The synaptonemal complex (SC) keeps homologous chromosomes in close alignment during meiotic recombination. A hallmark of the SC is the presence of its constituent protein SYCP3 on the chromosome axis. During SC assembly, SYCP3 is deposited on both axes of the homologue pair, forming axial elements that fuse into the lateral element (LE) in the tripartite structure of the mature SC. We have used cryo-electron tomography and atomic force microscopy to study the mechanism of assembly and DNA binding of the SYCP3 fibre. We find that the three-dimensional architecture of the fibre is built on a highly irregular arrangement of SYCP3 molecules displaying very limited local geometry. Interaction between SYCP3 molecules is driven by the intrinsically disordered tails of the protein, with no contact between the helical cores, resulting in a flexible fibre assembly. We demonstrate that the SYCP3 fibre can engage in extensive interactions with DNA, indicative of an efficient mechanism for incorporation of DNA within the fibre. Our findings suggest that SYCP3 deposition on the chromosome axis might take place by polymerization into a fibre that is fastened to the chromosome surface via DNA binding.

中文翻译：

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SYCP3 纤维的分子结构及其与 DNA 的相互作用。

联会复合体 (SC) 在减数分裂重组期间使同源染色体保持紧密排列。SC 的一个标志是其组成蛋白 SYCP3 在染色体轴上的存在。在 SC 组装过程中，SYCP3 沉积在同系物对的两个轴上，形成轴向元件，融合到成熟 SC 三方结构中的横向元件 (LE)。我们使用低温电子断层扫描和原子力显微镜来研究 SYCP3 纤维的组装和 DNA 结合机制。我们发现纤维的三维结构建立在高度不规则排列的 SYCP3 分子之上，显示出非常有限的局部几何形状。SYCP3 分子之间的相互作用是由蛋白质本质上无序的尾部驱动的，螺旋核心之间没有接触，从而形成柔性纤维组件。我们证明 SYCP3 纤维可以与 DNA 进行广泛的相互作用，表明在纤维中掺入 DNA 的有效机制。我们的研究结果表明，SYCP3 在染色体轴上的沉积可能是通过聚合成纤维而发生的，该纤维通过 DNA 结合固定在染色体表面。