Competitive interaction of the OxyR DNA‐binding protein and the Dam methylase at the antigen 43 gene regulatory region in Escherichia coli

Abstract

SummaryThe antigen 43 surface protein of Escherichia coli is expressed in a phase-variable manner by a mechanism involving alternative activation and repression of transcription of the agn43 gene. The repressor is the OxyR DNA-binding protein, and its binding site was found to be located downstream of the agn43 transcription start site in a region of DNA that encompasses three 5¢-GATC-3¢ sequences that are subject to Dam-mediated DNA methylation. It has been suggested previously that the phase-variable expression of antigen 43 results from a competition between Dam methylase and the OxyR repressor for these sites. The 5¢-GATC-3¢ sequences were inactivated for methylation by site-directed mutagenesis, and all possible combinations of inactive and active sites were assessed for effects on phase-variable expression of the agn43 gene. Inactivation of any 5¢-GATC-3¢ site individually had no effect; at least two sites had to be inactivated to disrupt the normal pattern of expression. Studies of OxyR interaction with agn43 DNA showed that methylation of any two 5¢-GATC-3¢ sites was necessary and sufficient to block binding of the repressor. It was also found that the adenines of the second and third 5¢-GATC-3¢ sites are required for OxyR binding, demonstrating that the sites for Dam methylation and for repressor binding are intimately associated. This is consistent with a competition model in which Dam and OxyR share a preference for specific DNA sequences in the regulatory region of the agn43 gene. IntroductionThe ability of bacteria to colonize and to cause infection

Genomics of DNA cytosine methylation in Escherichia coli reveals its role in stationary phase transcription

“…Cytosine methylation is a key regulator of gene expression in mammals, with major influence on processes such as development and cancer progression. In bacteria, however, DNA adenine methylation has been recognized as a regulator of gene expression, primarily by influencing the activities of transcription factors whose effects are correlated with the target's methylation status 14,15 . However, until very recently 27 when cytosine methylation was shown to regulate ribosomal gene expression in stationary phase, no role for cytosine methylation in gene expression control had been documented for bacteria, at least for enterobacteria.…”

“…The beststudied solitary methyltransferase in E. coli is DNA adenine methyltransferase, which targets the G m ATC motif 13 . This methyl mark has important roles in regulating on-off gene expression by influencing the binding properties of transcription factors to DNA sites containing the methylated motif 14,15 ; it also influences replication by regulating the recruitment of the initiator of replication to the origin of replication 16,17 and regulates DNA repair by informing the methyl-directed mismatch repair system about the age of the DNA strand [18][19][20] . Another well-studied adenine methyltransferase is CcrM in Caulobacter crescentus, which methylates the GANTC site and acts as a cell cycle regulator 21 .…”

Antigen-43-mediated autoaggregation impairs motility in Escherichia coli

“…The a subunit, on the other hand, remains attached to the bacterial cell surface via interactions with the b subunit (Henderson et al, 2004). The expression of Ag43 is phase-variable with switching rates of~10 23 per cell per generation due to the concerted actions of Dam methylase (positive regulation) and OxyR (negative regulation) (Henderson & Owen, 1999;Schembri et al, 2003a;Waldron et al, 2002).…”

“…The a subunit, on the other hand, remains attached to the bacterial cell surface via interactions with the b subunit (Henderson et al, 2004). The expression of Ag43 is phase-variable with switching rates of~10 23 per cell per generation due to the concerted actions of Dam methylase (positive regulation) and OxyR (negative regulation) (Henderson & Owen, 1999;Schembri et al, 2003a;Waldron et al, 2002).Ag43 dramatically enhances biofilm formation (Danese et al, 2000;Kjaergaard et al, 2000b; Reisner et al, 2003) and is specifically correlated with the biofilm mode of growth (Schembri et al, 2003b). Recent work has demonstrated that Ag43 expression is correlated with biofilm formation by uropathogenic E. coli during infection of bladder cells (Anderson et al, 2003) and in enteropathogenic E. coli (Torres et al, 2002).…”

Differential Expression of the Escherichia coli Autoaggregation Factor Antigen 43

“…The flu promoter region contains three GATC sites, which overlap a recognition sequence for OxyR (9,10,13). When the GATC sites are methylated, OxyR cannot bind; conversely, bound OxyR prevents methylation (29).…”