CENP-C facilitates the recruitment of M18BP1 to centromeric chromatin

Abstract

Centromeres are important structural constituents of chromosomes that ensure proper chromosome segregation during mitosis by providing defined sites for kinetochore attachment. In higher eukaryotes, centromeres have no specific DNA sequence and thus, they are rather determined through epigenetic mechanisms. A fundamental process in centromere establishment is the incorporation of the histone variant CENP-A into centromeric chromatin, which provides a binding platform for the other centromeric proteins. The Mis18 complex, and, in particular, its member M18BP1 was shown to be essential for both incorporation and maintenance of CENP-A. Here we show that M18BP1 displays a cell cycle-regulated association with centromeric chromatin in mouse embryonic stem cells. M18BP1 is highly enriched at centromeric regions from late anaphase through to G1 phase. An interaction screen against 16 core centromeric proteins revealed a novel interaction of M18BP1 with CENP-C. We mapped the interaction domain in M18BP1 to a central region containing a conserved SANT domain and in CENP-C to the C-terminus. Knock-down of CENP-C leads to reduced M18BP1 association and lower CENP-A levels at centromeres, suggesting that CENP-C works as an important factor for centromeric M18BP1 recruitment and thus for maintaining centromeric CENP-A.

The distinct functions of CENP-C and CENP-T/W in centromere propagation and function inXenopusegg extracts

“…30,31 The contribution of CENP-N to the CENP-A deposition pathway is unknown whereas CENP-C has been proposed to drive HJURP targeting to centromeres through the Mis18 complex. 33,34 CENP-T and CENP-W do not bind CENP-A but instead recognize H3 nucleosomes present in centromeric chromatin. 35,36 These two proteins together with CENP-S and CENP-X, all 4 containing histone-fold domains, have been proposed to form a nucleosome-like particle capable of supercoiling DNA in vitro.…”

The Centromere: Epigenetic Control of Chromosome Segregation during Mitosis

“…Mis18a, Mis18b, and M18BP1 are recruited to centromeres at an early stage in CENP-A assembly, during anaphase/telophase of mitosis and in early G 1 (Fujita et al 2007;Maddox et al 2007;Dambacher et al 2012). The Mis18 complex is required for the recruitment of HJURP to centromeres in a number of model organisms Williams et al 2009;Barnhart et al 2011;Moree et al 2011), and in human cells, depletion of HJURP has no effect on Mis18a.…”

The role of the Mis18α-β complex and its interactions with HJURP and CENP-A in human centromeric chromatin establishment

“…CENP-C has also been shown to interact with other centromere licensing proteins such as the Mis18 complex. In particular Mis18BP1 interaction with CENP-C has been shown in humans, mice, and Xenopus 65,67 . Indeed CENP-C is so conserved and important for CENP-A deposition it is even still present and required for CENP-A/CID loading in Drosophila, an organism that lacks the Mis18 complex altogether.…”

“…Xenopus there are two isoforms of Mis18BP1 that localize to the centromeres, one of these isoforms is not affected by CENP-C knockdown but is not conserved across species 65,67 . While these researchers put forth a model that CENP-C recruits Mis18BP1, which then recruits both Mis18α and Mis18β, work from our lab shows this is not the whole story.…”

“…In vitro analysis has revealed CENP-C directly binds to CENP-A nucleosomes along with CENP-N, albeit at two different interfaces of CENP-A 17,18 . Further research has shown CENP-C is absolutely required for CENP-A deposition 17,65,66 . CENP-C has also been shown to interact with other centromere licensing proteins such as the Mis18 complex.…”