization at the midbody (Ainsztein et al., 1998 blue right-pointing triangle; Mackay et al., 1998 blue right-pointing triangle; Honda et al., 2003 blue right-pointing triangle). By contrast, this distinction can be made more readily in Dictyostelium cells. The Dictyostelium spindle is slender compared with that of metazoans, and it is easily distinguished from the ingressing cleavage furrow. Furthermore, the Dictyostelium spindle is dismantled before the cleavage furrow severs the cell, and no midbody is formed (Roos and Camenzind, 1981 blue right-pointing triangle; Roos et al., 1984 blue right-pointing triangle; McIntosh et al., 1985 blue right-pointing triangle).

We showed previously that Dictyostelium INCENP (DdINCENP) localizes to the cortex of the cleavage furrow and that it is required for the abscission of the daughter cells (Chen et al., 2006 blue right-pointing triangle). Importantly, the distribution of DdINCENP at the cleavage furrow is altered by the loss of myosin II. Instead of the broad cleavage furrow distribution observed in wild-type cells, DdINCENP localizes as a narrow band at the equatorial plane of myosin II null cells. These observations suggested that DdINCENP may be able to interact with the actomyosin cytoskeleton (Chen et al., 2006 blue right-pointing triangle).

MKLPs, a subgroup of the kinesin-6 family of proteins, have been suggested to play an important role in regulating the localization of chromosomal passenger proteins during cell cycle (Gruneberg et al., 2004 blue right-pointing triangle). Dictyostelium has a single kinesin-6–related protein called Kif12. Kif12 localizes to the spindle midzone, and it is important for mitosis and cytokinesis (Lakshmikanth et al., 2004 blue right-pointing triangle). Normal localization of myosin II to the cleavage furrow requires Kif12, suggesting a possible interaction between Kif12 and the actomyosin cytoskeleton. Interestingly, Kif12 null mutants frequently fail in the abscission of daughter cells in a manner similar to DdINCENP null mutants (Lakshmikanth et al., 2004 blue right-pointing triangle). The similarity of localization and mutant phenotype of these two proteins prompted us to explore possible interactions between them. We show here that, in fact, Kif12 is required for the furrow localization of DdINCENP. We also determined that an amino-terminal portion of DdINCENP is required for furrow localization and that it is able interact with the actin cytoskeleton.

MATERIALS AND METHODS

Cell Culture, Transformation, and Constructs

The cells were cultured with HL-5 medium in Petri dishes at 19°C. Green fluorescent protein (GFP)-DdINCENP and GFP–Kif12 were described previously (Lakshmikanth et al., 2004 blue right-pointing triangle; Chen et al., 2006 blue right-pointing triangle). Both plasmids carry a Geneticin (G418)-resistance cassette. The constructs were introduced into cells with electroporation, and the transformants were selected in HL-5 medium with 10 μg/ml G418 (Invitrogen, Carlsbad, CA).

Microscopy of Live Cells

For live microscopy of mitotic cells, cells in log phase growth were plated on a small Petri dish with a coverslip on the bottom (MatTek, Ashland, MA). After the cells attached to the plate, the medium was removed, and it was replaced with low-fluorescence (LF) medium for at least 30 min before observations (Bretschneider et al., 2002 blue right-pointing triangle). The live imaging of the cells was conducted using a Nikon Eclipse TE200 microscope (Nikon Instruments, Dallas, TX) equipped with a 100× 1.4 numerical aperture PlanFluor Objective, shuttered illumination, and a Quantix 57 camera (Roper Scientific, Tucson, AZ) controlled by MetaMorph (Molecular Devices, Sunnyvale, CA). The exposure time for the GFP fluorescence was 50 ms with the interval time being at least 10 s.

Immunostaining and Microscopy of Fixed Cells

The cells were allowed to attach to acid-cleaned coverslips overnight in a 8.5-cm Petri dish, and then they were fixed according to published protocols (Koonce and McIntosh, 1990 blue right-pointing triangle). Briefly, the cells were fixed at room temperature with 2.5% formaldehyde in a 1,4-piperazinediethanesulfonic acid (PIPES)-EGTA buffer for 3 min followed by 1% formaldehyde in dehydrated methanol at −10°C for 5 min. The anti-α-tubulin antibody is a monoclonal antibody from Sigma-Aldrich (St. Louis, MO). The secondary antibody is a Texas Red-conjugated goat-anti-mouse antibody (Invitrogen). The protocol for 4,6-diamidino-2-phenylindole staining was described previously (Gerald et al., 2001 blue right-pointing triangle).

The protocol for staining F-actin was modified from the protocol described previously by Gerald et al. (1998) blue right-pointing triangle. Briefly, 2 × 105 cells were plated on a coverslip. Then, the cells were fixed with 3.7% formaldehyde in PDF (2 mM KCl, 1.1 mM K2HPO4, 1.32 mM KH2PO4, 0.1 mM CaCl2, and 0.25 mM MgSO4, pH 6.7) for 20 min at room temperature before being permeabilized by 0.2% Triton X-100 in phosphate-buffered saline (PBS) for 5 min. The coverslip was washed three times in a fixing chamber with PBS buffer before the cells were stained with Texas Red-conjugated phalloidin (Invitrogen) in PBS for 30 min in a covered humid chamber at room temperature. The coverslip was washed three times in PBS, and then it was rinsed briefly in distilled H2O before being mounted onto a glass slide.

Construction of Truncated DdINCENP Mutants

The C-terminal truncated mutants of DdINCENP were made by using internal restriction endonuclease sites in the DdINCENP gene. DdINCENP1-273 was made by cutting one of the internal EcoRI sites closest to the N terminus of the DdINCENP sequence. DdINCENP1-500 was made by cutting the only PvuII site in the gene. DdINCENP1-1013 was made by cutting the only BamHI site in the gene. In contrast, DdINCENP488-1321 was amplified with the primers AO386 (5′-GAGCTCGGTATTGCAA AGCCAACACCACTTAC-3′) and AO387 (5′-CTCGAGTTATTTTTTATTAACAATG ATTGGATTAGTAAAACCC-3′). All four truncated mutants were cloned downstream of the GFP sequence in the pTXGFP expression vector.

