UvrA and UvrB enhance mutations induced by oxidized deoxyribonucleotides

Abstract

Oxidatively damaged DNA precursors (deoxyribonucleotides) are formed by reactive oxygen species. After the damaged DNA precursors are incorporated into DNA, they might be removed by DNA repair enzymes. In this study, to examine whether a nucleotide excision repair enzyme, Escherichia coli UvrABC, could suppress the mutations induced by oxidized deoxyribonucleotides in vivo, oxidized DNA precursors, 8-hydroxy-2´-deoxyguanosine 5´-triphosphate and 2-hydroxy-2´-deoxyadenosine 5´-triphosphate, were introduced into uvrA, uvrB, and uvrC E. coli strains, and mutations in the chromosomal rpoB gene were analyzed. Unexpectedly, these oxidized DNA precursors induced mutations only slightly in the uvrA and uvrB strains. In contrast, effect of the uvrC-deficiency was not observed. Next, mutT, mutT/uvrA, and mutT/uvrB E. coli strains were treated with H 2 O 2 , and the rpoB mutant frequencies were calculated. The frequency of the H 2 O 2 -induced mutations was increased in all of the strains tested; however, the increase was threeto four-fold lower in the mutT/uvrA and mutT/uvrB strains than in the mutT strain. Thus, UvrA and UvrB are involved in the enhancement, but not in the suppression, of the mutations induced by these oxidized deoxyribonucleotides. These results suggest a novel role for UvrA and UvrB in the processing of oxidative damage.

The nucleotide excision repair (NER) system of Helicobacter pylori: Role in mutation prevention and chromosomal import patterns after natural transformation

“…These results seem surprising, considering that one key function of the NER system is to limit mutations by repairing DNA lesions. Our results are, however, consistent with previous findings in E. coli , where decreased mutation frequencies were reported in uvrA and uvrB mutants after treatment with oxidized deoxyribonucleotides, while mutation rates were unaffected in a uvrC mutant [31]. Under non-damage-inducing conditions, E. coli mutants in uvrA uvrB and uvrC exhibited a lower mutation rate [24].…”

Molecular Mechanisms of the Whole DNA Repair System: A Comparison of Bacterial and Eukaryotic Systems

“…Despite the lack of sequence homology, the endonuclease domain has an RNase H-like fold. We established the methods of purification of UvrC from T. thermophilus (ttUvrC; TTHA1568), and Hori et al developed an in vitro reconstitution system of NER using purified ttUvrA, ttUvrB, and ttUvrC [131]. The ttUvrABC system can recognize a (6-4) thymine dimer and excise the affected strand; however, it does not excise a strand containing 8-hydroxy-2′-deoxyguanine or 2-hydroxy-2′-deoxyadenine [131].…”

“…UvrA contains three zinc ions. It has been reported that ttUvrA and ttUvrB can recognize bulky adducts, such as tetramethylrhodamine and tetramethylrhodamine ethyl ester, and (6-4) pyrimidine dimer [113, 131]. Furthermore, it has been shown that ttUvrA can interact with the ATL protein, but the physiological significance of this interaction remains unclear [37].…”

Mutagenicity of oxidized DNA precursors in living cells: Roles of nucleotide pool sanitization and DNA repair enzymes, and translesion synthesis DNA polymerases

“…The E. coli UvrA and UvrB proteins, which are involved in nucleotide excision repair, enhanced the mutations induced by 8-OH-dGTP and 2-OH-dATP by an unknown mechanism(s) [48].…”