PriA-directed assembly of a primosome on D loop DNA

Escherichia coli strains carrying null mutations in priA are chronically in duced for the SOS response and are defective in homologous recombination, r epair of UV damaged DNA, double-strand break repair, and both induced and c onstitutive stable DNA replication. This led to the proposal that PriA dire cted replication fork assembly at D loops formed by the homologous recombin ation machinery. The demonstration that PriA specifically recognized and bo und D loop DNA supported this hypothesis. Using DNA footprinting as an assa y, we show here that PriA also directs the assembly of a phi X174-type prim osome on D loop DNA. The ability to load a complete primosome on D loop DNA is a step necessary for replication fork assembly.