Hop2-Mnd1 condenses DNA to stimulate the synapsis phase of DNA strand exchange.
Hop2-Mnd1 condenses DNA to stimulate the synapsis phase of DNA strand exchange.
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DOI：
10.1016/j.bpj.2010.10.028
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发表时间：
2010-12
影响因子：
3.4
通讯作者：
R. Pezza;R. Camerini‐Otero;P. Bianco
中科院分区：
文献类型：
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作者：
R. Pezza;R. Camerini‐Otero;P. Bianco
Hop2-Mnd1 是一种减数分裂重组介质，可刺激 Dmc1 和 Rad51 的 DNA 链入侵。为了了解这种刺激的生化机制，我们使用光镊和视频荧光显微镜直接观察了作用于双链 DNA 单分子的异二聚体。结果表明，Hop2-Mnd1异二聚体通过形成亮点或DNA凝聚物有效地凝聚双链DNA。 DNA 的缩合是 Hop2-Mnd1 浓度依赖性的、可逆的，并且对异二聚体具有特异性，因为单独作用的 Hop2 和 Mnd1 都不能促进该反应。结果还表明，在二价金属离子存在下，DNA缩合的限速成核步骤被克服，优先顺序如下：Mn2+>Mg2+>Ca2+。 Hop2-Mnd1/Dmc1/单链DNA核蛋白丝也以异二聚体浓度依赖性方式浓缩双链DNA。重要的是，浓度依赖性与 DNA 链交换中的浓度依赖性相似。我们认为快速 DNA 浓缩是刺激突触的关键因素，而解浓缩可能促进入侵步骤和/或随后的分支迁移过程。
Hop2-Mnd1 is a meiotic recombination mediator that stimulates DNA strand invasion by both Dmc1 and Rad51. To understand the biochemical mechanism of this stimulation, we directly visualized the heterodimer acting on single molecules of duplex DNA using optical tweezers and video fluorescence microscopy. The results show that the Hop2-Mnd1 heterodimer efficiently condenses double-stranded DNA via formation of a bright spot or DNA condensate. The condensation of DNA is Hop2-Mnd1 concentration-dependent, reversible, and specific to the heterodimer, as neither Hop2 nor Mnd1 acting alone can facilitate this reaction. The results also show that the rate-limiting nucleation step of DNA condensation is overcome in the presence of divalent metal ions, with the following order of preference: Mn2+>Mg2+>Ca2+. Hop2-Mnd1/Dmc1/single-stranded DNA nucleoprotein filaments also condense double-stranded DNA in a heterodimer concentration-dependent manner. Of importance, the concentration dependence parallels that seen in DNA strand exchange. We propose that rapid DNA condensation is a key factor in stimulating synapsis, whereas decondensation may facilitate the invasion step and/or the ensuing branch migration process.