Centromeres are maintained epigenetically by the presence of CENP-A, an evolutionarily conserved histone H3 variant, which directs kinetochore assembly and hence centromere function. To identify factors that promote assembly of CENP-A chromatin, we affinity-selected solubilized fission yeast CENP-ACnp1 chromatin. All subunits of the Ino80 complex were enriched, including the auxiliary subunit Hap2. Chromatin association of Hap2 is Ies4-dependent. In addition to a role in maintenance of CENP-ACnp1 chromatin integrity at endogenous centromeres, Hap2 is required for de novo assembly of CENP-ACnp1 chromatin on naïve centromere DNA and promotes H3 turnover on centromere regions and other loci prone to CENP-ACnp1 deposition. Prior to CENP-ACnp1 chromatin assembly, Hap2 facilitates transcription from centromere DNA. These analyses suggest that Hap2-Ino80 destabilizes H3 nucleosomes on centromere DNA through transcription-coupled histone H3 turnover, driving the replacement of resident H3 nucleosomes with CENP-ACnp1 nucleosomes. These inherent properties define centromere DNA by directing a program that mediates CENP-ACnp1 assembly on appropriate sequences.

中文翻译：

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Hap2-Ino80 促进转录促进 CENP-A 染色质的从头建立。

着丝粒由 CENP-A 的存在表观遗传维持，CENP-A 是一种进化上保守的组蛋白 H3 变体，它指导着丝粒组装，从而指导着丝粒功能。为了确定促进 CENP-A 染色质组装的因素，我们亲和选择了溶解的裂殖酵母 CENP-ACnp1 染色质。Ino80 复合体的所有亚基都得到了丰富，包括辅助亚基 Hap2。Hap2 的染色质关联依赖于 Ies4。除了在内源着丝粒处维持 CENP-ACnp1 染色质完整性的作用外，Hap2 是 CENP-ACnp1 染色质在幼稚着丝粒 DNA 上的从头组装所必需的，并促进着丝粒区域和其他易于 CENP-ACnp1 沉积的位点的 H3 周转。在 CENP-ACnp1 染色质组装之前，Hap2 促进着丝粒 DNA 的转录。这些分析表明，Hap2-Ino80 通过转录偶联的组蛋白 H3 周转使着丝粒 DNA 上的 H3 核小体不稳定，从而驱动常驻 H3 核小体被 CENP-ACnp1 核小体取代。这些固有特性通过指导一个程序来定义着丝粒 DNA，该程序在适当的序列上介导 CENP-ACnp1 组装。