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Bacteriophage lambda N protein alone can induce transcription antitermination in vitro
W A Rees1, S E Weitzel, T D Yager
1Institute of Molecular Biology, University of Oregon, Eugene 97403, USA.
Summary
Bacteriophage lambda N protein alone can induce antitermination, but requires specific RNA structures and Nus factors for efficient and processive activity. The study elucidates the complex interactions governing this essential viral gene regulation mechanism.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage lambda N protein mediates antitermination, a crucial process for viral gene expression.
- This process typically requires Escherichia coli Nus factors and a specific boxB RNA hairpin within the nut site.
Purpose of the Study:
- To investigate the role of N protein alone and in combination with other factors in antitermination.
- To elucidate the molecular mechanisms underlying N-mediated antitermination, including the contribution of the nut site and NusA.
Main Methods:
- In vivo and in vitro antitermination assays.
- Competition assays using excess boxB RNA.
- Analysis of N protein interaction with transcription complexes using an equilibrium binding model.
Main Results:
- N protein alone can induce nonprocessive antitermination at high concentrations, independent of the nut site.
- Antitermination efficiency is significantly enhanced by the presence of nut+ RNA and further increased by NusA.
- NusA-dependent enhancement is lost with delta nut transcripts, suggesting a specific N-NusA-boxB RNA complex.
Conclusions:
- The N protein-boxB RNA interaction is critical for efficient antitermination.
- NusA stabilizes the transcription complex, increasing antitermination processivity.
- The study provides insights into the quantitative aspects of N protein binding and dissociation, explaining processivity differences.