Two DNA sites for MelR in the same orientation are sufficient for optimal MelR-dependent repression at the Escherichia coli melR promoter.
The Escherichia coli melR gene encodes the MelR transcription factor that controls melibiose utilization. Expression of melR is autoregulated by MelR, which represses the melR promoter by binding to a target that overlaps the transcript start. Here, we show that MelR-dependent repression of the melR promoter can be enhanced by the presence of a second single DNA site for MelR located up to 250 base pairs upstream. Parallels with AraC-dependent repression at the araC-araBAD regulatory region and the possibility of the MelR-dependent repression loop formation are discussed. The results show that MelR bound at two distal loci can cooperate together in transcriptional repression.
Biochemistry Department, College of Science, King Saud University, Riyadh, Saudi Arabia.
Mohamed S
MS
Elrobh
Christine L
CL
Webster
Shivanthi
S
Samarasinghe
Danielle
D
Durose
Stephen J W
SJ
Busby
D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008553:Melibiose / Q000378:metabolism; D009876:Operon; D011401:Promoter Regions, Genetic / Q000235:genetics*; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C077649:MelR protein, E coli; D015534:Trans-Activators; D008553:Melibiose