Activation of the leu-500 promoter by adjacent transcription
Open Access
- 1 February 1994
- journal article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 176 (4), 1077-1086
- https://doi.org/10.1128/jb.176.4.1077-1086.1994
Abstract
The leu-500 mutation is an A-to-G point mutation in the -10 region of the promoter controlling the leuABCD operon of Salmonella typhimurium. Suppression of the leu-500 mutation in an S. typhimurium topA mutant has demonstrated the functional dependency of this mutated promoter on negative supercoiling. A plasmid bearing a minimal leu-500 promoter region (positions -80 to +87) failed to restore its expression in the S. typhimurium topA mutant. We showed that transcription-mediated local negative supercoiling can activate the leu-500 promoter on a plasmid. The coupled transcription and translation process is required for this activation, but peptide-mediated membrane anchorage may not be involved in this activation. Although the effect of negative supercoiling generated during transcription away from the promoter is limited to a short distance of 250 bp, it can activate the negative-supercoiling-dependent leu-500 promoter from positions either 5' or 3' of the leu-500 promoter. In the presence of a parallel-oriented lac promoter which transcribed away from the 3' end of the leu-500 promoter, transcriptional activation of the leu-500 promoter is a strong indication of cooperativity during the transcriptional initiation process.Keywords
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