MODEL PROKARYOTIC PROMOTER - VI - CONSTRUCTS WITH OVERLAPPING CONSENSUS PROMOTERS

Overlapping promoter signals were constructed with three copies of Pri bnow box and in adjacent repeats of the -35 consensus hexanucleotides (TTGACA) or ''random'' sequences of the plasmid vector. These construc ts were assessed for interaction with E. coli RNA polymerase in vitro and iii vivo. III vivo transcription start mapping by primer extension and permanganate footprinting of open complexes show that the choice of promoter by RNA polymerase depends on the conformity of the -35 reg ion to the consensus. The position of the transcription start is influ enced not only by the Pribnow box but also by the DNA structure at thi s region. Permanganate modification patterns in vivo with and without rifampicin indicate that the polymerase is halted at the Pribnow box i n open or initiation and early elongation complexes.