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Replication and packaging of choleraphage phi 149 DNA.
1Biophysics Division, Indian Institute of Chemical Biology, Calcutta.
Journal of Virology
|December 1, 1987
Summary
Choleraphage phi 149 DNA replication produces large concatemers in the cytoplasm. These concatemers are processed into mature phage DNA via a headful packaging mechanism initiated at a specific site.
Area of Science:
- Molecular Biology
- Virology
- Bacteriology
Background:
- Choleraphage phi 149 is a virus that infects bacteria.
- Bacteriophage DNA replication often involves complex intermediates.
- Understanding phage DNA packaging is crucial for viral assembly.
Purpose of the Study:
- To elucidate the mechanism of intercellular DNA replication for choleraphage phi 149.
- To investigate the structure and role of DNA concatemers in phage phi 149 replication.
- To determine the process of mature phage DNA packaging.
Main Methods:
- Analysis of DNA synthesis during phage phi 149 infection.
- Characterization of monomeric and concatemeric DNA intermediates.
- Investigation of DNA packaging into phage heads.
Main Results:
- Replication of choleraphage phi 149 DNA occurs in the cytoplasm, forming concatemeric structures up to six genome lengths.
- These concatemers act as substrates for mature phage DNA synthesis.
- DNA packaging into phage heads utilizes a headful mechanism initiated at a unique pac site on the concatemers.
- A model proposes sequential packaging of five headfuls counterclockwise from the pac site.
- High-phosphate conditions inhibit concatemer formation without affecting monomer synthesis.
Conclusions:
- The intercellular replication of choleraphage phi 149 involves cytoplasmic synthesis of large DNA concatemers.
- Concatemeric DNA is essential for producing mature phage DNA and is packaged via a specific headful mechanism.
- Environmental factors like phosphate levels can modulate concatemer formation during replication.