Meiosis-specific Rec114−Mei4 and Mer2 complexes are thought to enable Spo11-mediated DNA double-strand break (DSB) formation through a mechanism that involves DNA-dependent condensation. However, the structure, molecular properties, and evolutionary conservation of Rec114−Mei4 and Mer2 are unclear. Here, we present AlphaFold models of Rec114−Mei4 and Mer2 complexes supported by nuclear magnetic resonance (NMR) spectroscopy, small-angle X-ray scattering (SAXS), and mutagenesis. We show that dimers composed of the Rec114 C terminus form α-helical chains that cup an N-terminal Mei4 α helix, and that Mer2 forms a parallel homotetrameric coiled coil. Both Rec114−Mei4 and Mer2 bind preferentially to branched DNA substrates, indicative of multivalent protein–DNA interactions. Indeed, the Rec114−Mei4 interaction domain contains two DNA-binding sites that point in opposite directions and drive condensation. The Mer2 coiled-coil domain bridges coaligned DNA duplexes, likely through extensive electrostatic interactions along the length of the coiled coil. Finally, we show that the structures of Rec114−Mei4 and Mer2 are conserved across eukaryotes, while DNA-binding properties vary significantly. This work provides insights into the mechanism whereby Rec114−Mei4 and Mer2 complexes promote the assembly of the meiotic DSB machinery and suggests a model in which Mer2 condensation is the essential driver of assembly, with the DNA-binding activity of Rec114−Mei4 playing a supportive role.

中文翻译：

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减数分裂 Rec114−Mei4 和 Mer2 复合物结构和功能的进化保守性

减数分裂特异性 Rec114−Mei4 和 Mer2 复合物被认为能够通过涉及 DNA 依赖性缩合的机制实现 Spo11 介导的 DNA 双链断裂 (DSB) 形成。然而，Rec114−Mei4 和 Mer2 的结构、分子特性和进化保守性尚不清楚。在这里，我们提出了由核磁共振 (NMR) 光谱、小角 X 射线散射 (SAXS) 和诱变支持的 Rec114−Mei4 和 Mer2 复合物的 AlphaFold 模型。我们发现，由 Rec114 C 末端组成的二聚体形成 α 螺旋链，该螺旋链包围 N 末端 Mei4​​ α 螺旋，而 Mer2 形成平行的同源四聚体卷曲线圈。Rec114−Mei4 和 Mer2 均优先结合分支 DNA 底物，表明多价蛋白质-DNA 相互作用。事实上，Rec114−Mei4 相互作用结构域包含两个指向相反方向并驱动缩合的 DNA 结合位点。Mer2 卷曲螺旋结构域可能通过沿着卷曲线圈长度的广泛静电相互作用来桥接对齐的 DNA 双链体。最后，我们证明 Rec114−Mei4 和 Mer2 的结构在真核生物中是保守的，而 DNA 结合特性却存在显着差异。这项工作提供了对 Rec114−Mei4 和 Mer2 复合物促进减数分裂 DSB 机器组装的机制的见解，并提出了一个模型，其中 Mer2 缩合是组装的基本驱动力，Rec114−Mei4 的 DNA 结合活性起到支持作用。角色。