Superimposition of tyrR protein-mediated regulation on osmoresponsive transcription of Escherichia coli proU in vivo.
Osmotic regulation of proU expression in the enterobacteria is achieved, at least in part, by a repression mechanism involving the histone-like nucleoid protein H-NS. By the creation of binding sites for the TyrR regulator protein in the vicinity of the sigma70-controlled promoter of proU in Escherichia coli, we were able to demonstrate a superposed TyrR-mediated activation by L-phenylalanine (Phe), as well as repression by L-tyrosine, of proU expression in vivo. Based on the facts that pronounced activation in the presence of Phe was observed even at a low osmolarity and that the affinity of binding of TyrR to its cognate sites on DNA is not affected by Phe, we argue that H-NS-mediated repression of proU at a low osmolarity may not involve a classical silencing mechanism. Our data also suggest the involvement of recruited RNA polymerase in the mechanism of antirepression in E. coli.
Gowrishankar
J
J
Centre for Cellular & Molecular Biology, Hyderabad 500007, India. shankar@ccmb.ap.nic.in
Pittard
A J
AJ
D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D009994:Osmolar Concentration; D010649:Phenylalanine / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; C060774:ProU protein, Bacteria; D012097:Repressor Proteins; D014157:Transcription Factors; C069256:TyrR protein, E coli; D010649:Phenylalanine