LrhA positively controls the expression of the locus of enterocyte effacement genes in enterohemorrhagic Escherichia coli by differential regulation of their master regulators PchA and PchB.
Summary Genes essential for eliciting pathogenicity of enterohemorrhagic Escherichia coli are located within the locus of enterocyte effacement (LEE). Expression of LEE genes is positively regulated by paralogues PchA, PchB and PchC, which are encoded by separate loci of the chromosome. To elucidate the underlying regulatory mechanism, we screened transposon mutants exhibiting reduced expression of pchA, transcription level of which is highest among the pch genes. Here, we report that the LysR-homologue A (LrhA) positively regulated the transcription of pchA and pchB. A deletion in lrhA reduced the transcription levels of pchA and pchB to different degrees, and also reduced the expression of LEE-coded type 3-secreted protein, EspB. Expression of LrhA from a plasmid restored and markedly increased the transcription levels of pchA and pchB respectively, and highly induced EspB expression. Deletion analysis of the regulatory region showed that both promoter-proximal (-195 to +88) and promoter-distal (-418 to -392 for pchA and -391 to -375 for pchB) sequences were required for the LrhA-mediated upregulation of pchA and pchB genes. Purified His(6)-LrhA protein differentially bound to the regulatory regions of pchA/B, suggesting that direct regulation of pchA and pchB genes by LrhA in turn controls the expression of LEE genes.
Honda
Naoko
N
Department of Bacteriology, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640, Japan.
Iyoda
Sunao
S
Yamamoto
Shouji
S
Terajima
Jun
J
Watanabe
Haruo
H
D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000378:metabolism; D054324:Enterohemorrhagic Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D016254:Mutagenesis, Insertional; D010750:Phosphoproteins / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D037521:Virulence Factors / Q000096:biosynthesis*
D001425:Bacterial Outer Membrane Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; C087863:EaeB protein, E coli; D029968:Escherichia coli Proteins; C457340:LEE protein, E coli; C490682:LrhA protein, E coli; D010750:Phosphoproteins; D014157:Transcription Factors; D037521:Virulence Factors