Chromosome Segregation Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
Bioinformatics and Biostatistics Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
Mol Cell. 2020 May 21;78(4):725-738.e4. doi: 10.1016/j.molcel.2020.03.017. Epub 2020 Apr 10.
Concomitant with DNA replication, the chromosomal cohesin complex establishes cohesion between newly replicated sister chromatids. Several replication-fork-associated "cohesion establishment factors," including the multifunctional Ctf18-RFC complex, aid this process in as yet unknown ways. Here, we show that Ctf18-RFC's role in sister chromatid cohesion correlates with PCNA loading but is separable from its role in the replication checkpoint. Ctf18-RFC loads PCNA with a slight preference for the leading strand, which is dispensable for DNA replication. Conversely, the canonical Rfc1-RFC complex preferentially loads PCNA onto the lagging strand, which is crucial for DNA replication but dispensable for sister chromatid cohesion. The downstream effector of Ctf18-RFC is cohesin acetylation, which we place toward a late step during replication maturation. Our results suggest that Ctf18-RFC enriches and balances PCNA levels at the replication fork, beyond the needs of DNA replication, to promote establishment of sister chromatid cohesion and possibly other post-replicative processes.
在 DNA 复制的同时，染色体黏合蛋白复合物在新复制的姐妹染色单体之间建立黏合。几种与复制叉相关的“黏合建立因子”，包括多功能 Ctf18-RFC 复合物，以未知的方式辅助这一过程。在这里，我们表明 Ctf18-RFC 在姐妹染色单体黏合中的作用与 PCNA 加载相关，但与复制检查点中的作用分离。Ctf18-RFC 以轻微偏好于前导链的方式加载 PCNA，这对于 DNA 复制不是必需的。相反，规范的 Rfc1-RFC 复合物优先将 PCNA 加载到滞后链上，这对于 DNA 复制至关重要，但对于姐妹染色单体黏合不是必需的。Ctf18-RFC 的下游效应物是黏合蛋白乙酰化，我们将其置于复制成熟的后期步骤中。我们的结果表明，Ctf18-RFC 在 DNA 复制之外，在复制叉处丰富和平衡 PCNA 水平，以促进姐妹染色单体黏合的建立，并可能促进其他复制后过程。
