In order to prevent the deleterious effects of genotoxic agents, cells have developed complex surveillance mechanisms and DNA repair pathways that allow them to maintain genome integrity. The ubiquitin-specific protease 9X (USP9X) contributes to genome stability during DNA replication and chromosome segregation. Depletion of USP9X leads to DNA double-strand breaks, some of which are triggered by replication fork collapse. Here, we identify USP9X as a novel regulator of homologous recombination (HR) DNA repair in human cells. By performing cellular HR reporter, irradiation-induced focus formation and colony formation assays, we show that USP9X is required for efficient HR. Mechanistically, we show USP9X is important to sustain the expression levels of key HR factors, namely BRCA1 and RAD51 through a non-canonical regulation of their mRNA abundance. Intriguingly, we find that the contribution of USP9X to BRCA1 and RAD51 expression is independent of its known catalytic activity. Thus, this work identifies USP9X as a regulator of HR, demonstrates a novel mechanism by which USP9X can regulate protein levels, and provides insights in to the regulation of BRCA1 and RAD51 mRNA.This article has an associated First Person interview with the first author of the paper.

中文翻译：

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USP9X 去泛素化酶对同源重组 DNA 修复的非规范调节。

为了防止基因毒剂的有害影响，细胞开发出了复杂的监视机制和 DNA 修复途径，使它们能够维持基因组的完整性。泛素特异性蛋白酶 9X (USP9X) 有助于 DNA 复制和染色体分离过程中基因组的稳定性。USP9X 的耗尽会导致 DNA 双链断裂，其中一些断裂是由复制叉崩溃引发的。在这里，我们将 USP9X 确定为人类细胞中同源重组 (HR) DNA 修复的新型调节剂。通过进行细胞 HR 报告基因、辐射诱导的病灶形成和集落形成测定，我们表明 USP9X 是有效 HR 所必需的。从机制上讲，我们表明 USP9X 通过非规范调节 mRNA 丰度来维持关键 HR 因子（即 BRCA1 和 RAD51）的表达水平非常重要。有趣的是，我们发现 USP9X 对 BRCA1 和 RAD51 表达的贡献与其已知的催化活性无关。因此，这项工作将 USP9X 确定为 HR 的调节剂，展示了 USP9X 调节蛋白质水平的新机制，并提供了有关 BRCA1 和 RAD51 mRNA 调节的见解。本文有与第一作者的相关第一人称采访纸。