Separate contributions of UhpA and CAP to activation of transcription of the uhpT promoter of Escherichia coli.
Activation of promoters by multiple transcription factors might occur through favorable contacts of the activators with themselves or RNA polymerase, or by changes in DNA geometry that enhance formation of the transcription complex. Transcription of the Escherichia coli uhpT gene, encoding the organophosphate transporter, requires the response regulator UhpA and is stimulated by the global regulator protein CAP. CAP binds to the uhpT promoter at a single site, centered at -103.5 bp relative to the start of transcription, and UhpA binds to multiple sites between positions -80 and -32. Overexpression of UhpA did not reduce the degree of CAP stimulation of uhpT-lacZ expression, showing that CAP action is more complex than enhancement of the binding of UhpA. Footprinting experiments demonstrated that UhpA and CAP modestly stimulated each other's binding to the uhpT promoter, but did not affect the positioning of the binding sites. An in vitro transcription system was used to examine the contribution of each transcription factor at the uhpT promoter. Action of UhpA and CAP proteins was not affected by template supercoiling. Kinetic analyses of productive and abortive initiation showed that CAP acted both to stabilize by fivefold the open promoter complexes formed in the presence of UhpA and to enhance by twofold the rate of their formation. These results indicate that open complex formation requires UhpA and that CAP stabilizes the open complex.
Olekhnovich
I N
IN
Department of Microbiology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Dahl
J L
JL
Kadner
R J
RJ
D000495:Allosteric Site; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D000242:Cyclic AMP / Q000494:pharmacology; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D018983:DNA Footprinting; D004278:DNA, Superhelical / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D020035:Holoenzymes / Q000378:metabolism; D007700:Kinetics; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D013698:Templates, Genetic; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D015533:Transcriptional Activation / Q000187:drug effects
D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D020035:Holoenzymes; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C489848:UhpA protein, E coli; C063498:UhpT protein, E coli; C080370:UhpA protein, Bacteria; D004247:DNA; D000242:Cyclic AMP; D012321:DNA-Directed RNA Polymerases; D003850:Deoxyribonuclease I