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

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. [Display omitted] •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 In E. coli, bidirectional chromosomal replication is accompanied by the colocalization of sister replication forks. Katayama and colleagues now find that CrfC helps sustain sister fork colocalization and maintain chromosome equipartitioning. CrfC is a dynamin homolog lacking the membrane-binding moiety and possessing a replicase clamp-binding motif. Given that the clamp remains bound to the nascent DNA strands, we suggest that CrfC sustains the colocalization by linking the clamp-loaded DNA, thereby assisting in subsequent chromosome equipartitioning.