1887

Abstract

The incorporation of dUMP during replication or the deamination of cytosine in DNA results in the occurrence of uracils in genomes. To maintain genomic integrity, uracil DNA glycosylases (UDGs) excise uracil from DNA and initiate the base-excision repair pathway. Here, we cloned, purified and biochemically characterized a family 5 UDG, UdgB, from to allow us to use it as a model organism to investigate the physiological significance of the novel enzyme. Studies with knockout strains showed that compared with the wild-type parent, the mutation rate of the strain was approximately twofold higher, whereas the mutation rate of a strain deficient in the family 1 UDG ( ) was found to be ∼8.4-fold higher. Interestingly, the mutation rate of the double-knockout ( / ) strain was remarkably high, at ∼19.6-fold. While CG to TA mutations predominated in the and / strains, AT to GC mutations were enhanced in the strain. The / strain was notably more sensitive to acidified nitrite and hydrogen peroxide stresses compared with the single knockouts ( or ). These observations reveal a synergistic effect of UdgB and Ung in DNA repair, and could have implications for the generation of attenuated strains of .

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2010-03-01
2020-02-28
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