ALTERED SOS INDUCTION ASSOCIATED WITH MUTATIONS IN RECF, RECO AND RECR

The SOS system of Escherichia coli aids survival following damage to D NA by promoting DNA repair while cell division is delayed. Induction o f the SOS response is dependent on RecA and also on the product of rec F. We show that normal induction also requires the products of recO an d recR. SOS induction was monitored using a sfiA-lacZ fusion strain. I nduction was delayed to a similar degree by mutation in recF, recO or recR. A similar effect was observed following overexpression of RecR f rom a recombinant recR(+) plasmid. We show that the overexpression of RecR also reduces the UV resistance of a recBC sbcBC strain and of a s fiA strain, but not of a rec(+) sfiA(+) strain. The implications of th ese data for the kinetics of DNA repair are discussed.