Activation of the leu-500 promoter by adjacent transcription.
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.
Tan
J
J
Department of Pharmacology, School of Medicine, Wayne State University, Detroit, Michigan 48201.
Shu
L
L
Wu
H Y
HY
D001483:Base Sequence; D004264:DNA Topoisomerases, Type I / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D007763:Lac Operon / Q000235:genetics; D007930:Leucine / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D009876:Operon / Q000235:genetics*; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014176:Protein Biosynthesis; D012486:Salmonella typhimurium / Q000235:genetics*; D013489:Suppression, Genetic; D014158:Transcription, Genetic
D004264:DNA Topoisomerases, Type I; D007930:Leucine