[Phage T7 RNA-polymerase: gene cloning and its structure]

Gene 1.0 to T7 phage coding for a phage-specific RNA polymerase has been cloned in a plasmid vector. One of the clones obtained, viz. E. coli K12 HB101 (pSK-T7-1.0a), produced an active T7 RNA polymerase as revealed by the fact that its extract stimulated RNA synthesis on the T7 DNA template in the presence of rifampicin. Analysis of gene 1.0 fragments isolated from pSK-T7-1.0a plasmid made it possible to refine the sequence of this gene which has been recently published by the authors of the present paper and, independently, by other workers. Another plasmid, pSK-T7-1.0b, did not differ from pSK-T7-1.0a in the restriction map. However, it failed to induce production of a rifampicin-insensitive RNA polymerase. Sequencing revealed a deletion of one T residue in gene 1.0 present in this plasmid.