NuA4-dependent Acetylation of Nucleosomal Histones H4 and H2A Directly Stimulates Incorporation of H2A.Z by the SWR1 Complex
NuA4-dependent Acetylation of Nucleosomal Histones H4 and H2A Directly Stimulates Incorporation of H2A.Z by the SWR1 Complex
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DOI：
10.1074/jbc.m110.117069
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发表时间：
2010-05-21
影响因子：
4.8
通讯作者：
Cote, Jacques
中科院分区：
文献类型：
--
作者：
Altaf, Mohammed;Auger, Andreanne;Cote, Jacques
在过去的几年中，含有组蛋白变体H2A.Z的核小体的结构和功能分析吸引了很大的兴趣。出现酵母中的重要工作表明，含H2A.Z（HTZ1） - 含有核小体特异性位于基因的启动子区域上，创建了特定的染色质结构，该结构有望在转录激活过程中拆卸。 SWR1复合物负责通过ATP依赖性交换HTZ1-H2B二聚体的ATP依赖性交换将HTZ1掺入核小体中。有趣的是，酵母SWR1复合物在体内与NUA4乙酰基转移酶复合酶的功能相关。 NUA4和SWR1与TIP60/P400复合物同源，在较高的真核生物中与较高的真核生物相关，该复合物既包括组蛋白乙酰基转移酶（TIP60）和组蛋白交换（P400/Domino）活动。在这里，我们介绍了研究NUA4依赖性乙酰化对H2A.Z型H2A.Z掺入染色质的影响。使用与天然染色质的体外组蛋白交换测定法，我们证明了NUA4先前的染色质乙酰化会极大地刺激H2A的H2A交换。 Z.有趣的是，我们发现NUA4对H2A或H4 N末端尾的乙酰化可以独立刺激SWR1活性。因此，我们证明了H4或H2A N末端赖氨酸残基的突变对H2A具有相似的作用。 Z掺入体内，并且在两个尾巴中携带突变的细胞都是不可生存的。最后，耗竭实验表明，含溴构域的蛋白BDF1对于NUA4依赖性刺激SWR1很重要。这些结果为组蛋白H2A变体的染色质乙酰化和ATP依赖性交换之间的功能串扰提供了重要的机械洞察力。
Structural and functional analyses of nucleosomes containing histone variant H2A.Z have drawn a lot of interest over the past few years. Important work in budding yeast has shown that H2A.Z (Htz1)-containing nucleosomes are specifically located on the promoter regions of genes, creating a specific chromatin structure that is poised for disassembly during transcription activation. The SWR1 complex is responsible for incorporation of Htz1 into nucleosomes through ATP-dependent exchange of canonical H2A-H2B dimers for Htz1-H2B dimers. Interestingly, the yeast SWR1 complex is functionally linked to the NuA4 acetyltransferase complex in vivo. NuA4 and SWR1 are physically associated in higher eukaryotes as they are homologous to the TIP60/p400 complex, which encompasses both histone acetyltransferase (Tip60) and histone exchange (p400/Domino) activities. Here we present work investigating the impact of NuA4-dependent acetylation on SWR1-driven incorporation of H2A.Z into chromatin. Using in vitro histone exchange assays with native chromatin, we demonstrate that prior chromatin acetylation by NuA4 greatly stimulates the exchange of H2A for H2A. Z. Interestingly, we find that acetylation of H2A or H4 N-terminal tails by NuA4 can independently stimulate SWR1 activity. Accordingly, we demonstrate that mutations of H4 or H2A N-terminal lysine residues have similar effects on H2A. Z incorporation in vivo, and cells carrying mutations in both tails are nonviable. Finally, depletion experiments indicate that the bromodomain-containing protein Bdf1 is important for NuA4-dependent stimulation of SWR1. These results provide important mechanistic insight into the functional cross-talk between chromatin acetylation and ATP-dependent exchange of histone H2A variants.