Four T7 RNA polymerase promoters contain an identical 23 bp sequence

The DNA sequences of four promoters for the bacteriophage-specified T7 RNA polymerase have been determined. All four regions contain an identical 23 bp sequence 5' pTAATACGACTCACTATAGGGAG-A(oh) which includes the 17 bp prior to and the first 6 bp of the transcribed region. They are located at 46.5, 55, 57 and 87% on the standard T7 map, thereby corresponding to the in vitro T7 class III RNA species IIIa, IV, V and IIIb, respectively. The precise RNA initiation sites were determined by 5' terminal RNA sequence analysis of the transcripts synthesized from promoter-containing DNA fragments. The comparative properties of these promoters for the monomeric T7 RNA polymerase and those for the multimeric E. coli RNA polymerase are discussed.