Lactose promoter mutation Pr115 activates an overlapping promoter within the lactose control region.
The Escherichia coli lac promoter mutation Pr115, an A X T to T X A transversion at +1 (the transcription initiation site of the lac wild-type and lac UV5 promoters), creates a new "-10 region"-like sequence starting at +1. We show that this mutation activates a new RNA polymerase binding site (P115) that overlaps with, and is shifted 12 base-pairs downstream from, the wild-type RNA polymerase binding site (P1). Nuclease S1 mapping studies and RNA polymerase protection experiments in vitro indicate that, in the absence of CAP-cAMP, this new site is used preferentially over the P1 site. In vivo, beta-galactosidase assays of the Pr115 mutation in combination with mutations of the P1 "-35 region" demonstrate that the P1 -35 region sequences are not involved in the interaction between RNA polymerase and P115 in the absence of CAP-cAMP; therefore P115 is an independent binding site. The presence of CAP-cAMP in vivo stimulates polymerase binding and initiation at P1, which serves to block polymerase from binding at P115.
M L
ML
Peterson
W S
WS
Reznikoff
D001483:Base Sequence; D000242:Cyclic AMP / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D007763:Lac Operon; D009154:Mutation; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000378:metabolism; D011953:Receptors, Cyclic AMP / Q000378:metabolism; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis
D012329:RNA, Bacterial; D011953:Receptors, Cyclic AMP; D000242:Cyclic AMP; D012321:DNA-Directed RNA Polymerases; D001616:beta-Galactosidase