* 602388

SYMPLEKIN; SYMPK


Alternative titles; symbols

SPK


HGNC Approved Gene Symbol: SYMPK

Cytogenetic location: 19q13.32     Genomic coordinates (GRCh38): 19:45,815,410-45,863,147 (from NCBI)


TEXT

Description

Symplekin is a 150-kD protein associated with the cytoplasmic face of the tight junction-containing zone (zonula occludens) of polar epithelial cells and Sertoli cells of the testis (Keon et al., 1996). Nuclear-localized SYMPK associates with the heterotrimeric cleavage stimulation factor (CSTF; see 300907), which participates in polyadenylation of mRNAs, and may be involved in CSTF assembly (Takagaki and Manley, 2000). SYMPK also plays a critical role in 3-prime end maturation of histone mRNAs (Kolev and Steitz, 2005).


Cloning and Expression

Using an antibody that targeted a 150-kD zonula occludens protein, Keon et al. (1996) screened a human colon carcinoma cDNA expression library and cloned SYMPK. The deduced 1,142-amino acid protein has a calculated molecular mass of 126.5 kD. The N-terminal half of SYMPK has several extended hydrophilic segments, and the C-terminal half has alternating short hydrophobic and hydrophilic stretches. SYMPK also has a possible nuclear localization signal in its N-terminal half and several putative phosphorylation sites spread throughout its sequence. Northern blot analysis detected an approximately 3.7-kb SYMPK transcript in cultured polarized epithelial cells, as well as in adenocarcinomas and several nonepithelial cells. SYMPK was partially extracted in alkaline low salt or high salt buffers, but complete extraction required nonionic detergent solubilization. Immunohistochemical and immunogold electron microscopy detected high SYMPK expression at subapical tight junctions in polarized epithelial cells, where it colocalized with ZO1 (TJP1; 601009). SYMPK also showed intense staining of the nucleoplasm, with exclusion from nucleoli, in all epithelial and nonepithelial cells examined, including uncoupled cells, such as lymphocytes and lymphoma and erythroleukemia cells.

Using Northern blot analysis, Ueki et al. (1997) detected a 4.2-kb SYMPK transcript that was highly expressed in skeletal muscle, with lower expression in brain, heart, liver, placenta, kidney, lung, and pancreas.

By searching for genes within 200 kb of the myotonic dystrophy expanded repeat (DMPK; 605377), followed by RT-PCR of adult human brain, testis, and muscle and database analysis, Alwazzan et al. (1998) identified SYMPK. The transcript has a 5-prime UTR of approximately 60 kb. Northern blot analysis detected a 4.5-kb SYMPK transcript in heart and brain.

Takagaki and Manley (2000) reported that full-length SYMPK has 1,273 amino acids and includes a large N-terminal domain that shares significant similarity with yeast Pta1, a component of the yeast polyadenylation machinery. The Pta1-like domain contains 4 putative nuclear localization signals. Takagaki and Manley (2000) also identified a splice variant of SYMPK that encodes a deduced 1,058-amino acid isoform that is identical to the long isoform for the first 964 amino acids, including the Pta1-like domain. The 2 proteins diverge in their C-terminal sequences.


Gene Function

Takagaki and Manley (2000) found that SYMPK colocalized with the CSTF complex isolated from HeLa cell nuclei. The core CSTF subunits were CSTF50 (CSTF1; 600369), CSTF64 (CSTF2; 300907), and CSTF77 (CSTF3; 600367). SYMPK interacted directly with CSTF64, but it did not associate with the purified CSTF heterotrimer. Takagaki and Manley (2000) proposed that nuclear SYMPK may function as a chaperone in CSTF assembly.

Kolev and Steitz (2005) identified SYMPK as a critical subunit of a large protein complex that functioned in 3-prime end maturation of histone mRNA. Using mouse histone H4-12 pre-mRNA as substrate, they purified a complex that functioned in 3-prime end processing from HeLa cell nuclear extracts. The complex included the cleavage and polyadenylation specificity factor (CPSF) subunits CPSF160 (CPSF1; 606027), CPSF100 (CPSF2; 606028), CPSF73 (CPSF3; 606029), CPSF30 (CPSF4; 603052), and FIP1 (FIP1L1; 607686), in addition to CSTF77, CSTF64, and SYMPK. These 8 proteins have a combined predicted molecular mass of 694 kD, consistent with the complex sedimenting at 14.7S. Heat treatment led to inactivation and dissociation of the complex, concomitant with degradation of SYMPK, which proved to be the heat-labile labile subunit. Addition of recombinant human SYMPK restored processing of mouse H4-12 pre-mRNA by the heat-inactivated complex. Kolev and Steitz (2005) concluded that SYMPK was required for functional complex integrity.


