A combinatorial role for MutY and Fpg DNA glycosylases in mutation avoidance in Mycobacterium smegmatis

作者：Hassim Farzanah; Papadopoulos Andrea O; Kana Bavesh D; Gordhan Bhavna G^*

来源：Mutation Research-Fundamental and Molecular Mechanisms of Mutagenesis, 2015, 779: 24-32.

DOI：10.1016/j.mrfmmm.2015.06.002

• Mycobacterium tuberculosis
• 8-OxoGua
• Formamidopyrimidine N-DNA glycosylase
• Muty
• Mutagenesis
• DNA repair

Hydroxyl radical ((OH)-O-center dot) among reactive oxygen species cause damage to nucleobases with thymine being the most susceptible, whilst in contrast, the singlet oxygen (O-1(2)) targets only guanine bases. The high GC content of mycobacterial genomes predisposes these organisms to oxidative damage of guanine. The exposure of cellular DNA to (OH)-O-center dot and one-electron oxidants results in the formation of two main degradation products, the pro-mutagenic 8-oxo-7,8-dihydroguanine (8-oxoGua) and the cytotoxic 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua). These lesions are repaired through the base excision repair (BER) pathway and we previously, demonstrated a combinatorial role for the mycobacterial Endonuclease III (Nth) and the Nei family of DNA glycosylases in mutagenesis. In addition, the formamidopyrimidine (Fpg/MutM) and MutY DNA glycosylases have also been implicated in mutation avoidance and BER in mycobacteria. In this study, we further investigate the combined role of MutY and the Fpg/Nei DNA glycosylases in Mycobacterium smegmatis and demonstrate that deletion of mutY resulted in enhanced sensitivity to oxidative stress, an effect which was not exacerbated in Delta fpg1 Delta fpg2 or Delta nei1 Delta nei2 double mutant backgrounds. However, combinatorial loss of the mutY, fpg1 and fpg2 genes resulted in a significant increase in mutation rates suggesting interplay between these enzymes. Consistent with this, there was a significant increase in C -> A mutations with a corresponding change in cell morphology of rifampicin resistant mutants in the Delta fpg1 Delta fpg2 Delta mutY deletion mutant. In contrast, deletion of mutY together with the nei homologues did not result in any growth/survival defects or changes in mutation rates. Taken together these data indicate that the rnycobacterial mutY, in combination with the Fpg DNA N-glycosylases, plays an important role in controlling mutagenesis under oxidative stress.

• 出版日期2015-9