酵母减数分裂中 HO 核酸内切酶引发的重组无法促进同源着丝粒配对，且不受 Dmc1 重组酶的限制,G3: Genes, Genomes, Genetics

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酵母减数分裂中 HO 核酸内切酶引发的重组无法促进同源着丝粒配对，且不受 Dmc1 重组酶的限制
G3: Genes, Genomes, Genetics ( IF 2.1 ) Pub Date : 2019-01-16 , DOI: 10.1534/g3.118.200641
Lina Yisehak ₁ , Amy J MacQueen ₂

Affiliation

摘要减数分裂期间的交叉重组伴随着显着的染色体重组。在酿酒酵母中，Spo11 酯交换酶引发的减数分裂重组导致先前未关联的同源着丝粒之间稳定的成对关联，随后通过联会复合体 (SC) 组装实现同源轴的紧密排列。然而，重组和整体减数分裂染色体重组之间的分子关系仍然知之甚少。在芽殖酵母中，一个问题是为什么 SC 组装最早在着丝粒区域启动，而启动重组的 DNA 双链断裂 (DSB) 发生在整个基因组范围内。我们将位点特异性 HO 核酸内切酶靶向酿酒酵母最长染色体上的不同位置，以探究减数分裂 DSB 与着丝粒的接近程度是否会影响其促进同源着丝粒配对和 SC 组装的能力。我们发现，HO 介导的 DSB 修复不会促进同源着丝粒配对，也不会促进 spo11 减数分裂核中 SC 组装的任何程度，无论其与着丝粒的距离如何。通过腐草霉素暴露而集体诱导的 DSB 同样不会促进同源着丝粒配对，也不会促进稳健的 SC 组装。有趣的是，与 Spo11 相比，HO 启动的同源间重组不受减数分裂激酶 Mek1 丢失的影响，并且不限于使用减数分裂特异性 Dmc1 重组酶。这些结果强化了之前提出的观点，即（至少某些）Spo11 DSB 可能专门用于激活以下机制：1）通过同源着丝粒配对和 SC 组装增强同源染色体排列，2）将 Dmc1 确立为主要链交换酶。

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HO Endonuclease-Initiated Recombination in Yeast Meiosis Fails To Promote Homologous Centromere Pairing and Is Not Constrained To Utilize the Dmc1 Recombinase

AbstractCrossover recombination during meiosis is accompanied by a dramatic chromosome reorganization. In Saccharomyces cerevisiae, the onset of meiotic recombination by the Spo11 transesterase leads to stable pairwise associations between previously unassociated homologous centromeres followed by the intimate alignment of homologous axes via synaptonemal complex (SC) assembly. However, the molecular relationship between recombination and global meiotic chromosome reorganization remains poorly understood. In budding yeast, one question is why SC assembly initiates earliest at centromere regions while the DNA double strand breaks (DSBs) that initiate recombination occur genome-wide. We targeted the site-specific HO endonuclease to various positions on S. cerevisiae’s longest chromosome in order to ask whether a meiotic DSB’s proximity to the centromere influences its capacity to promote homologous centromere pairing and SC assembly. We show that repair of an HO-mediated DSB does not promote homologous centromere pairing nor any extent of SC assembly in spo11 meiotic nuclei, regardless of its proximity to the centromere. DSBs induced en masse by phleomycin exposure likewise do not promote homologous centromere pairing nor robust SC assembly. Interestingly, in contrast to Spo11, HO-initiated interhomolog recombination is not affected by loss of the meiotic kinase, Mek1, and is not constrained to use the meiosis-specific Dmc1 recombinase. These results strengthen the previously proposed idea that (at least some) Spo11 DSBs may be specialized in activating mechanisms that both 1) reinforce homologous chromosome alignment via homologous centromere pairing and SC assembly, and 2) establish Dmc1 as the primary strand exchange enzyme.

更新日期：2019-01-16

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