Tandem Affinity Purification (TAP) Purification

DdINCENP1-500 was cloned downstream of the TAP–GFP sequence in the pTX-TAPGFP plasmid constructed by Joe Mireles in our laboratory. The procedure for purifying the TAP-tagged protein in Dictyostelium was modified from the procedure described by Rigaut et al. (1999) blue right-pointing triangle and that by Koch et al. (2006) blue right-pointing triangle. For large-scale purification, 500 ml of cells expressing either TAP–GFP or TAP–GFP–DdINCENP1-500 were cultured in a 2-liter flask on a shaker at 200 rpm. The cells were harvested when the density reached 5 × 106 cells/ml and washed twice with PDF buffer. The cell pellet was resuspended in 40 ml of lysis buffer (50 mM Tris-Cl, 50 mM KCl, 2 mM MgCl2, 0.5 mM dithiothreitol [DTT], and 150 mM NaCl, pH 8.0) with protease inhibitors (5 μg/ml leupeptin, 0.1 mM phenylmethylsulfonyl fluoride, 1 mM tosyl-arginine-methylester 1 μg/ml trypsin inhibitor, 0.8 μM aprotinin, 1 mM benzamidine, 0.1 mM 4-(2-aminoethyl) benzenesulfonyl fluoride, 10 μM E-64, 1 μg/ml pepstatin, and 40 μM bebstatin) (Sigma-Aldrich). The suspension was passed three to four times through a nebulizer (BioNEB cell disrupter; Glas.Col, Terre Haute, IN) on ice. The cell lysate was centrifuged at 14,000 × g for 30 min. At the same time, 200 μl of immunoglobulin (Ig)G agarose beads (GE Healthcare, Little Chalfont, Buckinghamshire, United Kingdom) were preequilibrated and washed with 15 ml of IPP150 buffer (10 mM Tris-Cl, 150 mM NaCl, and 0.1% NP-40, pH 8.0). The IgG beads were added to the supernatant of the cell lysate and incubated on a rotator for 2 h at 4°C in a 50-ml tube to allow the TAP-tagged proteins to bind to the beads. The suspension was packed into a 15-ml column (Bio-Rad, Hercules, CA). The packed beads were washed with 30 ml of IPP150 buffer followed by 10 ml of TEV cleavage buffer (10 mM Tris-Cl, 150 mM NaCl, 0.1% NP-40, 0.5 mM EDTA, and 1 mM DTT, pH 8.0). Then, 150 U of AcTEV protease (Invitrogen) was added with 1 ml of TEV cleavage buffer to the column. The suspension was incubated at 4°C in the column on a rocker overnight to allow the thorough digestion of the proteins from the beads.

The flow-through (1 ml) from the column was collected, and a small aliquot was examined by SDS-polyacrylamide gel electrophoresis (PAGE) gel. As reported previously (Koch et al., 2006 blue right-pointing triangle), we found that this one step purification of our tagged proteins was sufficient to yield a highly pure preparation. Subsequent purification by binding to a calmodulin column (Rigaut et al., 1999 blue right-pointing triangle) did not improve the purity of our protein preparations.

Individual protein bands from the SDS-PAGE gel were excised and subjected to in-gel tryptic digestion (Shevchenko et al., 1996 blue right-pointing triangle). They were then identified through peptide mass fingerprinting (MASCOT; Matrix Sciences, Boston, MA). Tandem mass spectra were searched against the database of National Center for Biotechnology Information. Identification of the proteins was confirmed through manual evaluation of spectra. Mass spectrometry analysis was performed by the core facilities of the Institute for Cell and Molecular Biology at the University of Texas at Austin (Austin, TX).

RESULTS

The MKLP-related Protein Kif12 Localizes at the Cleavage Furrow and Is Required for the Localization of DdINCENP at the Cleavage Furrow

We showed previously that Kif12, like MKLP proteins in metazoans, is found on the Dictyostelium spindle during mitosis and that is important for mitosis and cytokinesis (Lakshmikanth et al., 2004 blue right-pointing triangle). Surprisingly, further detailed observations of cells expressing GFP–Kif12 revealed that a small but significant amount also localized at the ingressing cleavage furrow (Figure 1 and Supplemental Movie 1). Kif12 was never observed near the plasma membrane of interphase cells or in the polar cortical region of dividing cells, suggesting that its furrow localization may be tightly regulated and important for cytokinesis.

Figure 1.
Kif12 localizes on the spindle during mitosis and at the cleavage furrow during cytokinesis. Shown are two time-lapse fluorescence images of wild-type or Kif12 null cells expressing GFP–Kif12 during cytokinesis. GFP–Kif12 was found on ...

Because both Kif12 and DdINCENP are found at the central spindle and cleavage furrow (Supplemental Movies 1 and 2) and because the loss of either protein leads to a similar late cytokinesis defect (Lakshmikanth et al., 2004 blue right-pointing triangle; Chen et al., 2006 blue right-pointing triangle), we explored the possibility of an interaction between these two proteins during cytokinesis. We first determined whether Kif12 was required for the localization of DdINCENP during mitosis or cytokinesis by comparing the localization of GFP–DdINCENP in wild-type and Kif12 null cells. We found that GFP–DdINCENP localized normally to the spindle poles and central spindle during anaphase and telophase in both cells types. In contrast, GFP–DdINCENP did not localize at the cortex of the cleavage furrow in Kif12 null cells (Figure 2 and Supplemental Movie 3). The failure of DdINCENP to localize on the cleavage furrow was not due to a defective central spindle in these cells. We examined the morphology of the central spindle in Kif12 null cells, and we found that it was indistinguishable from that in wild-type cells (Supplemental Figure 1). In addition, we found that GFP–DdINCENP was retained on the central spindle of Kif12 null cells throughout cytokinesis. Even after the central spindle fractured into two halves, GFP–DdINCENP was still associated with the broken end of the dismantling spindle in each daughter cell (Figure 2 and Supplemental Movie 3). We observed a total of 14 Kif12 null cells undergoing mitosis and cytokinesis. Of these, five cells were able to initiate cytokinesis, and all of them failed to localize GFP–DdINCENP at the cortex of the cleavage furrow retaining it, instead, on their central spindle. The remaining nine cells were not able to initiate cytokinesis, although GFP–DdINCENP still localized on their central spindle (data not shown). We also examined the cleavage furrow of fixed Kif12 null cells, and we did not detect any GFP–DdINCENP at the cortex of the cleavage furrow (data not shown). Thus, these results suggest that Kif12 is required for the redistribution of DdINCENP from the central spindle to the cleavage furrow during cytokinesis.

