Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen N, Denmark.
Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen N, Denmark.
Mol Cell. 2016 Dec 15;64(6):1117-1126. doi: 10.1016/j.molcel.2016.10.037.
Homologous recombination (HR) is necessary to counteract DNA replication stress. Common fragile site (CFS) loci are particularly sensitive to replication stress and undergo pathological rearrangements in tumors. At these loci, replication stress frequently activates DNA repair synthesis in mitosis. This mitotic DNA synthesis, termed MiDAS, requires the MUS81-EME1 endonuclease and a non-catalytic subunit of the Pol-delta complex, POLD3. Here, we examine the contribution of HR factors in promoting MiDAS in human cells. We report that RAD51 and BRCA2 are dispensable for MiDAS but are required to counteract replication stress at CFS loci during S-phase. In contrast, MiDAS is RAD52 dependent, and RAD52 is required for the timely recruitment of MUS81 and POLD3 to CFSs in early mitosis. Our results provide further mechanistic insight into MiDAS and define a specific function for human RAD52. Furthermore, selective inhibition of MiDAS may comprise a potential therapeutic strategy to sensitize cancer cells undergoing replicative stress.
同源重组（HR）对于抵消 DNA 复制压力是必要的。常见的脆弱位点（CFS）在肿瘤中对复制压力特别敏感，容易发生病理性重排。在这些位置，复制压力经常在有丝分裂中激活 DNA 修复合成。这种有丝分裂 DNA 合成，称为 MiDAS，需要 MUS81-EME1 内切酶和 Pol-delta 复合物的非催化亚基 POLD3。在这里，我们研究了 HR 因素在促进人细胞 MiDAS 中的作用。我们报告 RAD51 和 BRCA2 对于 MiDAS 不是必需的，但在 S 期对于 CFS 位点的复制压力是必需的。相比之下，MiDAS 依赖 RAD52，并且 RAD52 对于 MUS81 和 POLD3 在早期有丝分裂中及时募集到 CFS 是必需的。我们的结果为 MiDAS 提供了进一步的机制见解，并定义了人类 RAD52 的特定功能。此外，选择性抑制 MiDAS 可能构成一种潜在的治疗策略，以增敏经历复制应激的癌细胞。
