Nonhistone Scm3 Binds to AT-Rich DNA to Organize Atypical Centromeric Nucleosome of Budding Yeast
Nonhistone Scm3 Binds to AT-Rich DNA to Organize Atypical Centromeric Nucleosome of Budding Yeast
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DOI：
10.1016/j.molcel.2011.07.009
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发表时间：
2011-08-05
期刊：
影响因子：
16
通讯作者：
Wu, Carl
中科院分区：
文献类型：
--
作者：
Xiao, Hua;Mizuguchi, Gaku;Wu, Carl
含有组蛋白变体CenH 3的着丝粒特异性核小体的分子结构是有争议的。我们已经生化重建了两个不同的群体的核小体含有酿酒酵母CenH 3（Cse 4）。含有组蛋白Cse 4/H4/H2 A/H2 B的八聚体核小体的重构在非着丝粒DNA上是稳健的，但在富含AT的着丝粒DNA上是低效的。然而，非组蛋白Scm 3，这是所需的Cse 4沉积在体内，促进在体外重建的Cse 4/H4/Scm 3复合物上AT丰富的着丝粒序列。Scm 3具有非特异性DNA结合结构域，其显示对富含AT的DNA的偏好，以及促进Cse 4/H4的特异性装载的组蛋白伴侣结构域。在活细胞中，Scm 3-GFP在所有细胞周期阶段的着丝粒处富集。染色质免疫沉淀证实，Scm 3占据着丝粒DNA在整个细胞周期中，即使Cse 4和H4暂时在S期被逐出。这些研究结果表明，着丝粒结合Scm 3的艾滋病的Cse 4/H4的招聘组装和维持H2 A/H2 B缺陷的着丝粒核小体的模型。
The molecular architecture of centromere-specific nucleosomes containing histone variant CenH3 is controversial. We have biochemically reconstituted two distinct populations of nucleosomes containing Saccharomyces cerevisiae CenH3 (Cse4). Reconstitution of octameric nucleosomes containing histones Cse4/H4/H2A/H2B is robust on noncentromere DNA, but inefficient on AT-rich centromere DNA. However, nonhistone Scm3, which is required for Cse4 deposition in vivo, facilitates in vitro reconstitution of Cse4/H4/Scm3 complexes on AT-rich centromere sequences. Scm3 has a nonspecific DNA binding domain that shows preference for AT-rich DNA and a histone chaperone domain that promotes specific loading of Cse4/H4. In live cells, Scm3-GFP is enriched at centromeres in all cell cycle phases. Chromatin immunoprecipitation confirms that Scm3 occupies centromere DNA throughout the cell cycle, even when Cse4 and H4 are temporarily dislodged in S phase. These findings suggest a model in which centromere-bound Scm3 aids recruitment of Cse4/H4 to assemble and maintain an H2A/H2B-deficient centromeric nucleosome.