RAD51 paralogs synergize with RAD51 to protect reversed forks from cellular nucleases

Chia Lun Guh, Kai Hang Lei, Yi An Chen, Yi Zhen Jiang, Hao Yen Chang, Hungjiun Liaw, Hung Wen Li, Hsin Yung Yen, Peter Chi

Research output: Contribution to journalArticlepeer-review


Fork reversal is a conserved mechanism to prevent stalled replication forks from collapsing. Formation and protection of reversed forks are two crucial steps in ensuring fork integrity and stability. Five RAD51 paralogs, namely, RAD51B, RAD51C, RAD51D, XRCC2 and XRCC3, which share sequence and structural similarity to the recombinase RAD51, play poorly defined mechanistic roles in these processes. Here, using purified BCDX2 (RAD51BCD-XRCC2) and CX3 (RAD51C-XRCC3) complexes and in vitro reconstituted biochemical systems, we mechanistically dissect their functions in forming and protecting reversed forks. We show that both RAD51 paralog complexes lack fork reversal activities. Whereas CX3 exhibits modest fork protection activity, BCDX2 significantly synergizes with RAD51 to protect DNA against attack by the nucleases MRE11 and EXO1. DNA protection is contingent upon the ability of RAD51 to form a functional nucleoprotein filament on DNA. Collectively, our results provide evidence for a hitherto unknown function of RAD51 paralogs in synergizing with RAD51 nucleoprotein filament to prevent degradation of stressed replication forks.

Original languageEnglish
Pages (from-to)11717-11731
Number of pages15
JournalNucleic acids research
Issue number21
Publication statusPublished - 2023 Nov 27

All Science Journal Classification (ASJC) codes

  • Genetics


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