Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC, Av. Américo Vespucio s/n, 41092 Sevilla, Spain.
Mol Cell. 2010 Mar 12;37(5):690-701. doi: 10.1016/j.molcel.2010.02.008.
Homologous recombination is a major double-strand break (DSB) repair mechanism that acts during the S and G2 phases. In contrast, nucleotide excision repair (NER) is a major pathway for the repair of DNA bulky adducts that is unrelated to replication. We show that replication can be strongly disturbed in a specific type of rad3/XPD NER mutant of TFIIH, causing replication fork breakage. In contrast to classical NER-deficient mutations, the S. cerevisiae rad3-102 allele, which has a minimal impact on UV resistance, channels bulky adducts into DSBs. rad3-102 allows Rad1/XPF- and Rad2/XPG-catalyzed DNA incisions but fails to perform postincision steps retaining TFIIH at the damaged site. Broken forks are rescued by MRX-Rad52-Rfc1-dependent recombination via two types of replication restart mechanisms, one being Rad51 dependent and the other Pol32 dependent. Our results define the genetic and molecular hallmarks of replication fork breakage and restart and bring insights to understand specific NER-related human syndromes.
同源重组是一种主要的双链断裂 (DSB) 修复机制，发生在 S 和 G2 期。相比之下，核苷酸切除修复 (NER) 是修复与复制无关的 DNA 大体积加合物的主要途径。我们表明，在 TFIIH 的一种特定类型的 rad3/XPD NER 突变体中，复制可以被强烈干扰，导致复制叉断裂。与经典的 NER 缺陷突变不同，酿酒酵母 rad3-102 等位基因对 UV 抗性的影响最小，将大体积加合物导入 DSB。rad3-102 允许 Rad1/XPF 和 Rad2/XPG 催化的 DNA 切口，但无法进行切口后步骤，使 TFIIH 保留在受损部位。通过 MRX-Rad52-Rfc1 依赖性重组，通过两种类型的复制重新启动机制，一种依赖 Rad51，另一种依赖 Pol32，来挽救断裂的叉子。我们的结果定义了复制叉断裂和重新启动的遗传和分子特征，并为理解特定的与 NER 相关的人类综合征提供了见解。
