Deparment of Molecular Biology and Genetics, Cornell University Ithaca, Ithaca, New York, United States of America.
Department of Biology, University of Copenhagen, Copenhagen N, Denmark.
PLoS Genet. 2022 Sep 13;18(9):e1010412. doi: 10.1371/journal.pgen.1010412. eCollection 2022 Sep.
Homologous recombination (HR) is a double-strand break DNA repair pathway that preserves chromosome structure. To repair damaged DNA, HR uses an intact donor DNA sequence located elsewhere in the genome. After the double-strand break is repaired, DNA sequence information can be transferred between donor and recipient DNA molecules through different mechanisms, including DNA crossovers that form between homologous chromosomes. Regulation of DNA sequence transfer is an important step in effectively completing HR and maintaining genome integrity. For example, mitotic exchange of information between homologous chromosomes can result in loss-of-heterozygosity (LOH), and in higher eukaryotes, the development of cancer. The DNA motor protein Rdh54 is a highly conserved DNA translocase that functions during HR. Several existing phenotypes in rdh54Δ strains suggest that Rdh54 may regulate effective exchange of DNA during HR. In our current study, we used a combination of biochemical and genetic techniques to dissect the role of Rdh54 on the exchange of genetic information during DNA repair. Our data indicate that RDH54 regulates DNA strand exchange by stabilizing Rad51 at an early HR intermediate called the displacement loop (D-loop). Rdh54 acts in opposition to Rad51 removal by the DNA motor protein Rad54. Furthermore, we find that expression of a catalytically inactivate allele of Rdh54, rdh54K318R, favors non-crossover outcomes. From these results, we propose a model for how Rdh54 may kinetically regulate strand exchange during homologous recombination.
同源重组（HR）是一种双链断裂 DNA 修复途径，可维持染色体结构。为了修复受损的 DNA，HR 使用位于基因组其他位置的完整供体 DNA 序列。双链断裂修复后，供体和受体 DNA 分子之间可以通过不同的机制转移 DNA 序列信息，包括在同源染色体之间形成的 DNA 交叉。DNA 序列转移的调控是有效完成 HR 和维持基因组完整性的重要步骤。例如，有丝分裂过程中同源染色体之间信息的交换会导致杂合性丢失（LOH），在高等真核生物中，会导致癌症的发生。Rdh54 是一种高度保守的 DNA 转位酶，在 HR 过程中发挥作用。在 rdh54Δ 菌株中存在几种现有表型，表明 Rdh54 可能调节 HR 过程中 DNA 有效交换。在我们目前的研究中，我们使用生化和遗传技术的组合来剖析 Rdh54 在 DNA 修复过程中遗传信息交换中的作用。我们的数据表明，RDH54 通过稳定早期 HR 中间体（称为置换环（D-loop））中的 Rad51 来调节 DNA 链交换。Rdh54 作用于 Rad54 去除 Rad51，Rad54 是一种 DNA 马达蛋白。此外，我们发现表达 Rdh54 的催化失活等位基因 rdh54K318R 有利于非交叉结果。根据这些结果，我们提出了 Rdh54 如何在同源重组过程中动态调节链交换的模型。
