Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Cell Rep. 2013 Sep 12;4(5):985-95. doi: 10.1016/j.celrep.2013.07.040. Epub 2013 Aug 30.
In Escherichia coli, bidirectional chromosomal replication is accompanied by the colocalization of sister replication forks. However, the biological significance of this mechanism and the key factors involved are still largely unknown. In this study, we found that a protein, termed CrfC, helps sustain the colocalization of nascent DNA regions of sister replisomes and promote chromosome equipartitioning. CrfC formed homomultimers that bound to multiple molecules of the clamp, a replisome subunit that encircles DNA, and colocalized with nascent DNA regions in a clamp-binding-dependent manner in living cells. CrfC is a dynamin homolog; however, it lacks the typical membrane-binding moiety and instead possesses a clamp-binding motif. Given that clamps remain bound to DNA after Okazaki fragment synthesis, we suggest that CrfC sustains the colocalization of sister replication forks in a unique manner by linking together the clamp-loaded nascent DNA strands, thereby laying the basis for subsequent chromosome equipartitioning.
在大肠杆菌中，双向染色体复制伴随着姐妹复制叉的共定位。然而，该机制的生物学意义和涉及的关键因素在很大程度上仍然未知。在这项研究中，我们发现一种称为 CrfC 的蛋白质有助于维持姐妹复制体的新生 DNA 区域的共定位，并促进染色体均等分配。CrfC 形成同源多聚体，与 DNA 环上的复制体亚基夹结合多个分子，并以依赖夹结合的方式与新生 DNA 区域在活细胞中共定位。CrfC 是一种动力蛋白同源物；然而，它缺乏典型的膜结合部分，而是具有夹结合基序。由于在冈崎片段合成后夹子仍与 DNA 结合，我们认为 CrfC 通过连接加载夹子的新生 DNA 链以独特的方式维持姐妹复制叉的共定位，从而为后续的染色体均等分配奠定了基础。
