Molecular Interactions in PriC‐mediated DNA Replication Restart

Abstract

DNA replication restart is an essential process in bacteria that reloads DNA replication complexes (replisomes) that have ejected prematurely from replication forks due to encounters with impassable DNA damage or protein complexes. In E. coli and related bacterial species, the “replication restart proteins” (PriA, PriB, PriC, DnaT, and Rep) catalyze this activity. The 20‐kDa PriC protein is unique among these proteins in that it can mediate in vitro replisome reloading in the absence of other replication restart proteins. Precisely how PriC recognizes abandoned DNA replication fork structures and directs replisome reloading is currently unknown. We have found that the single‐strand DNA‐binding protein (SSB) forms a direct complex with PriC that we hypothesize is important for directing PriC reloading activities to abandoned DNA replication forks. PriC variants that fail that to bind SSB (but that retain DNA binding) were identified to test this hypothesis. Consistent with an essential role for the PriC/SSB interaction, these variants cannot catalyze the first step of replication restart (loading the DnaB helicase onto an SSB‐bound synthetic replication fork) in vitro. On‐going experiments aim to determine the solution structure of PriC and to assess the importance of complex formation with SSB in PriC‐mediated DNA replication restart in vivo. Research supported by GM068061 and T32‐GM07215.