RNA processing factors Swd2.2 and Sen1 antagonize RNA Pol III-dependent transcription and the localization of condensin at Pol III genes.
RNA processing factors Swd2.2 and Sen1 antagonize RNA Pol III-dependent transcription and the localization of condensin at Pol III genes.
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DOI：
10.1371/journal.pgen.1004794
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发表时间：
2014-11
期刊：
影响因子：
4.5
通讯作者：
Vanoosthuyse V
中科院分区：
文献类型：
--
作者：
Legros P;Malapert A;Niinuma S;Bernard P;Vanoosthuyse V
凝聚蛋白介导的染色体凝聚对于细胞分裂时的基因组稳定性是必不可少的。遗传学研究表明，凝聚素与染色质的关联与基因转录密切相关，但与转录相关的特征指导凝聚素的积累仍不清楚。在这里，我们表明，在分裂酵母中，凝聚素成为显着丰富的RNA聚合酶III转录基因时，Swd2.2和Sen 1，两个因子参与转录过程中，同时删除。Sen 1是一种ATP依赖性解旋酶，其在酿酒酵母中的直向同源物有助于终止一些RNA Pol II转录物的转录并拮抗基因组中DNA：RNA杂合体的形成。使用两个独立的映射技术，我们表明，DNA：RNA杂交形式丰富的聚合酶III转录基因在裂变酵母，但我们证明，他们不太可能促进凝聚素的招聘。相反，我们表明，Sen 1与RNA Pol III形成了一个稳定和丰富的复合物，Swd2.2和Sen 1拮抗RNA Pol III与染色质和RNA Pol III依赖性转录的相互作用。当Swd2.2和Sen 1缺乏时，Pol III转录基因的RNA Pol III和缩合素的浓度增加伴随着拓扑异构酶I和II的积累以及局部核小体的消耗，这表明Pol III转录基因遭受拓扑压力。我们提供的证据表明，这种拓扑应力有助于招聘和/或稳定凝聚素在Pol III转录的基因在Swd2.2和Sen 1的情况下。我们的数据挑战的想法，一个进行性RNA聚合酶阻碍了凝聚素的结合，并建议转录相关的拓扑应力可能在某些情况下促进凝聚素的协会。在分裂后期开始之前不能浓缩染色体会导致基因组不稳定。进化保守的凝聚素复合体驱动染色体凝聚，可能是通过改变其结合位点周围染色质的拓扑结构。凝聚蛋白定位于高转录区域，表明一些转录相关特征指导其与染色质的关联。在这里，我们认为转录依赖的DNA：RNA杂合体或拓扑应力可能参与募集凝聚素。我们的数据表明，凝聚素确实是丰富的区域积累DNA：RNA杂交体，但他们不参与其招聘。相反，我们确定了一个突变体的组合，其中RNA聚合酶III的转录增加与局部更强的拓扑应力。引人注目的是，本地化的凝聚素显着增强在同一个位点，我们表明，拓扑应力有助于这种增强的协会。我们的数据加强了这样一种观点，即转录创造了在有丝分裂中招募凝聚素所必需的环境。
Condensin-mediated chromosome condensation is essential for genome stability upon cell division. Genetic studies have indicated that the association of condensin with chromatin is intimately linked to gene transcription, but what transcription-associated feature(s) direct(s) the accumulation of condensin remains unclear. Here we show in fission yeast that condensin becomes strikingly enriched at RNA Pol III-transcribed genes when Swd2.2 and Sen1, two factors involved in the transcription process, are simultaneously deleted. Sen1 is an ATP-dependent helicase whose orthologue in Saccharomyces cerevisiae contributes both to terminate transcription of some RNA Pol II transcripts and to antagonize the formation of DNA:RNA hybrids in the genome. Using two independent mapping techniques, we show that DNA:RNA hybrids form in abundance at Pol III-transcribed genes in fission yeast but we demonstrate that they are unlikely to faciliate the recruitment of condensin. Instead, we show that Sen1 forms a stable and abundant complex with RNA Pol III and that Swd2.2 and Sen1 antagonize both the interaction of RNA Pol III with chromatin and RNA Pol III-dependent transcription. When Swd2.2 and Sen1 are lacking, the increased concentration of RNA Pol III and condensin at Pol III-transcribed genes is accompanied by the accumulation of topoisomerase I and II and by local nucleosome depletion, suggesting that Pol III-transcribed genes suffer topological stress. We provide evidence that this topological stress contributes to recruit and/or stabilize condensin at Pol III-transcribed genes in the absence of Swd2.2 and Sen1. Our data challenge the idea that a processive RNA polymerase hinders the binding of condensin and suggest that transcription-associated topological stress could in some circumstances facilitate the association of condensin. Failure to condense chromosomes prior to anaphase onset can lead to genome instability. The evolutionary-conserved condensin complex drives chromosome condensation, probably by changing the topology of chromatin around its binding sites. Condensin localizes to regions of high transcription, suggesting that some transcription-associated feature(s) direct its association with chromatin. Here we considered that transcription-dependent DNA:RNA hybrids or topological stress could be involved in recruiting condensin. Our data show that condensin is indeed enriched at regions accumulating DNA:RNA hybrids but that they are not involved in its recruitment. Rather, we identify a mutant combination where increased transcription by RNA Pol III is associated locally with stronger topological stress. Strikingly the localization of condensin is dramatically enhanced at the same loci and we show that topological stress contributes to this enhanced association. Our data strengthen the idea that transcription creates the environment necessary to recruit condensin in mitosis.