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Abstract：
Homologous-recombination deficiency due to breast cancer 1/2 (BRCA1/2) mutations or mimicking BRCA1/2 mutations confer synthetic lethality with poly-(ADP)-ribose polymerase 1/2 inhibitors. The chromatin regulator Pax2 transactivation domain interacting protein (PTIP) promotes stalled replication fork degradation in BRCA1-deficient cells, but the underlying mechanism by which PTIP regulates stalled replication fork stability is unclear. Here, we performed a series of in vitro analyses to dissect the function of UFMylation in regulating fork stabilization in BRCA1-deficient cells. By denaturing co-immunoprecipitation, we first found that replication stress can induce PTIP UFMylation. Interestingly, this post-translational modification promotes end resection and degradation of nascent DNA at stalled replication forks in BRCA1-deficient cells. By cell viability assay, we found that PTIP-depleted and UFL1-depleted BRCA1 knockdown cells are less sensitive to poly-(ADP)-ribose polymerase inhibitors than the siRNA targeting negative control BRCA1-deficient cells. These results identify a new mechanism by which PTIP UFMylation confers chemoresistance in BRCA1-deficient cells.
摘要：
“BRCAness”定义了由于BRCA1或BRCA2突变而导致同源重组（HR）缺陷的癌症。这些突变赋予PARP1/2抑制剂的合成致死性。染色质调节剂PTIP促进“BRCAness”细胞中停滞的复制叉降解，但是PTIP调节停滞复制叉稳定性的潜在机制尚不清楚。这里,我们进行了一系列体外分析，以剖析UFMylation在BRCA1缺陷细胞中调节叉稳定的功能。通过变性免疫共沉淀，我们首先发现复制胁迫可以诱导PTIPUFM1化。有趣的是,这种翻译后修饰促进了BRCA1缺陷细胞中停滞复制叉处新生DNA的末端切除和降解.通过细胞活力测定，我们发现,与靶向siRNA的阴性对照BRCA1缺陷细胞相比,PTIP缺失和UFL1缺失的BRCA1敲低细胞对PARP抑制剂的敏感性较低.这些结果确定了一种新的机制，通过该机制，PTIPUFM化赋予BRCA1缺陷型细胞的化学抗性。