Figure 2.
Kif12 is essential for the redistribution of DdINCENP from the central spindle to the cortex of the cleavage furrow. Fluorescence microscopy images of cells expressing GFP–DdINCENP during cytokinesis. (A and B) GFP–DdINCENP is normally ...

We then investigated the possibility that the localization of Kif12 and DdINCENP at the cleavage furrow is interdependent by determining the localization of GFP–Kif12 in DdINCENP null cells. We found that the localization of Kif12 did not change in the absence of DdINCENP. GFP–Kif12 still localized to the spindle midzone and cleavage furrow in DdINCENP null cells (Figure 3 and Supplemental Movie 4; n = 6). Therefore, Kif12 does not depend on DdINCENP to target to the region of the cleavage furrow.

Figure 3.
The localization of Kif12 during mitosis and cytokinesis does not depend on DdINCENP. Time-lapse fluorescence micrographs of DdINCENP null cells expressing GFP-DdKif12. (A) GFP-Kif12 still localized on the mitotic spindle (arrowheads) in an DdINCENP null ...

The N Terminus of DdINCENP Is Necessary for Cleavage Furrow Localization

Although the functions of INCENPs from different species are highly conserved, their sequences are not. Besides the small IN-box domain at their C termini and coiled-coil segments, no other sequence conservation is discernible among them (Adams et al., 2000 blue right-pointing triangle). Hence, it is not known what portion of INCENP proteins mediates their localization at the cleavage furrow. To address this question, we made a series of DdINCENP mutants tagged with GFP, and we expressed them in DdINCENP null cells.

The first truncation mutant lacking the N-terminal 487-amino acids DdINCENP488-1320 still contained the IN-box domain, a coiled-coil domain, and a nuclear localization signal (Figure 4). This protein was found in the nucleus of interphase cells (data not shown), and it was still able to localize on the mitotic spindle poles and central spindle (Figure 6). However, this mutant protein did not show any enrichment either at the cortex of the cleavage furrow or the cytoplasmic bridge connecting the two daughter cells (Figure 5 and Supplemental Movie 5).

Figure 4.
Domain analysis of DdINCENP. DdINCENP contains an IN-box domain near its C terminus, two coiled coil domains, and a single nuclear localization signal (*) at position 728–755. Shown are the four truncated mutants of DdINCENP used in this study. ...
Figure 5.
The N terminus of DdINCENP is essential for its localization at the cleavage furrow during cytokinesis. The four different truncated mutants of DdINCENP were tagged with GFP and expressed in DdINCENP null cells. Time-lapse fluorescence micrographs of ...
Figure 6.
Localization of DdINCENP at the central spindle does not depend on either the IN-box or its N-terminal domain. The GFP-tagged DdINCENP mutants were expressed in DdINCENP null cells. Fluorescence microscopy images of these cells during anaphase are shown. ...

In contrast, our second mutant, DdINCENP1-1013, which lacks the C-terminal IN-box domain, retained the ability to localize at the cleavage furrow of dividing cells (Figure 5 and Supplemental Movie 6). This protein also localized on the central spindle and poles (Figure 6). Thus, it seems that localization at the cleavage furrow is dependent on the amino-terminal portion of DdINCENP. Not surprisingly, neither of these two mutant proteins was able to rescue the cytokinesis defect of DdINCENP null cells (data not shown). Clearly, both localization at the furrow and the ability to interact with Aurora B kinase are important for its function during cytokinesis.

To further define the portion of DdINCENP involved in cleavage furrow localization, we constructed a mutant protein containing only the first 500 amino acids of DdINCENP. This protein lacks any nuclear localization signal, and it was thus found in the cytoplasm of interphase cells (see below). Interestingly, DdINCENP1-500 was able to enter the nucleus in mitosis and localized at the central spindle and spindle poles (Figure 6). Most importantly, DdINCENP1-500 was then able to localize at the cleavage furrow during cytokinesis and was clearly visible in the cytoplasmic bridge connecting the two daughter cells (Figure 5 and Supplemental Movie 7).

Because DdINCENP1-500 still contained one of the two coiled-coil portions found in DdINCENP, we decided to examine the requirement of this region for cleavage furrow localization of DdINCENP. We found that a smaller truncation protein, DdINCENP1-273, was still able to localize to the central spindle and the cleavage furrow during cytokinesis (Figures 5 and and66 and Supplemental Movie 8).

Logically, the requirement of Kif12 for the localization of DdINCENP at the cleavage furrow should also apply to these truncated mutants. Therefore, we investigated the localization of DdINCENP1-500 in the Kif12 null cells. Similar to full-length DdINCENP, DdINCENP1-500 failed to localize at the cleavage furrow in the absence of Kif12 (Supplemental Figure 2 and Supplemental Movies 9 and 10). This further confirmed our finding that Kif12 is required to target DdINCENP to the cortex of the cleavage furrow.

DdINCENP1-500 Interacts with the Actin Cytoskeleton

We showed previously that the distribution of DdINCENP at the cleavage furrow is modulated by myosin II, suggesting the ability of DdINCENP to interact with the actin–myosin cytoskeleton (Chen et al., 2006 blue right-pointing triangle). Presumably, this ability is found at the amino terminus of DdINCENP because this region was able to localize at the cleavage furrow (Figure 5). Thus, we decided to explore in more detail the behavior of this portion of DdINCENP.