Mapping

In an attempt to identify a putative tumor suppressor gene involved in human gliomas, Ueki et al. (1997) performed exon trapping from cosmids mapping to chromosome 19q13.3 and found 6 exonic sequences that matched the human symplekin gene. A portion of the 5-prime sequence matched an additional trapped exonic sequence that was obtained from the most telomeric cosmid analyzed. They concluded that the symplekin gene lies in a telomeric-to-centromeric orientation on chromosome 19q13.3. They assigned the symplekin gene to a 40-kb region immediately telomeric to gene 59 and the DMPK gene.


REFERENCES

  1. Alwazzan, M., Hamshere, M. G., Lennon, G. G., Brook, J. D. Six transcripts map within 200 kilobases of the myotonic dystrophy expanded repeat. Mammalian Genome 9: 485-487, 1998. [PubMed: 9585442, related citations] [Full Text]

  2. Keon, B. H., Schafer, S., Kuhn, C., Grund, C., Franke, W. W. Symplekin, a novel type of tight junction plaque protein. J. Cell Biol. 134: 1003-1018, 1996. [PubMed: 8769423, related citations] [Full Text]

  3. Kolev, N. G., Steitz, J. A. Symplekin and multiple other polyadenylation factors participate in 3-prime-end maturation of histone mRNAs. Genes Dev. 19: 2583-2592, 2005. [PubMed: 16230528, images, related citations] [Full Text]

  4. Takagaki, Y., Manley, J. L. Complex protein interactions within the human polyadenylation machinery identify a novel component. Molec. Cell. Biol. 20: 1515-1525, 2000. [PubMed: 10669729, images, related citations] [Full Text]

  5. Ueki, K., Ramaswamy, S., Billings, S. J., Mohrenweiser, H. W., Louis, D. N. Chromosomal localization to 19q13.3, partial genomic structure and 5-prime cDNA sequence of the human symplekin gene. Somat. Cell Molec. Genet. 23: 229-231, 1997. [PubMed: 9330635, related citations] [Full Text]


Contributors:
Patricia A. Hartz - updated : 6/5/2014
Creation Date:
Victor A. McKusick : 2/24/1998
mgross : 06/06/2014
mgross : 6/5/2014
mcolton : 5/30/2014
carol : 4/15/2014
dholmes : 4/17/1998
mark : 2/24/1998

* 602388

SYMPLEKIN; SYMPK


Alternative titles; symbols

SPK


HGNC Approved Gene Symbol: SYMPK

Cytogenetic location: 19q13.32     Genomic coordinates (GRCh38): 19:45,815,410-45,863,147 (from NCBI)


TEXT

Description

Symplekin is a 150-kD protein associated with the cytoplasmic face of the tight junction-containing zone (zonula occludens) of polar epithelial cells and Sertoli cells of the testis (Keon et al., 1996). Nuclear-localized SYMPK associates with the heterotrimeric cleavage stimulation factor (CSTF; see 300907), which participates in polyadenylation of mRNAs, and may be involved in CSTF assembly (Takagaki and Manley, 2000). SYMPK also plays a critical role in 3-prime end maturation of histone mRNAs (Kolev and Steitz, 2005).


Cloning and Expression

Using an antibody that targeted a 150-kD zonula occludens protein, Keon et al. (1996) screened a human colon carcinoma cDNA expression library and cloned SYMPK. The deduced 1,142-amino acid protein has a calculated molecular mass of 126.5 kD. The N-terminal half of SYMPK has several extended hydrophilic segments, and the C-terminal half has alternating short hydrophobic and hydrophilic stretches. SYMPK also has a possible nuclear localization signal in its N-terminal half and several putative phosphorylation sites spread throughout its sequence. Northern blot analysis detected an approximately 3.7-kb SYMPK transcript in cultured polarized epithelial cells, as well as in adenocarcinomas and several nonepithelial cells. SYMPK was partially extracted in alkaline low salt or high salt buffers, but complete extraction required nonionic detergent solubilization. Immunohistochemical and immunogold electron microscopy detected high SYMPK expression at subapical tight junctions in polarized epithelial cells, where it colocalized with ZO1 (TJP1; 601009). SYMPK also showed intense staining of the nucleoplasm, with exclusion from nucleoli, in all epithelial and nonepithelial cells examined, including uncoupled cells, such as lymphocytes and lymphoma and erythroleukemia cells.

Using Northern blot analysis, Ueki et al. (1997) detected a 4.2-kb SYMPK transcript that was highly expressed in skeletal muscle, with lower expression in brain, heart, liver, placenta, kidney, lung, and pancreas.

By searching for genes within 200 kb of the myotonic dystrophy expanded repeat (DMPK; 605377), followed by RT-PCR of adult human brain, testis, and muscle and database analysis, Alwazzan et al. (1998) identified SYMPK. The transcript has a 5-prime UTR of approximately 60 kb. Northern blot analysis detected a 4.5-kb SYMPK transcript in heart and brain.

