title: The role of upstream sequences in determining the strength of an rRNA promoter of E. coli.
abstract: In vitro transcription experiments were carried out with recombinant plasmids containing the promoters of the rrnB gene of Escherichia coli, and with deletion mutants lacking various lengths of the AT-rich sequence upstream from the P1 promoter of that gene. The main conclusions are as follows: The in vitro transcriptional activity of the P1 and P2 promoters of the rrnB gene are an order of magnitude higher on closed-circular (supercoiled) templates than on linear DNA; the strong P1 and P2 promoters are heparin-sensitive on linear templates, and on circular DNA only P2 is heparin-resistant; removal of the upstream AT-rich region did not decrease the apparent in vitro strength of the P1 promoter under standard conditions (50 mM KCl, high RNA polymerase/DNA ratio); at higher salt concentrations, or with a lower RNA polymerase/DNA ratio, the deletion mutants displayed much lower in vitro transcriptional activity than the wild-type, and the apparent weakening of the P1 promoter was roughly proportional to the length of the deleted AT-rich sequence. The implications of these findings for the possible in vivo role of the AT-rich region are discussed.
mesh_terms: D001483:Base Sequence; D002872:Chromosome Deletion; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D005786:Gene Expression Regulation; D008040:Genetic Linkage; D011401:Promoter Regions, Genetic; D012335:RNA, Ribosomal / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012335:RNA, Ribosomal