Regulation of <i>traJ</i> transcription in the Salmonella virulence plasmid by strand‐specific DNA adenine hemimethylation

Camacho, Eva María; Casadesús, Josep

doi:10.1111/j.1365-2958.2005.04788.x

Cited by 69 publications

(51 citation statements)

References 82 publications

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“…If these observations faithfully reproduce the scenario of a replicating plasmid, passage of the replication fork will permit Lrp binding to one daughter DNA molecule but not to the other, and traJ activation will occur in only one of the newly replicated plasmids. Electrophoretic migration of free, unbound traJ DNA is also (46). A single methyl group is able to induce structural changes in a DNA fragment (72).…”

Section: Derepression Of Tra In a Dammentioning

confidence: 98%

“…In pSLT, Dam methylation does not act directly on the tra operon but acts on the regulatory genes traJ and finP (45,255). Transcription of traJ, which encodes a transcriptional activator of tra, is repressed by Dam methylation (46). In turn, transcription of finP, which encodes a small RNA that antagonizes TraJ expression, is activated by Dam methylation (46,255).…”

Section: Derepression Of Tra In a Dammentioning

confidence: 99%

“…Transcription of traJ, which encodes a transcriptional activator of tra, is repressed by Dam methylation (46). In turn, transcription of finP, which encodes a small RNA that antagonizes TraJ expression, is activated by Dam methylation (46,255). This dual effect of Dam methylation accounts for the increase in tra operon expression observed in Dam Ϫ donors (48).…”

Section: Derepression Of Tra In a Dammentioning

confidence: 99%

“…If the above model is correct, Lrp-mediated activation of traJ transcription will be restricted to one hemimethylated daughter plasmid molecule (46). This epigenetic switch may be viewed as a mechanism to limit TraJ synthesis and hence to restrain activation of conjugal transfer.…”

Section: Derepression Of Tra In a Dammentioning

confidence: 99%

“…Footprint analysis also shows that methylation of the LRP-2 GATC alters the distribution of DNase I-hypersensitive sites in the traJ UAS, providing further evidence that Lrp binding follows different patterns depending on the methylation state of the LRP-2 GATC (46). Lrp can also bind a hemimethylated traJ UAS (see below), suggesting that Dam methylation may serve as a sensor of plasmid replication: traJ transcription will be repressed in a nonreplicating plasmid, but repression will be lifted during the transient hemimethylation lapse that follows passage of the replication fork (46).…”

Section: Derepression Of Tra In a Dammentioning

confidence: 99%

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Epigenetic Gene Regulation in the Bacterial World

Casadesús

Low

2006

Microbiol Mol Biol Rev

568

562

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SUMMARY Like many eukaryotes, bacteria make widespread use of postreplicative DNA methylation for the epigenetic control of DNA-protein interactions. Unlike eukaryotes, however, bacteria use DNA adenine methylation (rather than DNA cytosine methylation) as an epigenetic signal. DNA adenine methylation plays roles in the virulence of diverse pathogens of humans and livestock animals, including pathogenic Escherichia coli, Salmonella, Vibrio, Yersinia, Haemophilus, and Brucella. In Alphaproteobacteria, methylation of adenine at GANTC sites by the CcrM methylase regulates the cell cycle and couples gene transcription to DNA replication. In Gammaproteobacteria, adenine methylation at GATC sites by the Dam methylase provides signals for DNA replication, chromosome segregation, mismatch repair, packaging of bacteriophage genomes, transposase activity, and regulation of gene expression. Transcriptional repression by Dam methylation appears to be more common than transcriptional activation. Certain promoters are active only during the hemimethylation interval that follows DNA replication; repression is restored when the newly synthesized DNA strand is methylated. In the E. coli genome, however, methylation of specific GATC sites can be blocked by cognate DNA binding proteins. Blockage of GATC methylation beyond cell division permits transmission of DNA methylation patterns to daughter cells and can give rise to distinct epigenetic states, each propagated by a positive feedback loop. Switching between alternative DNA methylation patterns can split clonal bacterial populations into epigenetic lineages in a manner reminiscent of eukaryotic cell differentiation. Inheritance of self-propagating DNA methylation patterns governs phase variation in the E. coli pap operon, the agn43 gene, and other loci encoding virulence-related cell surface functions.

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Section: Derepression Of Tra In a Dammentioning

confidence: 98%