RRM
2010 Rustbelt RNA Meeting
RRM
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Poster abstracts
Abstract:
Studies of the yeast tRNA methyltransferase Trm4p revealed the partial reversibility of RNA m5C methyltransferases that function with a dual-cysteine mechanism. Trm4p forms covalent complexes with methylated tRNA in the presence of S-adenosylhomocysteine and complex formation increases as the pH becomes more acidic. We anticipate that YebU (RsmF), a bacterial m5C methyltransferase is also partially reversible. YebU modifies cytosine 1407 in 16S rRNA, but only in the context of an intact 30S subunit. A YebU-30S complex would preclude association of the 30S and 50S ribosomal subunits, resulting in blocked translation. Although this pH based translational inhibition is theoretical, it could be significant in strongly acidic environments, thereby influencing acid survival of YebU expressing bacteria like E. coli and Salmonella.
Here we provide evidence that YebU has a role in acid survival. The growth of E. coli strain CP79ÄyebU was compared to the growth of the parental CP79 strain in buffered rich media at various pH values. Multiple experiments revealed a substantial growth difference between the mutant and wild type strains at pH values just above the acid limit for growth. The difference was observed when either stationary or log phase cells were shifted to low pH, but the effects were stronger and longer lasting with log phase cells. Plating experiments with log phase cells demonstrated only 5% survival of the CP79ÄyebU cells after 24 hours at pH 4.6. Growth studies with the YebU mutant from the Keio knockout collection showed similar growth deficiencies relative to the corresponding parental strain, therefore the results obtained are not specific to the CP79 strain. The results have encouraged us to seek biochemical evidence for translational regulation by YebU and to further pursue the general concept that RNA m5C methyltransferases may function as acid sensors in biological systems.
Keywords: m5C, Acid Sensor, RNA Methyltransferase
