Structure of a promoter for T7 RNA polymerase.

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Abstract
The nucleotide sequence of a Hpa II restriction fragment of the phage T7 DNA containing a promoter for the phage-specified RNA polymerase was determined. (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 2nd of tandem promoters separated by .apprx. 170 base pairs that begin transcription by the T7 RNA polymerase at .apprx. 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). .**GRAPHIC**. This sequence includes the initiation site, since the message transcribed from this fragment begins pppG-G-G-A. This and other results 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.