TRANSCRIPTION REGULATION IN BACILLUS-SUBTILIS PHAGE PHI-29 - EXPRESSION OF THE VIRAL PROMOTERS THROUGHOUT THE INFECTION CYCLE

Transcription of the genome of Bacillus subtilis phage Phi 29 is tight ly controlled, taking place in two stages, early and late. We have ana lyzed the abundance of the transcripts produced from each viral promot er throughout the infection cycle. We compare the relative strength of each promoter, as well as get a better understanding of the regulator y events, finding a new promoter regulated by the viral protein p4. Th e two strong early promoters, A2b and A2c, responsible for the express ion of genes 6 to 1, are coordinately repressed by the viral protein p 4, although repression is not complete: both promoters are still activ e at late times of infection. Since repression by protein p4 was very efficient in vitro, and affects its own synthesis, it is likely that t his protein is produced in limiting amounts, not being bound to all vi ral DNA molecules present in the cell at a given time. Protein p4, als o known to activate the late promoter responsible for the expression o f all the structural and morphogenetic genes, is the key regulator of phage Phi 29 development. (C) 1995 Academic Press, Inc.