Wei Leizhen, Nakajima Satoshi, Böhm Stefanie, Bernstein Kara A, Shen Zhiyuan, Tsang Michael, Levine Arthur S, Lan Li
University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219;
Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903;
Proc Natl Acad Sci U S A. 2015 Jul 7;112(27):E3495-504. doi: 10.1073/pnas.1507105112. Epub 2015 Jun 22.
Damage repair mechanisms at transcriptionally active sites during the G0/G1 phase are largely unknown. To elucidate these mechanisms, we introduced genome site-specific oxidative DNA damage and determined the role of transcription in repair factor assembly. We find that KU and NBS1 are recruited to damage sites independent of transcription. However, assembly of RPA1, RAD51C, RAD51, and RAD52 at such sites is strictly governed by active transcription and requires both wild-type Cockayne syndrome protein B (CSB) function and the presence of RNA in the G0/G1 phase. We show that the ATPase activity of CSB is indispensable for loading and binding of the recombination factors. CSB counters radiation-induced DNA damage in both cells and zebrafish models. Taken together, our results have uncovered a novel, RNA-based recombination mechanism by which CSB protects genome stability from strand breaks at transcriptionally active sites and may provide insight into the clinical manifestations of Cockayne syndrome.
G0/G1期转录活跃位点的损伤修复机制在很大程度上尚不清楚。为了阐明这些机制，我们引入了基因组位点特异性氧化DNA损伤，并确定了转录在修复因子组装中的作用。我们发现KU和NBS1被招募到损伤位点，与转录无关。然而，RPA1、RAD51C、RAD51和RAD52在此类位点的组装严格受活跃转录的调控，并且在G0/G1期需要野生型科凯恩综合征蛋白B（CSB）的功能以及RNA的存在。我们表明，CSB的ATP酶活性对于重组因子的加载和结合是不可或缺的。CSB在细胞和斑马鱼模型中都能对抗辐射诱导的DNA损伤。综上所述，我们的研究结果揭示了一种新的基于RNA的重组机制，通过该机制CSB保护基因组稳定性免受转录活跃位点的链断裂影响，并可能为科凯恩综合征的临床表现提供见解。
