Repression of deoP2 in Escherichia coli by CytR: conversion of a transcription activator into a repressor.
In the deoP2 promoter of Escherichia coli, a transcription activator, cAMP-CRP, binds at two sites, centered at -41.5 and -93.5 from the start site of transcription, while a repressor, CytR, binds to a space between the two cAMP-CRP complexes. The mechanisms for the cAMP-CRP-mediated transcription activation and CytR-mediated transcription repression were investigated in vitro using purified components. We classified the deoP2 promoter as a class II cAMP-CRP-dependent promoter, primarily by the action of cAMP-CRP at the downstream site. Interestingly, we also found that deoP2 carries an "UP-element" immediately upstream of the downstream cAMP-CRP site. The UP-element overlaps with the DNA site for CytR. However, it was observed that CytR functions with the RNA polymerase devoid of the C-terminal domain of the alpha-subunit as well as with intact RNA polymerase. The mechanism of repression by CytR proposed in this study is that the cAMP-CRP bound at -41.5 undergoes an allosteric change upon direct interaction with CytR such that it no longer maintains a productive interaction with the N-terminal domain of alpha, but instead acts as a repressor to interfere with RNA polymerase acting on deoP2.
Shin
M
M
Department of Microbiology, Chonnam University Medical College, 5 Hakdong, Dongku, Gwangju, South Korea 501-714.
Kang
S
S
Hyun
S J
SJ
Fujita
N
N
Ishihama
A
A
Valentin-Hansen
P
P
Choy
H E
HE
D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008957:Models, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012097:Repressor Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*
D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; C048425:CytR protein, E coli; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D015534:Trans-Activators