The histone chaperone Asf1 increases the rate of histone eviction at the yeast PHO5 and PHO8 promoters
The histone chaperone Asf1 increases the rate of histone eviction at the yeast PHO5 and PHO8 promoters
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DOI：
10.1074/jbc.m513340200
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发表时间：
2006-03-03
影响因子：
4.8
通讯作者：
Hörz, W
中科院分区：
文献类型：
--
作者：
Korber, P;Barbaric, S;Hörz, W
真核基因表达从一个很大程度上阻塞的染色质底物开始，该底物必须通过染色质重塑的调节机制来提供。酵母PHO 5启动子是基因诱导过程中定位的核小体对基因阻遏和广泛的染色质重塑的贡献的众所周知的例子。最近，这一重塑过程的机制被证明是导致解体的启动子核小体和驱逐的组成组蛋白的反式。这一发现要求在反式组蛋白受体，从而使组蛋白伴侣可能参与这一过程。在这项研究中，我们已经表明，组蛋白伴侣Asf 1增加组蛋白驱逐率在PHO 5启动子。在没有Asf 1的情况下，组蛋白驱逐被延迟，但染色质转变的最终结果不受影响。对于共调节的PHO 8启动子也是如此，其中诱导也导致组蛋白驱逐，并且在asf 1菌株中组蛋白丢失的速率也降低，尽管不太严重。重要的是，染色质重塑的最终程度不受影响。我们还提供了证据表明Asf 1和SWI/SNF染色质重塑复合物在不同的平行但功能重叠的途径中工作，即它们都有助于相同的结果，而不是相互严格依赖。
Eukaryotic gene expression starts off from a largely obstructive chromatin substrate that has to be rendered accessible by regulated mechanisms of chromatin remodeling. The yeast PHO5 promoter is a well known example for the contribution of positioned nucleosomes to gene repression and for extensive chromatin remodeling in the course of gene induction. Recently, the mechanism of this remodeling process was shown to lead to the disassembly of promoter nucleosomes and the eviction of the constituent histones in trans. This finding called for a histone acceptor in trans and thus made histone chaperones likely to be involved in this process. In this study we have shown that the histone chaperone Asf1 increases the rate of histone eviction at the PHO5 promoter. In the absence of Asf1 histone eviction is delayed, but the final outcome of the chromatin transition is not affected. The same is true for the coregulated PHO8 promoter where induction also leads to histone eviction and where the rate of histone loss is reduced in asf1 strains as well, although less severely. Importantly, the final extent of chromatin remodeling is not affected. We have also presented evidence that Asf1 and the SWI/SNF chromatin remodeling complex work in distinct parallel but functionally overlapping pathways, i.e. they both contribute toward the same outcome without being mutually strictly dependent.