Global transcription pattern of phi C31 after induction of a Streptomyces coelicolor lysogen at different growth stages.

Using two complementary strategies for low-resolution S1 mapping, the global pattern of phi C31 transcription was studied after induction of thermoinducible phi C31 lysogens of Streptomyces coelicolor A3(2). A complex pattern of early transcripts was seen, with a peak of abundance at about 10 min post-induction. Nearly all of these transcripts were from DNA located to the right of the c (repressor) gene and to the left of the attP site: a region of about 14 kb. Early transcription was also observed immediately to the left of the c gene. The c gene itself was also induced, with an earlier expression peak (about 5 min post-induction). Primary late transcripts were generally relatively long, but degraded. They apparently corresponded to most of the 18 kb region to the left of the c gene. Some shorter and more persistent late transcripts corresponded to DNA close to or overlapping the cos site. Large late transcripts from a region close to the left-hand end of the phi C31 genome showed evidence of processing to more stable, smaller RNA species. A failure of older cultures (more than 12 h old) to be induced productively was correlated with a much longer period of early transcription, reduced late transcription, failure to synthesize a major virion protein, and failure to package phi C31 DNA. Moreover, heat treatment of the older lysogenic cultures did not result in the phi C31-dependent shut-down of host rRNA transcription previously observed for young cultures (Rodríguez et al., Journal of General Microbiology (1986) 132, 1695-1701; Clayton & Bibb, Molecular Microbiology (1990) 4, 2179-2185).