Non-mutability by ultraviolet light in uvrD recB derivatives of Escherichia coli WP2 uvrA is due to inhibition of RecA protein activation

Abstract

The deficiency in UV mutagenesis in uvrD3 recB21 strains of E. coli is almost completely overcome by constitutive activation of RecA protein and expression of the SOS system (by recA730 or 43°C treated recA441 lexA71). When SOS was expressed but RecA protein not self-activated ( recA441 lexA71 at 30°C), uvrD3 recB21 still reduced UV mutagenesis at low doses. The uvrD3 recB21) combination is therefore inhibiting activation of RecA protein. It is suggested that the DNA unwinding activity of the products of the uvrD and recB genes may be involved in generating single-stranded DNA needed to activate RecA protein both for the cleavage of LexA repressor and for a futher role in UV mutagenesis.