Because DdINCENP1-500 lacks a nuclear localization signal (encoded by amino acids 728–755; Figure 4), it resided in the cytoplasm of interphase cells. We were intrigued to find that DdINCENP1-500 was associated with the cortex of the cell during interphase. In particular, we found that DdINCENP1-500 was prominently found at the base of pinocytic cups, actin-rich structures (Figure 7 and Supplemental Movies 11 and 12). Although we do not interpret this localization as a normal function of DdINCENP (full-length DdINCENP is never found on these structures), we see it as indicative of an intrinsic ability of the N terminus of DdINCENP to interact with the actin cytoskeleton. Indeed, we found that DdINCENP1-500 sedimented with the Triton X-100–insoluble cytoskeleton (data not shown). However, we should point out that we did not find DdINCENP1-500 in all actin-rich regions of the cell. For example, we did not see this protein at the leading pseudopod of migrating cells, which is enriched in many other F-actin–binding proteins (data not shown). Thus, we hypothesized that DdINCENP1-500 interacted with a particular portion of the actin cytoskeleton.

Figure 7.
DdINCENP1-500 associates with the actin cytoskeleton during interphase. (A) Time-lapse fluorescence micrographs of wild-type cells (WT) expressing GFP–DdINCENP1-500 are shown. The protein was enriched at the bottom portion of pinocytic cups (arrows) ...

To explore the interaction of DdINCENP1-500 with the actin cytoskeleton in more detail, we constructed a TAP-tagged GFP–DdINCENP1-500, which had a similar localization as the untagged protein (data now shown). The tagged protein was purified from Dictyostelium extracts. As a control we also purified proteins associated with TAP–GFP. By comparing the profiles of these two purifications, we identified four proteins that copurified with TAP–DdINCENP1-500 but not with TAP–GFP control (Figure 8). Mass spectrometry analysis revealed the identity of these proteins as myosin II, actin, heat-shock complex (HSC)70, and the actin-binding protein ABP-50. Western blot analysis of our fractions with an antibody against Kif12 failed to detect any Kif12 copurifying with GFP–DdINCENP1-500. However, because our purifications are prepared from asynchronous cultures, it is unlikely that we would copurify proteins that interact with GFP–DdINCENP1-500 during cytokinesis. Unfortunately, there are no currently available methods to synchronize Dictyostelium cultures to a satisfactory degree for these studies. Nonetheless, these results highlight the fact that the N terminus of DdINCENP has the ability to interact with a unique subset of the actin cytoskeleton.

Figure 8.
TAP-tagged GFP–DdINCENP1-500 associates with components of the actin cytoskeleton. TAP–GFP–DdINCENP1-500 and TAP–GFP were expressed separately in wild-type cells and purified by binding to IgG beads followed by cleavage ...

DISCUSSION

Kif12 Is Required for the Localization of DdINCENP at the Cleavage Furrow

The CPC has a dynamic localization during mitosis and cytokinesis. First, it localizes on the chromosome arms concentrating on centromeres at the transition from prophase to prometaphase. Then, it relocates to the central spindle at the transition from metaphase to anaphase. Finally, it redistributes to the cortex of the cleavage furrow as cells enter cytokinesis (Cooke et al., 1987 blue right-pointing triangle; Honda et al., 2003 blue right-pointing triangle). Some details about the molecular mechanisms controlling CPC movement have been recently described. In Saccharomyces cerevisiae, the action of CDC14 phosphatase regulates the localization of INCENP and Aurora B kinase at the central spindle (Pereira and Schiebel, 2003 blue right-pointing triangle). More recently, it has been demonstrated that MKLP2 is required for the redistribution of Aurora B kinase from centromeres to the central spindle (Gruneberg et al., 2004 blue right-pointing triangle). However, little is know about how the CPC can change localization from the central spindle to the cortex of the cleavage furrow at the beginning of cytokinesis.

Kif12 belongs to the KIF-6 family of kinesin-related proteins (Kollmar and Glockner, 2003 blue right-pointing triangle; Lakshmikanth et al., 2004 blue right-pointing triangle). It is the only member of this kinesin family in Dictyostelium, whereas there are three KIF-6 kinesins in human, including MKLP1, MKLP-2, and M phase phosphoprotein 1 (Miki et al., 2001 blue right-pointing triangle; Kollmar and Glockner, 2003 blue right-pointing triangle). All three mammalian MKLPs play important roles during cytokinesis (Hill et al., 2000 blue right-pointing triangle; Kuriyama et al., 2002 blue right-pointing triangle; Abaza et al., 2003 blue right-pointing triangle). Among the three, MKLP1 and MKLP2 have been well studied. Both of them localize to the central spindle at anaphase, and they highly concentrate in the midbody during cytokinesis. Additionally, they both can cross-link the antiparallel microtubules to help assemble the central spindle (Nislow et al., 1992 blue right-pointing triangle; Matuliene and Kuriyama, 2002 blue right-pointing triangle; Neef et al., 2003 blue right-pointing triangle). However, they play different roles during cytokinesis. MKLP-1 interacts with MgcRacGAP to form a centralspindlin complex, which interacts with RhoA (Mishima et al., 2002 blue right-pointing triangle, 2004 blue right-pointing triangle). In comparison, MKLP-2, also known as Rab6 kinesin (Echard et al., 1998 blue right-pointing triangle), is required for the redistribution of both Aurora B and Polo kinase from the centromeres to the central spindle (Neef et al., 2003 blue right-pointing triangle; Gruneberg et al., 2004 blue right-pointing triangle). ZEN-4 is the only kinesin-6 family protein found in Caenorhabditis elegans, and there are two kinesin-6 family proteins found in Drosophila, Pavarotti and KLP67A (Kollmar and Glockner, 2003 blue right-pointing triangle). Whereas loss of Pavarotti led to a complete failure of cleavage furrow ingression, loss of Zen-4 led to a late cytokinesis defect where the cleavage furrow would initiate but eventually regressed (Adams et al., 1998 blue right-pointing triangle; Raich et al., 1998 blue right-pointing triangle; Dean et al., 2005 blue right-pointing triangle). We have shown that Kif12 null cells have similar cytokinesis defects; some cells fail to initiate cleavage furrow formation (Lakshmikanth et al., 2004 blue right-pointing triangle), whereas others initiate but fail to complete cytokinesis.

