Alteration in the '- 10' sequence of the A2 promoter of bacteriophage T7 reduces the rate of transcription initation

The rate of transcription initiation, in the absence of other factors, is determined by intrinsic properties of the promoter. This largely depends on the DNA structure at the promoter region. The A2 promoter of bacteriophage T7 is an early promoter, specific for the RNA polymerase of the host E.coli. It is also one of the strongest promoters tested so far in vitro. We show here that a mutation in the '-10' region of T7A2 only reduces the strength of the promoter: transcription driven by the mutuant promoter results in much less product. The site of intiation is the same as that in the wild-type promoter