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Transcription during the development of bacteriophage phi29: definition of "early" and "late" phi29 ribonucleic acid
Abstract:
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.
Insights
Bacteriophage phi29 RNA production involves early (e) RNA synthesis from the light DNA strand, continuing throughout infection. Late (l) RNA, including heavy strand transcripts (lH), appears with DNA replication and is essential for producing viral structural proteins.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage phi29 infects Bacillus subtilis, utilizing host machinery for replication.
- Understanding phage gene expression is crucial for deciphering viral life cycles.
Purpose of the Study:
- To analyze messenger ribonucleic acid (mRNA) production during Bacillus subtilis infection by bacteriophage phi29.
- To characterize the temporal appearance and regulatory mechanisms of early (e) and late (l) phi29 RNA.
Main Methods:
- RNA-DNA hybridization-competition experiments to analyze RNA populations.
- Infection of Bacillus subtilis with bacteriophage phi29 under various conditions (e.g., chloramphenicol, rifamycin).
Main Results:
- Early (e) phi29 RNA is synthesized from the light (L) DNA strand before and during viral DNA replication.
- Host RNA polymerase is sufficient for e RNA synthesis; no repression was observed.
- Late (l) phi29 RNA, including heavy (H) strand transcripts (lH), appears with DNA replication.
- lH RNA production requires protein synthesis and is essential for major phi29 structural protein synthesis.
Conclusions:
- Bacteriophage phi29 employs distinct temporal regulation for RNA synthesis, with early and late transcripts originating from different DNA strands.
- Late heavy-strand RNA synthesis is a critical regulatory step, linking viral DNA replication to the production of structural proteins.