Okada Masahiro, Okawa Katsuya, Isobe Toshiaki, Fukagawa Tatsuo
*Center for Priority Areas, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; Department of Chemistry, Graduate School of Sciences and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; Innovative Drug Research Laboratories, Kyowa Hakko Kirin Co., Ltd., Takasaki, Gumma, 370-1295, Japan.
Mol Biol Cell. 2009 Sep;20(18):3986-95. doi: 10.1091/mbc.e09-01-0065. Epub 2009 Jul 22.
Centromere identity is thought to be determined by epigenetic mechanisms. The centromere-specific histone H3 variant CENP-A plays a central role in specifying the locus where the centromere is constructed. However, the precise mechanisms that target CENP-A to centromeric chromatin are poorly understood. Here, we show that facilitates chromatin transcription (FACT) localizes to centromeres in a CENP-H-containing complex-dependent manner. In conditional mutant cell lines for SSRP1, a subunit of FACT, centromere targeting of newly synthesized CENP-A is severely inhibited. The chromatin remodeling factor CHD1 binds to SSRP1 both in vivo and in vitro and associates with centromeres. The centromeric localization of CHD1 is lost in SSRP1-depleted cells. RNA interference knockdown of CHD1 leads to a decrease in the amount of centromere localized CENP-A. These findings indicate that the CENP-H-containing complex facilitates deposition of newly synthesized CENP-A into centromeric chromatin in cooperation with FACT and CHD1.
着丝粒身份被认为是由表观遗传机制决定的。着丝粒特异性组蛋白H3变体CENP-A在指定着丝粒构建位点方面发挥着核心作用。然而,将CENP-A靶向着丝粒染色质的精确机制仍知之甚少。在这里,我们表明促进染色质转录(FACT)以依赖于含CENP-H的复合物的方式定位于着丝粒。在FACT的一个亚基SSRP1的条件突变细胞系中,新合成的CENP-A对着丝粒的靶向作用受到严重抑制。染色质重塑因子CHD1在体内和体外均与SSRP1结合,并与着丝粒相关联。在SSRP1缺失的细胞中,CHD1的着丝粒定位丧失。RNA干扰敲低CHD1会导致着丝粒定位的CENP-A数量减少。这些发现表明,含CENP-H的复合物与FACT和CHD1协同作用,促进新合成的CENP-A沉积到着丝粒染色质中。