We demonstrated here that Kif12 associates with the cleavage furrow in addition to its association with the mitotic spindle. This is similar to MKLP2, a Kif12 homologue known to be localized on the cleavage furrow during cytokinesis (Hill et al., 2000 blue right-pointing triangle). Interestingly, MKLP2 was initially identified as a Rab-6 binding protein (Echard et al., 1998 blue right-pointing triangle). Our data suggested that MKLP proteins may have an interaction with membranes of the cleavage furrow during cytokinesis. How this interaction occurs is not currently known.

We showed that Kif12, unlike its mammalian homologue, is not required for either spindle assembly or the localization of DdINCENP at the central spindle. However, we found that Kif12 is necessary for the redistribution of DdINCENP from the central spindle to the cortex of the cleavage furrow. This conclusion is consistent with the observation that Kif12 null cells have a late cytokinesis defect, which is similar to the defect found in DdINCENP null cells. These observations raised the possibility that Kif12 may be involved in directly transporting DdINCENP to the furrow. Alternatively, Kif12 may also transport a third protein to the central spindle, which in turn is required for DdINCENP to localize at the furrow. Myosin II is a protein known to require Kif12 to assemble at the cleavage furrow (Lakshmikanth et al., 2004 blue right-pointing triangle). Because we have shown here that DdINCENP interacts with the actin/myosin II cytoskeleton, it may seem plausible to postulate that Kif12 recruits myosin II, which in turn recruits DdINCENP to the cleavage furrow. However, we have shown previously that DdINCENP does not depend on myosin II to localize at the cleavage furrow (Chen et al., 2006 blue right-pointing triangle). Thus, we suggest that Kif12 is responsible for the localization of both DdINCENP and myosin II to the cleavage furrow.

We showed previously that DdINCENP localizes on equatorial furrows but not on ectopic (Rappaport) furrows (Chen et al., 2006 blue right-pointing triangle). Those observations suggested that DdINCENP may transfer directly from the central spindle to the cleavage furrow, because this will occur only at the equatorial plane. We would thus argue that the transport of DdINCENP to the cleavage furrow does not occur by astral microtubules, because such a mechanism would not distinguish between equatorial versus ectopic furrows. These conclusions would seem to be at odds with observations in mammalian cells showing INCENP on ectopic furrows (Savoian et al., 1999 blue right-pointing triangle). However, we would like to point out that in that paper cells also exhibited ectopic furrows that did not contain any INCENP, even though those furrows contained abundant microtubules. Only those ectopic furrows where the microtubules were organized into a midbody-like structure also contained INCENP. We reinterpret those data as suggesting that, like in Dictyostelium, metazoan INCENP also transfers equatorially from the central spindle to the cleavage furrow. A subsequent recruitment of INCENP to the metazoan midbody obscures this initial transfer to the furrow.

The IN-Box Domain Is Not Required for the Localization of DdINCENP at the Central Spindle and at the Cleavage Furrow

INCENP interacts with Aurora B with its C-terminal IN-box domain to act as both a substrate and regulator of Aurora B kinase (Adams et al., 2000 blue right-pointing triangle; Kaitna et al., 2000 blue right-pointing triangle; Kang et al., 2001 blue right-pointing triangle; Bishop and Schumacher, 2002 blue right-pointing triangle). Additionally, in some metazoans these proteins are interdependent for their localization during mitosis (Adams et al., 2001b blue right-pointing triangle; Honda et al., 2003 blue right-pointing triangle; Romano et al., 2003 blue right-pointing triangle). However, our data suggest that an interaction with Aurora B kinase may not be necessary for DdINCENP to localize at the central spindle and the cleavage furrow. All DdINCENP constructs lacking the IN-box domain, including the smallest, DdINCENP1-273, were found at the central spindle and the cleavage furrow. These results differ from those observed in mammalian cells where the N-terminal 405 amino acids of INCENP were able to localize on centromeres but failed to relocate to the central spindle during anaphase (Mackay et al., 1998 blue right-pointing triangle). However, it is important to note that the experiments in mammalian cells were carried out in the presence of endogenous INCENP, whereas we have expressed our constructs in INCENP null cells. Nonetheless, the interaction with Aurora kinase via the IN-box domain is clearly essential for function, because the expression of DdINCENP without this domain failed to rescue the cytokinesis defect of DdINCENP null cells.

The first 58 amino acids of mammalian INCENP can interact with Borealin and Survivin and localize to centromeres but not to the central spindle or cleavage furrow (Klein et al., 2006 blue right-pointing triangle). This portion of INCENP is not conserved between mammalian and S. cerevisiae INCENP proteins, even though both proteins bind to Survivin proteins. This suggests that a three-dimensional motif, not recognized in the primary sequence, is involved in the interaction between INCENP and Survivin. Because there are no discernible orthologues of Borealin or Survivin in the Dictyostelium genome, we surmise that the localization of DdINCENP may be regulated by a different mechanism.

DdINCENP Can Interact with the Actin Cytoskeleton by Its N-Terminal Region

The mechanism of INCENP localization at the cleavage furrow has not been explored in any detail. No previous study has determined whether INCENP is bound to the actin cytoskeleton or to the membrane of the furrow. We showed previously that the proper organization of DdINCENP at the cleavage furrow is dependent on myosin II suggesting the possibility of a direct interaction between DdINCENP and the actin–myosin cytoskeleton (Chen et al., 2006 blue right-pointing triangle). We have shown here that the N-terminal portion of DdINCENP is capable of interacting directly with the actin cytoskeleton. We found that the N-terminal domain of DdINCENP is able to localize to the cleavage furrow in a manner similar to the full-length protein. Interestingly, this portion of DdINCENP was also shown to interact with the actin cytoskeleton during interphase. DdINCENP1-500 was visible on the cortex of interphase cells and concentrated particularly on pinocytic cups. Macropinocytosis is an actin-dependent process that allows Dictyostelium cells to engulf the nutrient medium by forming a pinocytic cup. This process is known to involve many actin-associated proteins such as coronin, talin, and profilin (Cardelli, 2001 blue right-pointing triangle). Some of those proteins, which localize to the pinocytic sites, are also found at the cleavage furrow and have important functions during both pinocytosis and cytokinesis (Konzok et al., 1999 blue right-pointing triangle; Cardelli, 2001 blue right-pointing triangle; Rivero et al., 2002 blue right-pointing triangle).

