Histone acetyltransferase 1 (Hat1) catalyzes the acetylation of newly synthesized histone H4 at lysines 5 and 12 that accompanies replication-coupled chromatin assembly. The acetylation of newly synthesized H4 occurs in the cytoplasm and the function of this acetylation is typically ascribed to roles in either histone nuclear import or deposition. Using cell lines from Hat1^+/+ and Hat1^−/− mouse embryos, we demonstrate that Hat1 is not required for either histone nuclear import or deposition. We employed quantitative proteomics to characterize Hat1-dependent changes in the composition of nascent chromatin structure. Among the proteins depleted from nascent chromatin isolated from Hat1^−/− cells are several bromodomain-containing proteins, including Brg1, Baz1A and Brd3. Analysis of the binding specificity of their bromodomains suggests that Hat1-dependent acetylation of H4 is directly involved in their recruitment. Hat1^−/− nascent chromatin is enriched for topoisomerase 2α and 2β. The enrichment of topoisomerase 2 is functionally relevant as Hat1^−/− cells are hyper-sensitive to topoisomerase 2 inhibition suggesting that Hat1 is required for proper chromatin topology. In addition, our results indicate that Hat1 is transiently recruited to sites of chromatin assembly, dissociating prior to the maturation of chromatin structure.

中文翻译：

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鉴定组蛋白乙酰转移酶1在复制偶联染色质组装中的多种作用

组蛋白乙酰基转移酶1（Hat1）催化赖氨酸5和12上新合成的组蛋白H4的乙酰化，其伴随着复制耦合的染色质组装。新合成的H4的乙酰化发生在细胞质中，这种乙酰化的功能通常归因于组蛋白核输入或沉积中的作用。使用来自Hat1 ^{+ / +}和Hat1 ^-/-小鼠胚胎的细胞系，我们证明了组蛋白核的导入或沉积都不需要Hat1。我们采用定量蛋白质组学来表征新生染色质结构组成中Hat1依赖性的变化。在从Hat1 ^-/-分离的新生染色质中消耗的蛋白质中细胞是几种含溴结构域的蛋白质，包括Brg1，Baz1A和Brd3。对它们的溴结构域的结合特异性的分析表明，H4的Hat1依赖性乙酰化直接参与了它们的募集。Hat1 ^-/-新生染色质富含拓扑异构酶2α和2β。拓扑异构酶2的富集与功能相关，因为Hat1 ^-/-细胞对拓扑异构酶2抑制非常敏感，表明Hat1是正确的染色质拓扑所必需的。此外，我们的结果表明Hat1被短暂地募集到染色质装配位点，在染色质结构成熟之前解离。