Takagaki and Manley (2000) reported that full-length SYMPK has 1,273 amino acids and includes a large N-terminal domain that shares significant similarity with yeast Pta1, a component of the yeast polyadenylation machinery. The Pta1-like domain contains 4 putative nuclear localization signals. Takagaki and Manley (2000) also identified a splice variant of SYMPK that encodes a deduced 1,058-amino acid isoform that is identical to the long isoform for the first 964 amino acids, including the Pta1-like domain. The 2 proteins diverge in their C-terminal sequences.


Gene Function

Takagaki and Manley (2000) found that SYMPK colocalized with the CSTF complex isolated from HeLa cell nuclei. The core CSTF subunits were CSTF50 (CSTF1; 600369), CSTF64 (CSTF2; 300907), and CSTF77 (CSTF3; 600367). SYMPK interacted directly with CSTF64, but it did not associate with the purified CSTF heterotrimer. Takagaki and Manley (2000) proposed that nuclear SYMPK may function as a chaperone in CSTF assembly.

Kolev and Steitz (2005) identified SYMPK as a critical subunit of a large protein complex that functioned in 3-prime end maturation of histone mRNA. Using mouse histone H4-12 pre-mRNA as substrate, they purified a complex that functioned in 3-prime end processing from HeLa cell nuclear extracts. The complex included the cleavage and polyadenylation specificity factor (CPSF) subunits CPSF160 (CPSF1; 606027), CPSF100 (CPSF2; 606028), CPSF73 (CPSF3; 606029), CPSF30 (CPSF4; 603052), and FIP1 (FIP1L1; 607686), in addition to CSTF77, CSTF64, and SYMPK. These 8 proteins have a combined predicted molecular mass of 694 kD, consistent with the complex sedimenting at 14.7S. Heat treatment led to inactivation and dissociation of the complex, concomitant with degradation of SYMPK, which proved to be the heat-labile labile subunit. Addition of recombinant human SYMPK restored processing of mouse H4-12 pre-mRNA by the heat-inactivated complex. Kolev and Steitz (2005) concluded that SYMPK was required for functional complex integrity.


Mapping

In an attempt to identify a putative tumor suppressor gene involved in human gliomas, Ueki et al. (1997) performed exon trapping from cosmids mapping to chromosome 19q13.3 and found 6 exonic sequences that matched the human symplekin gene. A portion of the 5-prime sequence matched an additional trapped exonic sequence that was obtained from the most telomeric cosmid analyzed. They concluded that the symplekin gene lies in a telomeric-to-centromeric orientation on chromosome 19q13.3. They assigned the symplekin gene to a 40-kb region immediately telomeric to gene 59 and the DMPK gene.


REFERENCES

  1. Alwazzan, M., Hamshere, M. G., Lennon, G. G., Brook, J. D. Six transcripts map within 200 kilobases of the myotonic dystrophy expanded repeat. Mammalian Genome 9: 485-487, 1998. [PubMed: 9585442] [Full Text: https://doi.org/10.1007/s003359900804]

  2. Keon, B. H., Schafer, S., Kuhn, C., Grund, C., Franke, W. W. Symplekin, a novel type of tight junction plaque protein. J. Cell Biol. 134: 1003-1018, 1996. [PubMed: 8769423] [Full Text: https://doi.org/10.1083/jcb.134.4.1003]

  3. Kolev, N. G., Steitz, J. A. Symplekin and multiple other polyadenylation factors participate in 3-prime-end maturation of histone mRNAs. Genes Dev. 19: 2583-2592, 2005. [PubMed: 16230528] [Full Text: https://doi.org/10.1101/gad.1371105]

  4. Takagaki, Y., Manley, J. L. Complex protein interactions within the human polyadenylation machinery identify a novel component. Molec. Cell. Biol. 20: 1515-1525, 2000. [PubMed: 10669729] [Full Text: https://doi.org/10.1128/MCB.20.5.1515-1525.2000]

  5. Ueki, K., Ramaswamy, S., Billings, S. J., Mohrenweiser, H. W., Louis, D. N. Chromosomal localization to 19q13.3, partial genomic structure and 5-prime cDNA sequence of the human symplekin gene. Somat. Cell Molec. Genet. 23: 229-231, 1997. [PubMed: 9330635] [Full Text: https://doi.org/10.1007/BF02721375]


Contributors:
Patricia A. Hartz - updated : 6/5/2014

Creation Date:
Victor A. McKusick : 2/24/1998

Edit History:
mgross : 06/06/2014
mgross : 6/5/2014
mcolton : 5/30/2014
carol : 4/15/2014
dholmes : 4/17/1998
mark : 2/24/1998