Structure of a promoter for T7 RNA polymerase.

We have determined the nucleotide sequence of a Hpa II restriction fragment of the phage T7 DNA containing a promoter for the phage-specified RNA polymerase. (Hpa II is a restriction endonuclease from Haemophilus parainfluenzae.) Mapping of the Hpa II restriction fragments on the T7 genome shows this promoter to be the second of tandem promoters separated by approximately 170 base pairs that begin transcription by the T7 RNA polymerase at approximately 15% of the genome. Features of the sequence involved in recognition by the T7 RNA polymerase are discussed and include the following region of hyphenated 2-fold symmetry (boxed regions are related through a 2-fold axis of symmetry at the center of the sequence shown). (See article). This sequence includes the initiation site, since the message transcribed from this fragment begins pppG-G-G-A. Combination of our results with work of others has permitted this fragment to be mapped at the junction of T7 genes 1 and 1.1. The RNA transcribed from this fragment begins within gene 1 and contains the RNase III cleavage site that lies between genes 1 and 1.1. This sequence is compared to other processing sites in T7 early message.