Repression and activation of transcription by Gal and Lac repressors: involvement of alpha subunit of RNA polymerase.
Gal or Lac repressor binding to an upstream DNA segment, in the absence of DNA looping, represses the P1 promoter located on the same face and activates the P2 promoter situated on the opposite face of the DNA helix in the gal operon. Both inhibition and stimulation of transcription requires the physical presence of the C-terminal domain of the alpha subunit of RNA polymerase although the latter is not required for transcription itself. We propose that Gal and Lac repressors inhibit or stimulate transcription initiation by disabling or stimulating RNA polymerase activity at a post-binding step by directly or indirectly altering the C-terminal alpha domain to an unfavorable state at P1 or a more favorable state at P2, respectively.
Choy
H E
HE
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA.
Park
S W
SW
Aki
T
T
Parrack
P
P
Fujita
N
N
Ishihama
A
A
Adhya
S
S
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D056968:Lac Repressors; D046911:Macromolecular Substances; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C050993:Galactose repressor proteins; D056968:Lac Repressors; C539064:LacI protein, E coli; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D012097:Repressor Proteins; D012321:DNA-Directed RNA Polymerases