Misrepair of overlapping daughter strand gaps as a possible mechanism for UV induced mutagenesis in UVR strains of Escherichia coli: a general model for induced mutagenesis by misrepair (SOS repair) of closely spaced DNA lesions.

It has been previously reported that an inducible form of post-replication repair appeared to be required for UV induced mutagenesis in a uvrA strain of Escherichia coli. It is shown here that the numbers of daughter strand gaps requiring inducible repair were similar to the numbers calculated to be overlapping one another in opposite daughter chromosomes. An estimation of survival with no repair of these gaps resembled the survival predicted with no mutagenesis. It is the thus proposed that inducible post-replication repair causes mutagenesis by the repair of overlapping daughter strand gaps. A general model for induced mutagenesis is presented. It is proposed that (a) some DNA lesions introduced by any DNA damaging agent may be close enough to interfere with constitutive repair replication of each other, (b) these lesions induce a repair system (SOS repair) which involves the recA+ lexA+ and polC+ genes (c) repair and concomitant mutagenesis occurs during repair replication by the insertion of mismatched bases opposite the noncoding DNA lesions.