Transcription during the development of bacteriophage phi29: definition of "early" and "late" phi29 ribonucleic acid.

Bacteriophage phi29 messenger ribonucleic acid (mRNA) production following infection of Bacillus subtilis has been analyzed. Early (e) phi29 RNA, made prior to the onset of phage deoxyribonucleic acid (DNA) replication and exclusively from the light (L) phi29 DNA strand, has been shown by RNA-DNA hybridization-competition experiments to be present throughout the phage latent period. No repression of e RNA production during phi29 development could be demonstrated. Unmodified host RNA polymerase molecules appear to be sufficient for the synthesis of e RNA since phage-specific RNA made in the presence of chloramphenicol hybridizes only to the L strand of phi29 DNA, and this RNA can be effectively competed during hybridization by e RNA. The appearance of late (l) phi29 RNA is coincident with the onset of viral DNA replication. This RNA consists of L DNA strand transcripts which are identical to e RNA and a new class of mRNAs made exclusively from the "heavy" (H) phi29 DNA strand (lH). Protein synthesis in infected cells is required for lH RNA production. Studies with the antibiotic rifamycin demonstrated that synthesis of the major phi29 structural proteins is dependent on production of lH RNA.