DNA Methylation


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YhdJ, a non-essential CcrM-like DNA methyltransferase of Escherichia coli and Salmonella enterica

Reference: Broadbent,S.E., Balbontin, R., Casadesus, J., Marinus, M.G. and van der Woude, M. (2007)  YhdJ, a non-essential CcrM-like DNA methyltransferase of Escherichia coli and Salmonella enterica. J. Bacteriol. in press

The Caulobacter crescentus DNA adenine methyltransferase CcrM and its homologs in alpha-Proteobacteria are essential for viability. CcrM is 34% identical to the yhdJ gene products of Escherichia coli and Salmonella enterica. This study provides evidence that the E. coli yhdJ gene encodes a DNA adenine methyltransferase. In contrast to an earlier report, however, we show that yhdJ is not an essential gene in either E. coli or in S. enterica.


Increased adherence and actin pedestal formation by dam-deficient enterohemorrhagic Escherichia coli O157:H7

Reference: Campellone, K.G., Roe,  A.J., Løbner-Olesen
, A., Murphy, K.C., Magoun, L., Brady, M.J., Donohue-Rolfe, A.J., Tzipori, S., Gally, D.L., Leong, J.M. and Marinus, M. G. (2007) Increased adherence and actin pedestal formation by dam-deficient enterohemorrhagic Escherichia coli O157:H7. Molec. Microbiol. 63, 1468-1481.



DNA methylation reviews

Reference:
Løbner-Olesen, A., Skovgaard, O. and Marinus, M.G. (2005) Dam methylation: coordinating cellular processes. Current Opinion in Microbiology 8, 154-160.

Reference: Marinus, M.G. (2004) DNA Modification: Eubacterial GATC methyltransferase, in Encyclopedia of Biological Chemistry, Elsevier/Academic Press, San Diego.



Regulated expression of the Escherichia coli dam gene

Reference: Calmann, M.A. and Marinus, M.G. (2003) Regulated expression of the Escherichia coli dam gene. J. Bacteriology 185, 5012-5014.

Regulated expression of the Escherichia coli dam gene has been achieved with the araBAD promoter lacking a ribosome binding site. Cultures of dam mutants containing plasmid pMQ430 show no detectable methylation in the absence of arabinose and complete methylation in its presence. Dam methyltransferase is a substrate for the Lon protease.


Role of SeqA and Dam in Escherichia coli gene expression

Reference:
Løbner-Olesen, A., Marinus, M.G. and Hansen, F.G. (2003) Role of SeqA and Dam in Escherichia coli gene expression- a global/microarray analysis. Proc. Natl. Acad. Sci. USA 100, 4672-4677.

High-density oligonucleotide arrays were used to monitor global transcription patterns in Escherichia coli with various levels of Dam and SeqA proteins. Cells lacking Dam methyltransferase showed a modest increase in transcription of the genes belonging to the SOS regulon. Bacteria devoid of the SeqA protein, which preferentially binds hemimethylated DNA, were found to have a transcriptional profile almost identical to WT bacteria overexpressing Dam methyltransferase. The latter two strains differed from WT in two ways. First, the origin proximal genes were transcribed with increased frequency due to increased gene dosage. Second, chromosomal domains of high transcriptional activity alternate with regions of low activity, and our results indicate that the activity in each domain is modulated in the same way by SeqA deficiency or Dam overproduction. We suggest that the methylation status of the cell is an important factor in forming and/or maintaining chromosome structure.

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