A Replicase Clamp-Binding Dynamin-like Protein Promotes Colocalization of Nascent DNA Strands and Equipartitioning of Chromosomes in E. coli

• An E. coli dynamin homolog (CrfC) is required for chromosomal positioning
• CrfC binds multiple molecules of the clamp, a DNA-binding replisome subunit
• CrfC colocalizes with nascent DNA after the passage of sister replication forks
• CrfC sustains the colocalization of the nascent DNA in a clamp-dependent manner

SummaryIn 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.

Graphical AbstractFigure optionsDownload as PowerPoint slide