Although the localization at the pinocytic cup is clearly not a native function of full-length DdINCENP, it does demonstrate the ability of this protein to interact with the actin cytoskeleton. The localization of DdINCENP1-500 at unique actin-rich structures, such as the pinocytic cup, also suggests that this fragment is not binding to the actin cytoskeleton in general, but to a specific subset of the actin cytoskeleton. Indeed, purification of DdINCENP1-500 identified a subset of actin cytoskeletal proteins that copurified with DdINCENP1-500, including ABP-50, Hsc70, actin, and myosin II. The actin binding protein ABP-50 has been shown to cross-link actin filaments during chemotaxis and to localize to actin rich extensions (Demma et al., 1990 blue right-pointing triangle; Dharmawardhane et al., 1991 blue right-pointing triangle). Hsc70 is known as a regulator of the actin capping proteins CAP32/34 (Haus et al., 1993 blue right-pointing triangle). Neither ABP-50 nor Hsc70 is known to concentrate on the cleavage furrow. Notably absent from our DdINCENP1-500 purification were the abundant actin cytoskeletal proteins ABP120, cortexillin, and α-actinin. Thus, we would suggest that DdINCENP has the intrinsic ability to bind directly to a specific network of actin cytoskeleton found at the cleavage furrow and that this ability is regulated in the context of the full-length protein, to occur only during cytokinesis. The DdINCENP1-500 fragment behaves as an un-regulated protein that still binds to the actin network at the cleavage furrow, but in addition, to the pinocytic cup. We hope that this protein can be used as a probe to define the structural elements at the cleavage furrow that are able to recruit INCENP and perhaps other chromosomal passenger proteins.

Supplementary Material

[Supplemental Materials]

ACKNOWLEDGMENTS

We thank the members of the De Lozanne and O'Halloran laboratories for comments and help throughout the development of this project. We also thank the staff of the Protein Analysis Core Facility at University of Texas at Austin for advice on mass spectrometry analysis. This research was supported by grants from the National Institutes of Health to J.A.S. and by GM-48745 to A.D.

Footnotes

This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E06-10-0895) on June 13, 2007.

An external file that holds a picture, illustration, etc.
Object name is dbox.jpgAn external file that holds a picture, illustration, etc.
Object name is vbox.jpg The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

