The Nine Genes of the Nocardia lactamdurans Cephamycin Cluster Are Transcribed into Large mRNAs from Three Promoters, Two of Them Located in a Bidirectional Promoter Region

Abstract

ABSTRACT The nine biosynthesis genes of the Nocardia lactamdurans cephamycin cluster are expressed as three different mRNAs initiating at promoters latp , cefDp , and pcbABp , as shown by low-resolution S1 nuclease protection assays and Northern blotting analysis. Bidirectional expression occurred from divergent promoters ( latp and cefDp ) located in a 629-bp intergenic region that contains three heptameric direct repeats similar to those recognized by members of the SARP ( Streptomyces antibiotic regulatory proteins) family. The lat gene is transcribed in a single monocistronic transcript initiating at latp . A second unusually long polycistronic mRNA (more than 16 kb) corresponding to six biosynthesis genes ( pcbAB , pcbC , cmcI , cmcJ , cefF , and cmcH ) started at pcbABp . A third polycistronic mRNA corresponding to the cefD and cefE genes started at cefDp .