A CRYPTIC PROMOTER IN THE OR REGION OF BACTERIOPHAGE-LAMBDA

作者：WOODY ST; FONG RSC; GUSSIN GN

来源：Journal of Bacteriology, 1993, 175(17): 5648-5654.

A cryptic promoter, designated P(alpha), initiates transcription within the O(R) region of bacteriophage lambda. Transcription from P(alpha) proceeds in the direction of the cl repressor gene from sites 46 and 48 bp preceding the P(RM) transcription start site. P(alpha) is likely to compete with both P(R) and P(RM) for formation of open complexes, since it is only active when P(R) is mutated and can be suppressed by mutations that increase P(RM) activity. In addition, transcription initiation at P(alpha) is blocked by lambda repressor. Kinetic analysis of relative abundance of the products of in vitro transcription indicated that P(alpha) was approximately 113 as strong as P(RM). However, a P(alpha)- mutation had little effect on K(B)k(f) (the association rate constant) for P(RM). These observations can be explained by the finding that open complexes formed at P(alpha) are relatively unstable (half-life = 20 to 25 min). Dissociation of RNA polymerase from P(alpha) allows additional open complexes to form at P(R) or P(RM), and thus the apparent strength of P(alpha) decreases with increasing preincubation times.