MULTIPLE NOVEL PROMOTERS FROM THE EARLY REGION IN THE STREPTOMYCES TEMPERATE PHAGE PHI-C31 ARE ACTIVATED DURING LYTIC DEVELOPMENT

Evidence is presented that transcription of most of the early genes in the Streptomyces coelicolor A3(2) phage phiC31 is from a series of un usual promoters that depend on a function expressed early in the phiC3 1 lytic cycle. Primer extension analysis on the 5' ends of three early mRNAs, from samples prepared 10 min after induction of a thermosensit ive phiC31 lysogen, showed that the 5' ends all mapped close to highly similar sequences, which are proposed to be an important part of phag e-specific promoters. In a shotgun cloning experiment, a fragment cont aining one of these sequences strongly activated transcription of the xylE reporter gene in plaques of a phiC31-derived promoter-probe vecto r. Another of the sequences was inserted into a xylE-containing promot er-probe plasmid vector, and promoted xylE expression only when the ho st was supporting the lytic cycle of phiC31. This suggested that a tra nscription factor needed for activity of the promoters was present onl y in phiC31-infected cells. Examination of published and unpublished p hiC31 sequence data revealed several more sequences that closely resem ble the conserved region of the characterized promoters. Most of these are found in positions close to apparent transcription start sites ma pped previously by low-resolution S1 mapping. An overall consensus seq uence for the conserved region suggests a general organization (though not a primary sequence) resembling that of promoters recognized in ot her bacteria by the sigma54 form of RNA polymerase.