Journal
FEMS MICROBIOLOGY LETTERS
Volume 328, Issue 1, Pages 78-85Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1574-6968.2011.02482.x
Keywords
Escherichia coli; 5-methylcytosine; dcm; LC MS; MS
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Funding
- Geneseo Foundation
- NIH [R15AI074035-01]
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In Escherichia coli, cytosine DNA methylation is catalyzed by the DNA cytosine methyltransferase (Dcm) protein and occurs at the second cytosine in the sequence 5'CCWGG3'. Although the presence of cytosine DNA methylation was reported over 35years ago, the biological role of 5-methylcytosine in E.coli remains unclear. To gain insight into the role of cytosine DNA methylation in E.coli, we (1) screened the 72 strains of the ECOR collection and 90 recently isolated environmental samples for the presence of the full-length dcm gene using the polymerase chain reaction; (2) examined the same strains for the presence of 5-methylcytosine at 5'CCWGG3' sites using a restriction enzyme isoschizomer digestion assay; and (3) quantified the levels of 5-methyl-2'-deoxycytidine in selected strains using liquid chromatography tandem mass spectrometry. Dcm-mediated cytosine DNA methylation is conserved in all 162 strains examined, and the level of 5-methylcytosine ranges from 0.86% to 1.30% of the cytosines. We also demonstrate that Dcm reduces the expression of ribosomal protein genes during stationary phase, and this may explain the highly conserved nature of this DNA modification pathway.
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