Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
Mol Cell. 2019 May 16;74(4):664-673.e5. doi: 10.1016/j.molcel.2019.02.027. Epub 2019 Mar 25.
Cohesin is a conserved, ring-shaped protein complex that topologically embraces DNA. Its central role in genome organization includes functions in sister chromatid cohesion, DNA repair, and transcriptional regulation. Cohesin loading onto chromosomes requires the Scc2-Scc4 cohesin loader, whose presence on chromatin in budding yeast depends on the RSC chromatin remodeling complex. Here we reveal a dual role of RSC in cohesin loading. RSC acts as a chromatin receptor that recruits Scc2-Scc4 by a direct protein interaction independent of chromatin remodeling. In addition, chromatin remodeling is required to generate a nucleosome-free region that is the substrate for cohesin loading. An engineered cohesin loading module can be created by fusing the Scc2 C terminus to RSC or to other chromatin remodelers, but not to unrelated DNA binding proteins. These observations demonstrate the importance of nucleosome-free DNA for cohesin loading and provide insight into how cohesin accesses DNA during its varied chromosomal activities.
黏合蛋白是一种保守的、环形的蛋白质复合物，能够对 DNA 进行拓扑包裹。其在基因组组织中的核心作用包括姐妹染色单体黏合、DNA 修复和转录调控。黏合蛋白在染色体上的加载需要 Scc2-Scc4 黏合蛋白加载器，而在芽殖酵母中，染色质上 Scc2-Scc4 黏合蛋白加载器的存在依赖于 RSC 染色质重塑复合物。在这里，我们揭示了 RSC 在黏合蛋白加载中的双重作用。RSC 作为一种染色质受体，通过独立于染色质重塑的直接蛋白质相互作用来招募 Scc2-Scc4。此外，染色质重塑对于生成黏合蛋白加载的底物无核小体区域是必需的。通过将 Scc2 C 末端融合到 RSC 或其他染色质重塑因子上，但不能融合到不相关的 DNA 结合蛋白上，可以构建一个工程化的黏合蛋白加载模块。这些观察结果表明了无核小体 DNA 对黏合蛋白加载的重要性，并深入了解了黏合蛋白在其各种染色体活动中如何访问 DNA。
