Abstract：
Assembly of TopBP1 biomolecular condensates triggers activation of the ataxia telangiectasia-mutated and Rad3-related (ATR)/Chk1 signaling pathway, which coordinates cell responses to impaired DNA replication. Here, we used optogenetics and reverse genetics to investigate the role of sequence-specific motifs in the formation and functions of TopBP1 condensates. We propose that BACH1/FANCJ is involved in the partitioning of BRCA1 within TopBP1 compartments. We show that Chk1 is activated at the interface of TopBP1 condensates and provide evidence that these structures arise at sites of DNA damage and in primary human fibroblasts. Chk1 phosphorylation depends on the integrity of a conserved arginine motif within TopBP1\'s ATR activation domain (AAD). Its mutation uncouples Chk1 activation from TopBP1 condensation, revealing that optogenetically induced Chk1 phosphorylation triggers cell cycle checkpoints and slows down replication forks in the absence of DNA damage. Together with previous work, these data suggest that the intrinsically disordered AAD encodes distinct molecular steps in the ATR/Chk1 pathway.
摘要：
TopBP1生物分子缩合物的组装触发了共济失调毛细血管扩张突变和Rad3相关（ATR）/Chk1信号通路的激活，协调细胞对受损DNA复制的反应。这里,我们使用光遗传学和反向遗传学研究了序列特异性基序在TopBP1缩合物形成和功能中的作用.我们建议BACH1/FANCJ参与BRCA1在TopBP1区室中的分配。我们显示Chk1在TopBP1缩合物的界面处被激活，并提供了这些结构出现在DNA损伤位点和原代人成纤维细胞中的证据。Chk1磷酸化取决于TopBP1的ATR激活域(AAD)内保守精氨酸基序的完整性。它的突变使Chk1激活与TopBP1缩合分离，揭示光遗传学诱导的Chk1磷酸化触发细胞周期检查点，并在没有DNA损伤的情况下减慢复制叉。加上以前的工作，这些数据表明，内在无序的AAD在ATR/Chk1通路中编码不同的分子步骤。
