A TetR-family transcriptional factor directly regulates the expression of a 3-methyladenine DNA glycosylase and physically interacts with the enzyme to stimulate its base excision activity in Mycobacterium bovis BCG [Microbiology]

February 7th, 2014 by Liu, L., Huang, C., He, Z.-G.

3 Methyladenine DNA glycosylase recognizes and excises a wide range of damaged bases and thus plays a critical role in base excision repair. However, knowledge on the regulation of DNA glycosylase in prokaryotes and eukaryotes is limited. In this study, we successfully characterized a TetR family transcriptional factor from Mycobacterium bovis bacillus Calmette Guerin (BCG), namely BCG0878c, which directly regulates the expression of 3-methyladenine DNA glycosylase (designated as MbAAG) and influences the base excision activity of this glycosylase at the post-translational level. Using electrophoretic mobility shift assay and DNase I footprinting experiments, we identified a conserved binding motif within the upstream region of MbAAG specifically recognized by BCG0878c. Significant downregulation of MbAAG was observed in BCG0878c overexpressed M. bovis BCG strains. By contrast, about 12 fold upregulation of MbAAG expression was found in BCG0878c-deleted mutant M. bovis BCG strains. β-galactosidase activity assays also confirmed these results. Thus, BCG0878c can function as a negative regulator of MbAAG expression. In addition, the regulator was shown to physically interact with MbAAG to enhance the ability of the glycosylase to bind damaged DNA. Interaction between the two proteins was further found to facilitate AAG catalyzed removal of hypoxanthine from DNA. These results indicate that a TetR family protein can dually regulate the function of 3-methyladenine DNA glycosylase in M. bovis BCG both at the transcriptional and posttranslational levels. These findings enhance our understanding of the expression and regulation of AAG in mycobacteria.
  • Posted in Journal of Biological Chemistry, Publications
  • Comments Off on A TetR-family transcriptional factor directly regulates the expression of a 3-methyladenine DNA glycosylase and physically interacts with the enzyme to stimulate its base excision activity in Mycobacterium bovis BCG [Microbiology]