Abstract
Replication stress from stalled or collapsed replication forks is a major challenge to genomic integrity. The anticancer agent camptothecin (CPT) is a DNA topoisomerase I inhibitor that causes fork collapse and double-strand breaks amid DNA replication. Here we report that hMSH5 promotes cell survival in response to CPT-induced DNA damage. Cells deficient in hMSH5 show elevated CPT-induced γ-H2AX and RPA2 foci with concomitant reduction of Rad51 foci, indicative of impaired homologous recombination. In addition, CPT-treated hMSH5-deficient cells exhibit aberrant activation of Chk1 and Chk2 kinases and therefore abnormal cell cycle progression. Furthermore, the hMSH5-FANCJ chromatin recruitment underlies the effects of hMSH5 on homologous recombination and Chk1 activation. Intriguingly, FANCJ depletion desensitizes hMSH5-deficient cells to CPT-elicited cell killing. Collectively, our data point to the existence of a functional interplay between hMSH5 and FANCJ in double-strand break repair induced by replication stress.
Highlights
Our data point to the existence of a functional interplay between hMSH5 and FANCJ in double-strand break repair induced by replication stress
FANCJ is implicated to function in the processes of homologous recombination (HR), DNA damage signaling, and DNA replication (26 –30)
We found that hMSH5 facilitated the chromatin loading of Rad51 to promote HR in CPT-induced double-strand breaks (DSBs) repair
Summary
Single-strand breaks created by CPT could be converted into double-strand breaks (DSBs) during DNA replication The repair of these so-called replication-associated DSBs or one-ended DSBs is orchestrated by the actions of DNA damage response and repair pathways [4]. The resulting HR intermediate structures can be channeled into one of the downstream processes such as double-Holliday junction repair, synthesis-dependent strand annealing, sister chromatid exchange, or break-induced replication [8, 9]. In due course, these pathways help to maintain genomic stability, of which double-Holliday junction repair is conceived as the main process for rescuing collapsed DNA replication forks. We demonstrate that hMSH5 directly interacts with FANCJ, and the resulting complex promotes HR and facilitates the ATR-Chk signaling in response to CPT
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