Escherichia coli DNA repair genes radA and sms are the same gene

Abstract

Escherichia coli strains carrying radA100 or sms mutations were identical in their sensitivities to either methyl methanesulfonate or UV radiation treatment and in their plasmid complementation patterns for UV radiation survival. DNA sequencing analysis of the radA mutant and radA ؉ strains and comparison of their sequences with the published sms gene sequence showed the radA mutant to differ only by a G-to-A transition mutation, which is predicted to change a cysteine in a zinc-finger motif to tyrosine. The sms gene is concluded to be identical to the previously described radA gene.The radA100 mutation (named for its role in radiation resistance) was isolated because it made Escherichia coli cells sensitive to gamma radiation (3). This mutation maps close to the serB locus (3) and has been placed at 99.5 min on the E. coli K-12 linkage map (1). Log-phase radA mutant cells show increased sensitivity to X rays, methyl methanesulfonate (MMS), and UV radiation when grown in rich medium but not when grown in minimal medium (3). Rich medium-grown radA100 cells are also 30% deficient in their ability to repair X-rayinduced DNA double-strand breaks compared with radA ϩ cells (15).Ten years after the description of the radA gene, Neuwald et al. (11) described the sms gene (named for sensitivity to MMS), which is cotranscribed with the serB gene but is not required for serine biosynthesis. The sms gene is 1,380 bp long, and sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis shows a 55-kDa product (11). It is of general interest that certain Sms protein domains show substantial similarity to different motifs of Lon protease and RecA protein (8, 11), two proteins that have long been known for their roles in gene regulation and DNA repair (e.g., reference 6). The purpose of this work was to test the hypothesis that the radA and sms genes are identical.(This paper represents partial fulfillment by Y. Song of the requirements for a Master's thesis from Truman State University, Kirksville, Mo., 1996.) Effects of radA100 and sms mutations on survival. Earlier studies of the radA and sms mutations involved distantly related E. coli strains. In this study, undesired strain differences were minimized by transducing both the radA and sms mutations into the same parental uvr ϩ and uvrA6 strains for phenotype comparison studies (all strains and plasmids used in this study are listed in Table 1). Although the original sms-1 gene disruption mutant (AN1) has apparently been lost, George V. Stauffer kindly provided a similarly constructed mutant whose sms mutation was used in our studies. The uvrA radA and uvrA sms strains showed essentially identical sensitivities to MMS, and they required only 66 and 56% as much MMS treatment, respectively, as the uvrA control strain to yield a surviving fraction of 10%; i.e., their respective D 10 ratios were 0.66 and 0.56 (Fig. 1a).The radA mutation has been reported to sensitize a wildtype (uvrA ϩ ) strain to UV radiation (3), while the sms mutation reportedly has no effect (11). W...

Role for radA/sms in Recombination Intermediate Processing in Escherichia coli

“…The function of RadA's putative Zn finger is important in repair, since the original radA100 mutation results in a cysteine-to-tyrosine change at one of the invariant residues (46). In our DNA damage survival assays, the radA100 mutant was as sensitive as two null mutants in radA to the alkylating agent MMS.…”

“…The original allele of radA is radA100, which encodes a mutation in one of the conserved cysteine residues in the putative zinc finger of the RadA protein (46). We generated two additional mutant alleles: radA1::kan, a simple insertion, and rad3⌬::FRT, a complete and precise deletion of the entire open reading frame.…”

“…The sms gene was defined as an open reading frame downstream of, and coregulated with, serB, whose inactivation caused slight sensitivity to methyl methanesulfonate (MMS) (39). Later, sms and radA were identified as the same gene (46).…”

AnkB, a Periplasmic Ankyrin-Like Protein in Pseudomonas aeruginosa , Is Required for Optimal Catalase B (KatB) Activity and Resistance to Hydrogen Peroxide

“…1). We then identified a gene downstream of the inverted repeat that was 70% identical to the radA gene of E. coli (49). The radA gene in E. coli encodes a protein that repairs DNA damaged (alkylated) by gamma irradiation.…”

Radiation-sensitive Gene A (RadA) Targets DisA, DNA Integrity Scanning Protein A, to Negatively Affect Cyclic Di-AMP Synthesis Activity in Mycobacterium smegmatis

“…An important aspect of the current study is the discovery of a link between RadA and control of c-di-AMP synthesis. The radA/sms gene was initially identified as a radiation-sensitive gene in E. coli and its main function was considered to be to play a synergistic role in DNA damage repair and recombination (29,30). Mutation of radA has been reported to confer profound sensitivity to various DNA-damaging agents in E. coli (30).…”