Synergistic effects of UdgB and Ung in mutation prevention and protection against commonly encountered DNA damaging agents in Mycobacterium smegmatis

Malshetty, Vidyasagar S and Jain, Ruchi and Srinath, Thiruneelakantan and Kurthkoti, Krishna and Varshney, Umesh (2010) Synergistic effects of UdgB and Ung in mutation prevention and protection against commonly encountered DNA damaging agents in Mycobacterium smegmatis. In: Microbiology, 156 (Part 3). pp. 940-949.

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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 Mycobacterium smegmatis 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 udgB(-) strain was approximately twofold higher, whereas the mutation rate of a strain deficient in the family 1 UDG (ung(-)) was found to be similar to 8.4-fold higher. Interestingly, the mutation rate of the double-knockout (ung(-)ludgB(-)) strain was remarkably high, at similar to 19.6-fold. While CG to TA mutations predominated in the ung(-) and ung(-)/udgb(-) strains, AT to GC mutations were enhanced in the udgB(-) strain. The ung(-)/udgB(-) strain was notably more sensitive to acidified nitrite and hydrogen peroxide stresses compared with the single knockouts (ung(-) or udgB(-)). These observations reveal a synergistic effect of UdgB and Ung in DNA repair, and could have implications for the generation of attenuated strains of Mycobacterium tuberculosis.

Item Type:	Journal Article
Publication:	Microbiology
Publisher:	Society for General Microbiology
Additional Information:	Copyright of this article belongs to Society for General Microbiology.
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited:	09 Jun 2010 07:09
Last Modified:	19 Sep 2010 05:59
URI:	http://eprints.iisc.ac.in/id/eprint/27118

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