Protein-primed replication of bacteriophage phi 29 DNA

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• The phi 29 DNA-protein p3 replication system serves as a model for protein-priming mechanisms.
• Phi 29 DNA polymerase is a highly processive enzyme capable of strand displacement.
• Understanding the roles of viral proteins and DNA polymerase domains is crucial for elucidating replication strategies.

Purpose of the Study:

• To correlate functional and structural domains of phi 29 DNA polymerase.
• To map DNA-binding and protein-binding regions within the terminal protein.
• To investigate the roles of viral proteins p6 and p5 in phi 29 DNA replication initiation and elongation.

Main Methods:

• Construction and analysis of point and deletion mutants in phi 29 DNA polymerase and terminal protein.
• Biochemical assays to assess DNA polymerase activity (initiation, elongation, exonuclease).
• DNA-binding studies and protein-DNA interaction analysis using viral proteins p6 and p5.

Main Results:

• Mutations in the carboxyl region of phi 29 DNA polymerase decreased initiation and elongation but retained exonuclease activity, indicating its role in active site function.
• Mapping identified one DNA-binding region and two DNA-polymerase-binding regions in the terminal protein.
• Viral protein p6 binds to specific signals at DNA ends, stimulating replication. Viral protein p5 binds single-stranded DNA and enhances replication in vitro.

Conclusions:

• The carboxyl region of phi 29 DNA polymerase is critical for catalytic activity in replication.
• Specific domains within the terminal protein mediate interactions with DNA and DNA polymerase.
• Viral proteins p6 and p5 play distinct but essential roles in regulating phi 29 DNA replication initiation and efficiency.