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Modulation of in vivo and in vitro transcription of bacteriophage phi 29 early genes
Abstract:
The majority of early transcripts of the phi 29 bacteriophage are produced throughout the lytic cycle but the levels of a class of transcripts from the right end of the phi 29 genome are significantly reduced late in the infection. We have isolated a phage early protein which selectively interferes with the initiation in vitro of transcription from promoters at the right end of the phi 29 genome. The amino acid sequence of the purified inhibitory protein correlates to the sequence predicted from the phi 29 gene 6 reading frame. In addition the inhibitory protein was not detectable in cells infected with phage mutated in gene 6 and the decrease in transcription did not occur in vivo when nonpermissive cells were infected with phi 29(sus6). The results indicate that the gene 6 protein modulates transcription from the right side of the phi 29 genome.
Insights
Phi 29 bacteriophage gene 6 protein regulates transcription. This protein selectively inhibits transcription initiation from the right genome end late in infection, impacting viral gene expression.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Phi 29 bacteriophage lytic cycle involves complex gene regulation.
- Specific transcripts from the right genome end are downregulated late in infection.
Purpose of the Study:
- To identify the phage protein responsible for reduced transcription of right-end genes.
- To elucidate the mechanism of transcriptional regulation by this protein.
Main Methods:
- Isolation and purification of a phage early protein.
- In vitro transcription assays to test for inhibitory activity.
- Amino acid sequencing and correlation with gene 6 reading frame.
- Analysis of transcription in cells infected with gene 6 mutated phage.
Main Results:
- An early phage protein was isolated that inhibits in vitro transcription initiation from right-end promoters.
- The protein's amino acid sequence matches the phi 29 gene 6 reading frame.
- The inhibitory protein is absent in gene 6 mutants, and transcription downregulation is abolished in vivo with phi 29(sus6).
Conclusions:
- The phi 29 gene 6 protein is a transcriptional regulator.
- Gene 6 protein selectively modulates transcription from the right side of the phi 29 genome.