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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