Institut Génétique Reproduction et Développement (iGReD), Université Clermont Auvergne, UMR 6293 CNRS, U1103 INSERM, Clermont-Ferrand, France.
PLoS Genet. 2022 Aug 25;18(8):e1010322. doi: 10.1371/journal.pgen.1010322. eCollection 2022 Aug.
Ensuring balanced distribution of chromosomes in gametes, meiotic recombination is essential for fertility in most sexually reproducing organisms. The repair of the programmed DNA double strand breaks that initiate meiotic recombination requires two DNA strand-exchange proteins, RAD51 and DMC1, to search for and invade an intact DNA molecule on the homologous chromosome. DMC1 is meiosis-specific, while RAD51 is essential for both mitotic and meiotic homologous recombination. DMC1 is the main catalytically active strand-exchange protein during meiosis, while this activity of RAD51 is downregulated. RAD51 is however an essential cofactor in meiosis, supporting the function of DMC1. This work presents a study of the mechanism(s) involved in this and our results point to DMC1 being, at least, a major actor in the meiotic suppression of the RAD51 strand-exchange activity in plants. Ectopic expression of DMC1 in somatic cells renders plants hypersensitive to DNA damage and specifically impairs RAD51-dependent homologous recombination. DNA damage-induced RAD51 focus formation in somatic cells is not however suppressed by ectopic expression of DMC1. Interestingly, DMC1 also forms damage-induced foci in these cells and we further show that the ability of DMC1 to prevent RAD51-mediated recombination is associated with local assembly of DMC1 at DNA breaks. In support of our hypothesis, expression of a dominant negative DMC1 protein in meiosis impairs RAD51-mediated DSB repair. We propose that DMC1 acts to prevent RAD51-mediated recombination in Arabidopsis and that this down-regulation requires local assembly of DMC1 nucleofilaments.
确保染色体在配子中的平衡分布，减数分裂重组对于大多数有性繁殖生物的生育能力至关重要。启动减数分裂重组的程序性 DNA 双链断裂的修复需要两种 DNA 链交换蛋白 RAD51 和 DMC1，以在同源染色体上搜索并入侵完整的 DNA 分子。DMC1 是减数分裂特异性的，而 RAD51 对于有丝分裂和减数分裂同源重组都是必不可少的。DMC1 是减数分裂中主要的催化活性链交换蛋白，而 RAD51 的这种活性被下调。然而，RAD51 是减数分裂中的一个重要协同因子，支持 DMC1 的功能。这项工作研究了涉及到的机制，我们的结果表明，DMC1 至少是植物中减数分裂抑制 RAD51 链交换活性的主要因素。在体细胞中异位表达 DMC1 会使植物对 DNA 损伤敏感，并特异性损害 RAD51 依赖的同源重组。然而，体细胞中 RAD51 依赖的同源重组并不受 DMC1 异位表达的抑制。有趣的是，DMC1 也在这些细胞中形成损伤诱导的焦点，我们进一步表明，DMC1 防止 RAD51 介导的重组的能力与 DMC1 在 DNA 断裂处的局部组装有关。支持我们的假设，在减数分裂中表达显性负性 DMC1 蛋白会损害 RAD51 介导的 DSB 修复。我们提出，DMC1 在拟南芥中作用是防止 RAD51 介导的重组，这种下调需要 DMC1 核丝的局部组装。