REFERENCES

  • Abaza A., Soleilhac J. M., Westendorf J., Piel M., Crevel I., Roux A., Pirollet F. M phase phosphoprotein 1 is a human plus-end-directed kinesin-related protein required for cytokinesis. J. Biol. Chem. 2003;278:27844–27852. [PMC free article] [PubMed]
  • Adams R. R., Carmena M., Earnshaw W. C. Chromosomal passengers and the (aurora) ABCs of mitosis. Trends Cell Biol. 2001a;11:49–54. [PubMed]
  • Adams R. R., Maiato H., Earnshaw W. C., Carmena M. Essential roles of Drosophila inner centromere protein (INCENP) and Aurora B in histone H3 phosphorylation, metaphase chromosome alignment, kinetochore disjunction, and chromosome segregation. J. Cell Biol. 2001b;153:865–880. [PMC free article] [PubMed]
  • Adams R. R., Tavares A. A., Salzberg A., Bellen H. J., Glover D. M. pavarotti encodes a kinesin-like protein required to organize the central spindle and contractile ring for cytokinesis. Genes Dev. 1998;12:1483–1494. [PMC free article] [PubMed]
  • Adams R. R., Wheatleya S. P., Gouldsworthy A. M., Kandels-Lewis S. E., Carmena M., Smythe C., Gerloff D. L., Earnshaw W. C. INCENP binds the Aurora-related kinase AIRK2 and is required to target it to chromosomes, the central spindle and cleavage furrow. Curr. Biol. 2000;10:1075–1078. [PubMed]
  • Ainsztein A. M., Kandels-Lewis S. E., Mackay A. M., Earnshaw W. C. INCENP centromere and spindle targeting: identification of essential conserved motifs and involvement of heterochromatin protein HP1. J. Cell Biol. 1998;143:1763–1774. [PMC free article] [PubMed]
  • Bishop J. D., Schumacher J. M. Phosphorylation of the carboxyl terminus of inner centromere protein (INCENP) by the Aurora B Kinase stimulates Aurora B kinase activity. J. Biol. Chem. 2002;277:27577–27580. [PMC free article] [PubMed]
  • Bolton M. A., Lan W., Powers S. E., McCleland M. L., Kuang J., Stukenberg P. T. Aurora B kinase exists in a complex with Survivin and INCENP and its kinase activity is stimulated by Survivin binding and phosphorylation. Mol. Biol. Cell. 2002;13:3064–3077. [PMC free article] [PubMed]
  • Bretschneider T., Jonkman J., Kohler J., Medalia O., Barisic K., Weber I., Stelzer E. H., Baumeister W., Gerisch G. Dynamic organization of the actin system in the motile cells of Dictyostelium. J. Muscle Res. Cell Motil. 2002;23:639–649. [PubMed]
  • Cardelli J. Phagocytosis and macropinocytosis in Dictyostelium: phosphoinositide-based processes, biochemically distinct. Traffic. 2001;2:311–320. [PubMed]
  • Cheeseman I. M., Anderson S., Jwa M., Green E. M., Kang J., Yates J. R., 3rd, Chan C. S., Drubin D. G., Barnes G. Phospho-regulation of kinetochore-microtubule attachments by the Aurora kinase Ipl1p. Cell. 2002;111:163–172. [PubMed]
  • Chen Q., Li H., De Lozanne A. Contractile ring-independent localization of DdINCENP, a protein important for spindle stability and cytokinesis. Mol. Biol. Cell. 2006;17:779–788. [PMC free article] [PubMed]
  • Cooke C. A., Heck M.M.S., Earnshaw W. C. The inner centromere protein (INCENP) antigens: movement from inner centromere to midbody during mitosis. J. Cell Biol. 1987;105:2053–2067. [PMC free article] [PubMed]
  • Dean S. O., Rogers S. L., Stuurman N., Vale R. D., Spudich J. A. Distinct pathways control recruitment and maintenance of myosin II at the cleavage furrow during cytokinesis. Proc. Natl. Acad. Sci. USA. 2005;102:13473–13478. [PMC free article] [PubMed]
  • Demma M., Warren V., Hock R., Dharmawardhane S., Condeelis J. Isolation of an abundant 50,000-dalton actin filament bundling protein from Dictyostelium amoebae. J. Biol. Chem. 1990;265:2286–2291. [PubMed]
  • Dharmawardhane S., Demma M., Yang F., Condeelis J. Compartmentalization and actin binding properties of ABP-50, the elongation factor-1 alpha of Dictyostelium. Cell Motil. Cytoskeleton. 1991;20:279–288. [PubMed]
  • Earnshaw W. C., Cooke C. A. Analysis of the distribution of INCENPs throughout mitosis reveals the existence of a pathway of structural changes in the chromosomes during metaphase and early events in cleavage furrow formation. J. Cell Sci. 1991;98:443–461. [PubMed]
  • Echard A., Jollivet F., Martinez O., Lacapere J. J., Rousselet A., Janoueix-Lerosey I., Goud B. Interaction of a Golgi-associated kinesin-like protein with Rab6. Science. 1998;279:580–585. [PubMed]
  • Eckley D. M., Ainsztein A. M., Mackay A. M., Goldberg I. G., Earnshaw W. C. Chromosomal proteins and cytokinesis: patterns of cleavage furrow formation and inner centromere protein positioning in mitotic heterokaryons and mid-anaphase cells. J. Cell Biol. 1997;136:1169–1183. [PMC free article] [PubMed]
  • Gassmann R., Carvalho A., Henzing A. J., Ruchaud S., Hudson D. F., Honda R., Nigg E. A., Gerloff D. L., Earnshaw W. C. Borealin: a novel chromosomal passenger required for stability of the bipolar mitotic spindle. J. Cell Biol. 2004;166:179–191. [PMC free article] [PubMed]
  • Gerald N., Dai J., Ting-Beall H. P., De Lozanne A. A role for Dictyostelium racE in cortical tension and cleavage furrow progression. J. Cell Biol. 1998;141:483–492. [PMC free article] [PubMed]
  • Gerald N., Damer C. K., O'Halloran T. J., De Lozanne A. Cytokinesis failure in clathrin-minus cells is caused by cleavage furrow instability. Cell Motil. Cytoskeleton. 2001;48:213–223. [PubMed]
  • Giet R., Glover D. M. Drosophila Aurora B kinase is required for histone H3 phosphorylation and condensin recruitment during chromosome condensation and to organize the central spindle during cytokinesis. J. Cell Biol. 2001;152:669–682. [PMC free article] [PubMed]
  • Gruneberg U., Neef R., Honda R., Nigg E. A., Barr F. A. Relocation of Aurora B from centromeres to the central spindle at the metaphase to anaphase transition requires MKlp2. J. Cell Biol. 2004;166:167–172. [PMC free article] [PubMed]
  • Haus U., Trommler P., Fisher P. R., Hartmann H., Lottspeich F., Noegel A. A., Schleicher M. The heat shock cognate protein from Dictyostelium affects actin polymerization through interaction with the actin-binding protein cap32/34. EMBO J. 1993;12:3763–3771. [PMC free article] [PubMed]
  • Hill E., Clarke M., Barr F. A. The Rab6-binding kinesin, Rab6-KIFL, is required for cytokinesis. EMBO J. 2000;19:5711–5719. [PMC free article] [PubMed]
  • Honda R., Korner R., Nigg E. A. Exploring the functional interactions between Aurora B, INCENP, and Survivin in mitosis. Mol. Biol. Cell. 2003;14:3325–3341. [PMC free article] [PubMed]
  • Kaitna S., Mendoza M., Jantsch-Plunger V., Glotzer M. INCENP and an Aurora-like kinase form a complex essential for chromosome segregation and efficient completion of cytokinesis. Curr. Biol. 2000;10:1172–1181. [PubMed]
