Equal distribution of DNA in mitosis requires the assembly of a large proteinaceous ensemble onto the centromeric DNA, called the kinetochore. With few exceptions, kinetochore specification is independent of the DNA sequence and is determined epigenetically by deposition at the centromeric chromatin of special nucleosomes containing an H3-related histone, CENP-A. Onto centromeric CENP-A chromatin is assembled the so-called constitutive centromere-associated network (CCAN) of 16 proteins distributed in several functional groups as follows: CENP-C, CENP-H/CENP-I/CENP-K/, CENP-L/CENP-M/CENP-N, CENP-O/CENP-P/CENP-Q/CENP-R/CENP-U(50), CENP-T/CENP-W, and CENP-S/CENP-X. One role of the CCAN is to recruit outer kinetochore components further, such as KNL1, the Mis12 complex, and the Ndc80 complex (KMN network) to which attach the spindle microtubules with their structural and regulatory proteins. Among the CENPs in CCAN, CENP-C and CENP-T are required in parallel for operational kinetochore specification and spindle attachment. This review presents discussion of the latest structural and functional data on CENP-A and CENPs from the CCAN as well as their interaction with the KMN network.

Centromeres are chromosomal structures required for equal DNA segregation to daughter cells, comprising specialized nucleosomes containing centromere protein A (CENP-A) histone, which provide the basis for centromeric chromatin assembly. Discovery of centromere protein components is progressing, but knowledge related to their establishment and maintenance remains limited. Previously, using anti-CENP-A native chromatin immunoprecipitation, we isolated the interphase–centromere complex (ICEN). Among ICEN components, subunits of the remodeling and spacing factor (RSF) complex, Rsf-1 and SNF2h proteins, were found. This paper describes the relationship of the RSF complex to centromere structure and function, demonstrating its requirement for maintenance of CENP-A at the centromeric core chromatin in HeLa cells. The RSF complex interacted with CENP-A chromatin in mid-G1. Rsf-1 depletion induced loss of centromeric CENP-A, and purified RSF complex reconstituted and spaced CENP-A nucleosomes in vitro. From these data, we propose the RSF complex as a new factor actively supporting the assembly of CENP-A chromatin.

HJURP exhibits a centromere expansion activity that is separable from its CENP-A–binding activity. It is proposed that this centromere expansion activity reflects the functional properties of HJURP, which uses this activity to contribute to the plastic establishment of a centromeric chromatin structure.

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