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EMBO J. 2006 Jun 21;25(12):2814-27. Epub 2006 Jun 8.

Misorientation and reduced stretching of aligned sister kinetochores promote chromosome missegregation in EB1- or APC-depleted cells.

Author information

1
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Abstract

The correct formation of stable but dynamic links between chromosomes and spindle microtubules (MTs) is essential for accurate chromosome segregation. However, the molecular mechanisms by which kinetochores bind MTs and checkpoints monitor this binding remain poorly understood. In this paper, we analyze the functions of six kinetochore-bound MT-associated proteins (kMAPs) using RNAi, live-cell microscopy and quantitative image analysis. We find that RNAi-mediated depletion of two kMAPs, the adenomatous polyposis coli protein (APC) and its binding partner, EB1, are unusual in affecting the movement and orientation of paired sister chromatids at the metaphase plate without perturbing kinetochore-MT attachment per se. Quantitative analysis shows that misorientation phenotypes in metaphase are uniform across chromatid pairs even though chromosomal loss (CIN) during anaphase is sporadic. However, errors in kinetochore function generated by APC or EB1 depletion are detected poorly if at all by the spindle checkpoint, even though they cause chromosome missegregation. We propose that impaired EB1 or APC function generates lesions invisible to the spindle checkpoint and thereby promotes low levels of CIN expected to fuel aneuploidy and possibly tumorigenesis.

PMID:
16763565
PMCID:
PMC1500857
DOI:
10.1038/sj.emboj.7601168
[Indexed for MEDLINE]
Free PMC Article

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