Department of Genetics, Harvard University Medical School, Boston, MA 02115, USA.
Mol Cell. 2012 Aug 10;47(3):396-409. doi: 10.1016/j.molcel.2012.05.024. Epub 2012 Jun 14.
Completion of DNA replication after replication stress depends on PCNA, which undergoes monoubiquitination to stimulate direct bypass of DNA lesions by specialized DNA polymerases or is polyubiquitinated to promote recombination-dependent DNA synthesis across DNA lesions by template switching mechanisms. Here we report that the ZRANB3 translocase, a SNF2 family member related to the SIOD disorder SMARCAL1 protein, is recruited by polyubiquitinated PCNA to promote fork restart following replication arrest. ZRANB3 depletion in mammalian cells results in an increased frequency of sister chromatid exchange and DNA damage sensitivity after treatment with agents that cause replication stress. Using in vitro biochemical assays, we show that recombinant ZRANB3 remodels DNA structures mimicking stalled replication forks and disassembles recombination intermediates. We therefore propose that ZRANB3 maintains genomic stability at stalled or collapsed replication forks by facilitating fork restart and limiting inappropriate recombination that could occur during template switching events.
复制压力后 DNA 复制的完成依赖于 PCNA，PCNA 发生单泛素化可刺激专门的 DNA 聚合酶直接绕过 DNA 损伤，或发生多泛素化以通过模板转换机制促进跨越 DNA 损伤的重组依赖性 DNA 合成。在这里，我们报告说，ZRANB3 转位酶是 SNF2 家族的成员，与 SIOD 疾病 SMARCAL1 蛋白有关，它被多泛素化的 PCNA 募集来促进复制停滞后的叉重新启动。哺乳动物细胞中 ZRANB3 的缺失会导致在用引起复制压力的试剂处理后姐妹染色单体交换和 DNA 损伤敏感性增加。通过体外生化测定，我们表明重组 ZRANB3 重塑了模拟停滞复制叉的 DNA 结构，并解离了重组中间体。因此，我们提出 ZRANB3 通过促进叉重新启动并限制模板转换事件中可能发生的不合适重组，来维持停滞或崩溃的复制叉处的基因组稳定性。
