Mutagenic DNA repair in enterobacteria

Abstract

Sixteen species of enterobacteria have been screened for mutagenic DNA repair activity. In Escherichia coli, mutagenic DNA repair is encoded by the umuDC operon. Synthesis of UmuD and UmuC proteins is induced as part of the SOS response to DNA damage, and after induction, the UmuD protein undergoes an autocatalytic cleavage to produce the carboxy-terminal UmuD' fragment needed for induced mutagenesis. The presence of a similar system in other species was examined by using a combined approach of inducible-mutagenesis assays, cross-reactivity to E. coli UmuD and UmuD' antibodies to test for induction and cleavage of UmuD-like proteins, and hybridization with E. coli and Salmonella typhimurium umu DNA probes to map umu-like genes. The results indicate a more widespread distribution of mutagenic DNA repair in other species than was previously thought. They also show that umu loci can be more complex in other species than in E. coli. Differences in UV-induced mutability of more than 200-fold were seen between different species of enteric bacteria and even between multiple natural isolates of E. coli, and yet some of the species which display a poorly mutable phenotype still have umu-like genes and proteins.

Genetic responses of the thermophilic archaeon Sulfolobus acidocaldarius to short-wavelength UV light

“…D. radiodurans, for example, has very effective repair of UV lesions but lacks an error-prone form of repair and is not mutated by even lethal doses of UV (23). Indeed, even the phylogenetically close relatives within the enteric bacteria differ by factors of up to 200 in their ability to be mutated by UV (29). E. coli, used here as a control strain, is the most UV-mutable species of this group (29), yet its error-prone repair makes little contribution in wild-type cells to the overall survival of UV radiation (32,34).…”

The genetic requirements for UmuDC-mediated cold sensitivity are distinct from those for SOS mutagenesis

“…On the basis of the lack of an obvious evolutionary selection for proteins that promote mutagenesis and the fact that there are several bacterial species that contain umuDC homologs but are not mutable by UV (41), it has been previously suggested VOL. 178, 1996 UmuDC-MEDIATED COLD SENSITIVITY 4409…”

A rapid method for cloning mutagenic DNA repair genes: isolation of umu-complementing genes from multidrug resistance plasmids R391, R446b, and R471a

“…These mutagenesis proteins are induced as part of the cellular SOS response to DNA damage. Over the past few years, molecular and genetic studies have revealed umu-like genes and proteins in a number of bacterial strains (27,45). Interestingly, these mutagenic DNA repair genes appear to reside in two locations: either chromosomally, such as the umuDC genes from Eschenichia coli and Salmonella typhimurium (20,37,49,53), or on certain naturally occurring plasmids, such as the mucAB, impCAB, and samAB operons (23,30,37).…”