Related Experiment Videos
DNA requirements in vivo for phage T4 packaging
1Department of Biochemistry, University of Maryland Medical School, Baltimore 21201-1503, USA.
Virology
|March 17, 1998
Summary
Phage T4 terminase packaging involves DNA sequence recognition. Increased gene copy number and specific DNA sequences (pac sites) enhance packaging efficiency, suggesting a synapsis model for T4 DNA packaging regulation.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage T4 terminase, composed of gene 16 and 17 products, packages DNA headfully from concatemers.
- The precise mechanism of DNA recognition by T4 terminase is not fully understood.
Purpose of the Study:
- To investigate the role of gene copy number and specific DNA sequences in phage T4 DNA packaging.
- To elucidate the mechanism of DNA recognition and packaging by phage T4 terminase.
Main Methods:
- Introducing phage T4 terminase gene sequences into prophage lambda imm434 and plasmids.
- Measuring packaging efficiency via transduction frequency and DNA content of T4-transducing particles.
- Analyzing the effect of mutations in the gene 16 3' region on packaging.
Main Results:
- Multiple copy prophage and high copy plasmids showed significantly increased transduction frequencies (100-1000 fold).
- T4 gene 16 inserts enhanced both prophage and plasmid packaging, with plasmid DNA exceeding 10% of total packaged DNA.
- Mutations in the gene 16 3' region, a potential T4 pac site, reduced elevated plasmid transduction frequencies.
- A specific gene 16-containing pac fragment was detected in mature, packaged T4 DNA.
Conclusions:
- Both homologous sequence copy number and specific DNA pac sequences are crucial for phage T4 packaging.
- Findings support a synapsis model for the regulation of terminase cutting and packaging in phage T4.