A critical epitope for substrate recognition by the nucleosome remodeling ATPase ISWI
A critical epitope for substrate recognition by the nucleosome remodeling ATPase ISWI
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DOI：
10.1093/nar/30.3.649
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发表时间：
2002-02-01
影响因子：
14.9
通讯作者：
Becker, PB
中科院分区：
文献类型：
--
作者：
Clapier, CR;Nightingale, KP;Becker, PB
atp酶ISWI是几个核小体重塑复合体的催化核心，它能够改变核小体内组蛋白与DNA的相互作用，从而促进组蛋白八聚体在DNA上的滑动。动态核小体重定位可能涉及染色质与规则间隔的核小体和可接近的调控序列元件的组装。核小体滑动背后的机制在很大程度上尚未解决。我们最近发现组蛋白H4的n端“尾巴”对ISWI的核小体重塑至关重要。如果删除，核小体不再被识别为底物，也不会刺激ISWI的atp酶活性。我们在这里表明，H4尾部是一个更复杂的识别表位的一部分，通过将H4 n端嫁接到其他组蛋白上而被破坏。我们将H4尾巴的需求映射到由位于尾巴基部的氨基酸R17H18R19组成的亲水斑块。这些残基先前已被证明与核小体DNA接触，表明ISWI识别由DNA结合的H4尾部组成的“表位”。与这一假设相一致的是，只有在DNA存在的情况下，分离的H4尾肽才会刺激ISWI atp酶。相邻K（12）和K（16）残基的乙酰化削弱了ISWI对底物的识别。
The ATPase ISWI is the catalytic core of several nucleosome remodeling complexes, which are able to alter histone-DNA interactions within nucleosomes such that the sliding of histone octamers on DNA is facilitated. Dynamic nucleosome repositioning may be involved in the assembly of chromatin with regularly spaced nucleosomes and accessible regulatory sequence elements. The mechanism that underlies nucleosome sliding is largely unresolved. We recently discovered that the N-terminal 'tail' of histone H4 is critical for nucleosome remodeling by ISWI. If deleted, nucleosomes are no longer recognized as substrates and do not stimulate the ATPase activity of ISWI. We show here that the H4 tail is part of a more complex recognition epitope which is destroyed by grafting the H4 N-terminus onto other histones. We mapped the H4 tail requirement to a hydrophilic patch consisting of the amino acids R17H18R19 localized at the base of the tail. These residues have been shown earlier to contact nucleosomal DNA, suggesting that ISWI recognizes an 'epitope' consisting of the DNA-bound H4 tail. Consistent with this hypothesis, the ISWI ATPase is stimulated by isolated H4 tail peptides ISWI only in the presence of DNA. Acetylation of the adjacent K(12)andK(16) residues impairs substrate recognition by ISWI.