Cloning and characterization of mycobacteriophage I3 promoters

Restriction fragments of mycobacteriophage I3 DNA capable of initiating transcription have been cloned into a promoter selection vector of Escherichia coli, and selected on the basis of development of resistance to chloramphenicol. The growth pattern of these 'promoter clones' on a concentration gradient of chloramphenicol and the biochemical assays of the chloramphenicol acetyl transferase have permitted the assessment of their relative promoter strengths. DNA sequence analysis revealed significant homology of these promoters to the -35 regions of the mycobacterial--and E. coli promoter consensus, but less so the -10 region. Based on the sequence of phage I3 promoters identified here and the reported sequences of mycobacterial promoters, a promoter consensus for mycobacteria has been generated.