The anti-initial transcribed sequence, a portable sequence that impedes promoter escape, requires sigma70 for function.
The anti-sequence, a portable element extending from +1 to +15 of the transcript, is sufficient to prevent promoter escape from a variety of strong final sigma70 promoters. We show here that this sequence does not function with even the strongest final sigma32 promoter. Moreover, a particular class of substitutions in final sigma70 that disrupt interaction between Region 2.2 of final sigma70 and a coiled-coiled motif in the beta'-subunit of RNA polymerase antagonizes the function of the anti-element. This same group of mutants prevents lambdaQ-mediated anti-termination at the lambdaP(R') promoter. At this promoter, interaction of final sigma70 with the non-template strand of the initial transcribed sequence (ITS) is required to promote the pause prerequisite for anti-termination. These mutants prevent pausing because they are defective in this recognition event. By analogy, we suggest that interaction of final sigma70 with the non-template strand of the anti-ITS is required for function of this portable element, thus explaining why neither final sigma32 nor the Region 2.2 final sigma70 mutants mediate anti-function. Support for the analogy with the lambdaP(R') promoter comes from preliminary experiments suggesting that the anti-ITS, like the lambdaP(R') ITS, is bipartite.
Chan
C L
CL
Department of Stomatology, University of California, San Francisco, 94143, USA.
Gross
C A
CA
D001483:Base Sequence; D004247:DNA; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013698:Templates, Genetic
D012333:RNA, Messenger; D012808:Sigma Factor; D004247:DNA; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases