Silencing near tRNA genes is nucleosome-mediated and distinct from boundary element function
Silencing near tRNA genes is nucleosome-mediated and distinct from boundary element function
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DOI：
10.1016/j.gene.2013.05.016
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发表时间：
2013-08-15
期刊：
影响因子：
3.5
通讯作者：
Engelke, David R.
中科院分区：
文献类型：
--
作者：
Good, Paul D.;Kendall, Ann;Engelke, David R.
转移RNA （tRNA）基因和其他RNA聚合酶III转录单位在整个核基因组中以高拷贝分布，并且可以在其直接染色体位点上拮抗RNA聚合酶II转录。先前对酿酒酵母的研究发现，这种局部沉默需要tRNA基因在核仁附近的亚核聚类。在这里，我们表明沉默也需要核小体的参与，尽管核小体相互作用的性质似乎不同于其他形式的转录沉默。对广泛的组蛋白氨基酸取代文库的分析发现，在组蛋白n端尾部和核小体盘表面都有大量影响沉默的残基。所涉及的圆盘表面上的残留物与影响其他调节现象的残留物在很大程度上是不同的。与影响tgm沉默的大量组蛋白残基一致，对染色质修饰突变的调查表明，还需要几种已知影响核小体修饰和定位的酶。这些酶包括Rpd3去乙酰化酶复合物、Hos1去乙酰化酶、Glc7磷酸酶和RSC核小体重塑活性，但不包括其他沉默形式或tRNA基因位点边界元件功能所需的多种其他活性。讨论了tRNA基因转录复合物与局部染色质之间的通讯模式。(C) 2013 Elsevier B.V.版权所有
Transfer RNA (tRNA) genes and other RNA polymerase III transcription units are dispersed in high copy throughout nuclear genomes, and can antagonize RNA polymerase II transcription in their immediate chromosomal locus. Previous work in Saccharomyces cerevisiae found that this local silencing required subnuclear clustering of the tRNA genes near the nucleolus. Here we show that the silencing also requires nucleosome participation, though the nature of the nucleosome interaction appears distinct from other forms of transcriptional silencing. Analysis of an extensive library of histone amino acid substitutions finds a large number of residues that affect the silencing, both in the histone N-terminal tails and on the nucleosome disk surface. The residues on the disk surfaces involved are largely distinct from those affecting other regulatory phenomena. Consistent with the large number of histone residues affecting tgm silencing, survey of chromatin modification mutations shows that several enzymes known to affect nucleosome modification and positioning are also required. The enzymes include an Rpd3 deacetylase complex, Hos1 deacetylase, Glc7 phosphatase, and the RSC nucleosome remodeling activity, but not multiple other activities required for other silencing forms or boundary element function at tRNA gene loci. Models for communication between the tRNA gene transcription complexes and local chromatin are discussed. (C) 2013 Elsevier B.V. All rights reserved.