  • Kang J. S., Cheeseman I. M., Kallstrom G., Velmurugan S., Barnes G., Chan C. S. Functional cooperation of Dam1, Ipl1, and the inner centromere protein (INCENP)-related protein Sli15 during chromosome segregation. J. Cell Biol. 2001;155:763–774. [PMC free article] [PubMed]
  • Kim J. H., Kang J. S., Chan C. S. Sli15 associates with the ipl1 protein kinase to promote proper chromosome segregation in Saccharomyces cerevisiae. J. Cell Biol. 1999;145:1381–1394. [PMC free article] [PubMed]
  • Klein U. R., Nigg E. A., Gruneberg U., Zheng Y. Centromere targeting of the chromosomal passenger complex requires a ternary subcomplex of Borealin, Survivin, and the N-terminal domain of INCENP. Mol. Biol. Cell. 2006;17:2547–2558. [PMC free article] [PubMed]
  • Koch K. V., Reinders Y., Ho T. H., Sickmann A., Graf R. Identification and isolation of Dictyostelium microtubule-associated protein interactors by tandem affinity purification. Eur. J. Cell Biol. 2006;85:1079–1090. [PubMed]
  • Kollmar M., Glockner G. Identification and phylogenetic analysis of Dictyostelium discoideum kinesin proteins. BMC Genomics. 2003;4:47. [PMC free article] [PubMed]
  • Konzok A., Weber I., Simmeth E., Hacker U., Maniak M., Muller-Taubenberger A. DAip1, a Dictyostelium homologue of the yeast actin-interacting protein 1, is involved in endocytosis, cytokinesis, and motility. J. Cell Biol. 1999;146:453–464. [PMC free article] [PubMed]
  • Koonce M. P., McIntosh J. R. Identification and immunolocalization of cytoplasmic dynein in Dictyostelium. Cell Motil. Cytoskeleton. 1990;15:51–62. [PubMed]
  • Kuriyama R., Gustus C., Terada Y., Uetake Y., Matuliene J. CHO1, a mammalian kinesin-like protein, interacts with F-actin and is involved in the terminal phase of cytokinesis. J. Cell Biol. 2002;156:783–790. [PMC free article] [PubMed]
  • Lakshmikanth G. S., Warrick H. M., Spudich J. A. A mitotic kinesin-like protein required for normal karyokinesis, myosin localization to the furrow, and cytokinesis in Dictyostelium. Proc. Natl. Acad. Sci. USA. 2004;101:16519–16524. [PMC free article] [PubMed]
  • Mackay A. M., Ainsztein A. M., Eckley D. M., Earnshaw W. C. A dominant mutant of inner centromere protein (INCENP), a chromosomal protein, disrupts prometaphase congression and cytokinesis. J. Cell Biol. 1998;140:991–1002. [PMC free article] [PubMed]
  • Matuliene J., Kuriyama R. Kinesin-like protein CHO1 is required for the formation of midbody matrix and the completion of cytokinesis in mammalian cells. Mol. Biol. Cell. 2002;13:1832–1845. [PMC free article] [PubMed]
  • McIntosh J. R., Roos U. P., Neighbors B., McDonald K. L. Architecture of the microtubule component of mitotic spindles from Dictyostelium discoideum. J. Cell Sci. 1985;75:93–129. [PubMed]
  • Miki H., Setou M., Kaneshiro K., Hirokawa N. All kinesin superfamily protein, KIF, genes in mouse and human. Proc. Natl. Acad. Sci. USA. 2001;98:7004–7011. [PMC free article] [PubMed]
  • Mishima M., Kaitna S., Glotzer M. Central spindle assembly and cytokinesis require a kinesin-like protein/RhoGAP complex with microtubule bundling activity. Dev Cell. 2002;2:41–54. [PubMed]
  • Mishima M., Pavicic V., Gruneberg U., Nigg E. A., Glotzer M. Cell cycle regulation of central spindle assembly. Nature. 2004;430:908–913. [PubMed]
  • Mollinari C., et al. The mammalian passenger protein TD-60 is an RCC1 family member with an essential role in prometaphase to metaphase progression. Dev. Cell. 2003;5:295–307. [PubMed]
  • Neef R., Preisinger C., Sutcliffe J., Kopajtich R., Nigg E. A., Mayer T. U., Barr F. A. Phosphorylation of mitotic kinesin-like protein 2 by polo-like kinase 1 is required for cytokinesis. J. Cell Biol. 2003;162:863–875. [PMC free article] [PubMed]
  • Nislow C., Lombillo V. A., Kuriyama R., McIntosh J. R. A plus-end-directed motor enzyme that moves antiparallel microtubules in vitro localizes to the interzone of mitotic spindles. Nature. 1992;359:543–547. [PubMed]
  • Pereira G., Schiebel E. Separase regulates INCENP-Aurora B anaphase spindle function through Cdc14. Science. 2003;302:2120–2124. [PubMed]
  • Raich W. B., Moran A. N., Rothman J. H., Hardin J. Cytokinesis and midzone microtubule organization in Caenorhabditis elegans require the kinesin-like protein ZEN-4. Mol. Biol. Cell. 1998;9:2037–2049. [PMC free article] [PubMed]
  • Rigaut G., Shevchenko A., Rutz B., Wilm M., Mann M., Seraphin B. A generic protein purification method for protein complex characterization and proteome exploration. Nat. Biotechnol. 1999;17:1030–1032. [PubMed]
  • Rivero F., Illenberger D., Somesh B. P., Dislich H., Adam N., Meyer A. K. Defects in cytokinesis, actin reorganization and the contractile vacuole in cells deficient in RhoGDI. EMBO J. 2002;21:4539–4549. [PMC free article] [PubMed]
  • Romano A., Guse A., Krascenicova I., Schnabel H., Schnabel R., Glotzer M. CSC-1, a subunit of the Aurora B kinase complex that binds to the Survivin-like protein BIR-1 and the INCENP-like protein ICP-1. J. Cell Biol. 2003;161:229–236. [PMC free article] [PubMed]
  • Roos U. P., Camenzind R. Spindle dynamics during mitosis in Dictyostelium discoideum. Eur. J. Cell Biol. 1981;25:248–257. [PubMed]
  • Roos U. P., De Brabander M., De Mey J. Indirect immunofluorescence of microtubules in Dictyostelium discoideum. A study with polyclonal and monoclonal antibodies to tubulins. Exp. Cell Res. 1984;151:183–193. [PubMed]
  • Sampath S. C., Ohi R., Leismann O., Salic A., Pozniakovski A., Funabiki H. The chromosomal passenger complex is required for chromatin-induced microtubule stabilization and spindle assembly. Cell. 2004;118:187–202. [PubMed]
  • Savoian M. S., Earnshaw W. C., Khodjakov A., Rieder C. L. Cleavage furrows formed between centrosomes lacking an intervening spindle and chromosomes contain microtubule bundles, INCENP, and CHO1 but not CENP-E. Mol. Biol. Cell. 1999;10:297–311. [PMC free article] [PubMed]
  • Shevchenko A., Wilm M., Vorm O., Mann M. Mass spectrometric sequencing of proteins silver-stained polyacrylamide gels. Anal. Chem. 1996;68:850–858. [PubMed]
  • Tanaka T. U., Rachidi N., Janke C., Pereira G., Galova M., Schiebel E., Stark M. J., Nasmyth K. Evidence that the Ipl1-Sli15 (Aurora kinase-INCENP) complex promotes chromosome bi-orientation by altering kinetochore-spindle pole connections. Cell. 2002;108:317–329. [PubMed]
  • Wheatley S. P., Carvalho A., Vagnarelli P., Earnshaw W. C. INCENP is required for proper targeting of Survivin to the centromeres and the anaphase spindle during mitosis. Curr. Biol. 2001;11:886–890. [PubMed]

Articles from Molecular Biology of the Cell are provided here courtesy of American Society for Cell Biology
PubReader format: click here to try

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...