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Mol Cell. 2007 Dec 28;28(6):1029-44.

A NASP (N1/N2)-related protein, Sim3, binds CENP-A and is required for its deposition at fission yeast centromeres.

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  • 1Wellcome Trust Centre for Cell Biology and Institute of Cell Biology, School of Biological Sciences, The University of Edinburgh, 6.34 Swann Building, Edinburgh EH9 3JR, Scotland, UK.

Abstract

A defining feature of centromeres is the presence of the histone H3 variant CENP-A(Cnp1). It is not known how CENP-A(Cnp1) is specifically delivered to, and assembled into, centromeric chromatin. Through a screen for factors involved in kinetochore integrity in fission yeast, we identified Sim3. Sim3 is homologous to known histone binding proteins NASP(Human) and N1/N2(Xenopus) and aligns with Hif1(S. cerevisiae), defining the SHNi-TPR family. Sim3 is distributed throughout the nucleoplasm, yet it associates with CENP-A(Cnp1) and also binds H3. Cells defective in Sim3 function have reduced levels of CENP-A(Cnp1) at centromeres (and increased H3) and display chromosome segregation defects. Sim3 is required to allow newly synthesized CENP-A(Cnp1) to accumulate at centromeres in S and G2 phase-arrested cells in a replication-independent mechanism. We propose that one function of Sim3 is to act as an escort that hands off CENP-A(Cnp1) to chromatin assembly factors, allowing its incorporation into centromeric chromatin.

PMID:
18158900
[PubMed - indexed for MEDLINE]
PMCID:
PMC2193228
Free PMC Article

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