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首页> 外文期刊>Biochemistry >Histones in transit: cytosolic histone complexes and diacetylation of H4 during nucleosome assembly in human cells.
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Histones in transit: cytosolic histone complexes and diacetylation of H4 during nucleosome assembly in human cells.

机译：运输中的组蛋白：人细胞核小体组装过程中的胞质组蛋白复合物和H4的二乙酰化。

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The organization and acetylation of nascent histones prior to their stable incorporation into chromatin were examined. Through sedimentation and immunoprecipitation analyses of HeLa cytosolic extracts, two somatic non-nucleosomal histone complexes were detected: one containing nascent H3 and H4, and a second containing H2A (and probably H2B) in association with the nonhistone protein NAP-1. The H3/H4 complex has a sedimentation coefficient of 5-6S, consistent with the presence of one or more escort proteins. H4 in the cytosolic H3/H4 complex is diacetylated, fully in accord with the acetylation state of newly synthesized H4 in chromatin. The diacetylation of nascent human H4 is therefore completed prior to nucleosome assembly. As part of our studies of the nascent H3/H4 complex, the cytoplasmic histone acetyltransferase most likely responsible for acetylating newly synthesized H4 was also investigated. HeLa histone acetyltransferase B (HAT B) acetylates H4 but not H3 in vitro, and maximally diacetylates H4 even in the presence of sodium butyrate. Human HAT B acetylates H4 exclusively on the lysine residues at positions 5 and 12, in complete agreement with the highly conserved acetylation pattern of nascent nucleosomal H4 (Sobel et al., 1995), and has a native molecular weight of approximately 100 kDa. Based on our findings a model is presented for the involvement of histone acetylation and NAP-1 in H2A/H2B deposition and exchange, during nucleosome assembly and chromatin remodeling in vivo.
机译：检查了新生组蛋白在稳定掺入染色质之前的组织和乙酰化。通过HeLa细胞质提取物的沉淀和免疫沉淀分析，检测到两种体细胞非核小体组蛋白复合物：一种含有新生H3和H4，另一种含有H2A（可能还有H2B）与非组蛋白NAP-1结合。 H3 / H4复合物的沉降系数为5-6S，与一种或多种伴游蛋白的存在一致。胞质H3 / H4复合物中的H4被二乙酰化，完全符合染色质中新合成H4的乙酰化状态。因此，在核小体组装之前完成新生人类H4的二乙酰化。作为我们对新生H3 / H4复合物的研究的一部分，还研究了最有可能使新合成的H4乙酰化的胞质组蛋白乙酰转移酶。 HeLa组蛋白乙酰基转移酶B（HAT B）在体外能乙酰化H4，但不能乙酰化H3，即使在丁酸钠存在下，也能最大程度地乙酰化H4。人HAT B仅在5和12位的赖氨酸残基上使H4乙酰化，这与新生的核小体H4的高度保守的乙酰化模式完全一致（Sobel等，1995），其天然分子量约为100 kDa。根据我们的发现，提出了一个模型，用于在体内核小体组装和染色质重塑过程中，组蛋白乙酰化和NAP-1参与H2A / H2B沉积和交换。

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