Activation of phenoxazinone synthase expression in Streptomyces lividans: characterization of the activator fragment from Streptomyces antibioticus.

We have isolated an active 719 bp fragment from the 4.3 kb region of the genome of Streptomyces antibioticus that activates a silent phenoxazinone synthase (PHS) gene in Streptomyces lividans. Sequencing of the 719 bp fragment revealed several potential open reading frames (ORFs); however, the distribution of G + C in these putative ORFs was uncharacteristic of streptomycete genes. No RNA products transcribed from the active sequence were detected by dot-blot hybridization and no proteins corresponding in size to the predicted products from the ORFs were observed when appropriate plasmids were used as templates in a streptomycete coupled transcription-translation system. Fragments of 249 and 243 bp, respectively, were obtained from the 719 bp fragment from S. antibioticus and from the S. lividans genome by PCR cloning. Both fragments activated phs in S. lividans when cloned on a high copy number plasmid.