Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892.
Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892
G3 (Bethesda). 2019 May 7;9(5):1647-1654. doi: 10.1534/g3.119.400150.
In , the meiosis-specific axis proteins Hop1 and Red1 are present nonuniformly across the genome. In a previous study, the meiosis-specific VMA1-derived endonuclease (VDE) was used to examine Spo11-independent recombination in a recombination reporter inserted in a Hop1/Red1-enriched region () and in a Hop1/Red1-poor region (). VDE-initiated crossovers at 4 were mostly dependent on Mlh3, a component of the MutLγ meiotic recombination intermediate resolvase, while VDE-initiated crossovers at were mostly Mlh3-independent. These differences were abolished in the absence of the chromosome axis remodeler Pch2, and crossovers at both loci became partly Mlh3-dependent. To test the generality of these observations, we examined inserts at six additional loci that differed in terms of Hop1/Red1 enrichment, chromosome size, and distance from centromeres and telomeres. All six loci behaved similarly to : the vast majority of VDE-initiated crossovers were Mlh3-independent. This indicates that, counter to previous suggestions, levels of meiotic chromosome axis protein enrichment alone do not determine which recombination pathway gives rise to crossovers during VDE-initiated meiotic recombination. In mutants, the fraction of VDE-induced crossovers that were Mlh3-dependent increased to levels previously observed for Spo11-initiated crossovers in , indicating that Pch2-dependent processes play an important role in controlling the balance between MutLγ-dependent and MutLγ-independent crossovers.
在 中，减数分裂特异性轴蛋白 Hop1 和 Red1 在整个基因组中不均匀存在。在之前的研究中，使用减数分裂特异性的 VMA1 衍生内切酶 (VDE) 检查了插入 Hop1/Red1 富集区（）和 Hop1/Red1 贫化区（）中的重组报告器中的 Spo11 非依赖性重组。在 4 处的 VDE 引发的交叉主要依赖于 MutLγ 减数分裂重组中间解旋酶的组成部分 Mlh3，而在 处的 VDE 引发的交叉大多不依赖于 Mlh3。这些差异在缺乏染色体轴重塑酶 Pch2 的情况下消失，并且两个位置的交叉都部分依赖于 Mlh3。为了测试这些观察结果的普遍性，我们检查了在另外六个插入位点的情况，这些插入位点在 Hop1/Red1 富集、染色体大小以及与着丝粒和端粒的距离方面存在差异。所有六个位点的行为都与相似：绝大多数 VDE 引发的交叉都不依赖于 Mlh3。这表明，与之前的建议相反，减数分裂染色体轴蛋白的富集水平并不能单独决定哪种重组途径在 VDE 引发的减数分裂重组中产生交叉。在 突变体中，VDE 诱导的交叉中依赖于 Mlh3 的部分增加到以前在 Spo11 引发的交叉中观察到的水平，表明 Pch2 依赖性过程在控制 MutLγ 依赖性和 MutLγ 非依赖性交叉之间的平衡方面起着重要作用。
