Genome instability and transcription elongation impairment in human cells depleted of THO/TREX.
Genome instability and transcription elongation impairment in human cells depleted of THO/TREX.
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DOI：
10.1371/journal.pgen.1002386
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发表时间：
2011-12
期刊：
影响因子：
4.5
通讯作者：
Aguilera A
中科院分区：
文献类型：
--
作者：
Domínguez-Sánchez MS;Barroso S;Gómez-González B;Luna R;Aguilera A
在酵母中，THO/TREX将转录与基因组完整性联系起来，但哺乳动物THO在这些过程中的作用尚不确定，这表明mRNP生物发生因子在酵母和人类基因组完整性中的差异含义。研究表明，人类THO消耗会损害转录延伸和mRNA输出，并增加与DNA断裂相关的不稳定性，导致超重组和γH2AX和53BP1病灶积累。这伴随着DNA梳理确定的复制改变。基因组的不稳定性是r环依赖的，这可以从AID酶增加DNA损伤的能力和RNaseH减少DNA损伤的能力推断出来，也可以从CH12小鼠细胞中thoc1耗竭引起的r环依赖的类别转换增强推断出来。因此，哺乳动物THO阻止R-loop的形成，并在基因组动力学和功能中发挥作用，这与这些mRNP生物发生因子与基因组完整性之间功能联系的进化守恒一致，这是之前没有预料到的。THO/TREX是一种真核生物保守复合体，首次在出芽酵母中发现，它在转录和mRNP（核糖核蛋白）输出之间起作用。在酵母中，THO突变体表现出基因表达缺陷和转录相关的重组表型。尽管THO/TREX具有结构上的保守性，但目前尚不清楚其在哺乳动物中的功能相关性是否相同，其中有几篇报道已经确定了THO/TREX与转录分离的作用。我们已经询问了哺乳动物THO/TREX功能是否与转录有关，以及这种功能是否需要防止r环形成和维持基因组完整性。我们的研究表明，人类THO亚基，特别是THOC1/hHPR1的消耗，会降低转录延伸，影响mRNA输出，并增加与DNA断裂积累相关的基因组不稳定性。这种基因组不稳定性是依赖于r环的，并伴随着全球复制模式的改变和重组的增加。我们得出的结论是，人类THO/TREX阻止了可能损害基因组完整性的r环的形成。因此，这项工作为mRNP生物发生因子和R环在人类基因组完整性中的作用提供了实验证据。
THO/TREX connects transcription with genome integrity in yeast, but a role of mammalian THO in these processes is uncertain, which suggests a differential implication of mRNP biogenesis factors in genome integrity in yeast and humans. We show that human THO depletion impairs transcription elongation and mRNA export and increases instability associated with DNA breaks, leading to hyper-recombination and γH2AX and 53BP1 foci accumulation. This is accompanied by replication alteration as determined by DNA combing. Genome instability is R-loop–dependent, as deduced from the ability of the AID enzyme to increase DNA damage and of RNaseH to reduce it, or from the enhancement of R-loop–dependent class-switching caused by THOC1-depletion in CH12 murine cells. Therefore, mammalian THO prevents R-loop formation and has a role in genome dynamics and function consistent with an evolutionary conservation of the functional connection between these mRNP biogenesis factors and genome integrity that had not been anticipated. THO/TREX is an eukaryotic conserved complex, first identified in budding yeast, that acts at the interface between transcription and mRNP (ribonucleoprotein) export. In yeast, THO mutants show gene expression defects and a transcription-associated recombination phenotype. Despite the structural conservation of THO/TREX, it is unclear whether the functional relevance is the same in mammals, in which several reports have identified a role of THO/TREX separated from transcription. We have asked whether mammalian THO/TREX function is connected to transcription and whether this function is required to prevent R-loop formation and to maintain genome integrity. Our study reveals that depletion of human THO subunits, in particular THOC1/hHPR1, reduces transcription elongation, affects mRNA export, and increases genome instability associated with the accumulation of DNA breaks. This genome instability is R-loop–dependent and is accompanied by an alteration of global replication patterns and an increase in recombination. We conclude that human THO/TREX prevents the formation of R-loops that can compromise genome integrity. This work, therefore, provides experimental evidence for a role of mRNP biogenesis factors and R loops in genome integrity in humans.
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