Protein-primed initiation of phage phi 29 DNA replication

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Bacteriophage phi 29 DNA replication is a model system for understanding DNA synthesis.
• The role of gene 3 protein (terminal protein) in phi 29 DNA replication initiation requires elucidation.

Purpose of the Study:

• To isolate and characterize the replication activity associated with bacteriophage phi 29 gene 3 protein.
• To investigate the role of the terminal protein in initiating phi 29 DNA replication in vitro.

Main Methods:

• Development of an in vitro replication system for bacteriophage phi 29 DNA.
• Utilized two assay systems: DNA replication dependent on DNA-protein and complex formation between terminal protein and dAMP.
• Purification of replication and complex-forming activities, followed by pulse-chase experiments and analysis of temperature-sensitive mutants.

Main Results:

• Replication and dAMP complex-forming activities were purified together.
• The terminal protein-dAMP complex effectively primes DNA chain elongation.
• Purified fraction contains functional gene 3 product, demonstrating specificity for phi 29 DNA-protein template and initiation at both termini.

Conclusions:

• The gene 3 protein of bacteriophage phi 29, acting as a terminal protein, is essential for initiating DNA replication.
• The terminal protein-dAMP complex serves as a primer for DNA synthesis.
• Results support the protein-priming model for the initiation of linear DNA synthesis.