title: PriA helicase and SSB interact physically and functionally.
abstract: PriA helicase is the major DNA replication restart initiator in Escherichia coli and acts to reload the replicative helicase DnaB back onto the chromosome at repaired replication forks and D-loops formed by recombination. We have discovered that PriA-catalysed unwinding of branched DNA substrates is stimulated specifically by contact with the single-strand DNA binding protein of E.coli, SSB. This stimulation requires binding of SSB to the initial DNA substrate and is effected via a physical interaction between PriA and the C-terminus of SSB. Stimulation of PriA by the SSB C-terminus may act to ensure that efficient PriA-catalysed reloading of DnaB occurs only onto the lagging strand template of repaired forks and D-loops. Correlation between the DNA repair and recombination defects of strains harbouring an SSB C-terminal mutation with inhibition of this SSB-PriA interaction in vitro suggests that SSB plays a critical role in facilitating PriA-directed replication restart. Taken together with previous data, these findings indicate that protein-protein interactions involving SSB may coordinate replication fork reloading from start to finish.
authors.affiliation: School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Cadman
authors.forename: Peter
authors.initials: P
authors.lastname: McGlynn
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D053488:DnaB Helicases; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C476430:SSB protein, E coli; D004247:DNA; D000251:Adenosine Triphosphatases; C506730:dnaB protein, E coli; C506743:priA protein, E coli; D004265:DNA Helicases; D053488:DnaB Helicases