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Synthesis of bacteriophage phiC DNA in dna mutants of Esherichia coli
Abstract:
Host dna functions involved in the replication of microvirid phage phiC DNA were investigated in vivo. Although growth of this phage was markedly inhibited even at 35-37 degrees C even in dna+ host, conversion of the infecting single-stranded DNA into the double-stranded parental replicative form (stage I synthesis) occurred normally at 43 degrees C in dna+, dnaA, dnaB, dnaC(D), and dnaE cells. In dnaG mutant, the stage I synthesis was severely inhibited at 43 degrees C but not at 30 degrees C. The stage I replication of phiC DNA was clearly thermosensitive in dnaZ cells incubated in nutrient broth. In Tris-casamino acids-glucose medium, however, the dnaZ mutant sufficiently supported synthesis of the parental replicative form. At 43 degrees C, synthesis of the progeny replicative form DNA (stage II replication) was significantly inhibited even in dna+ cells and was nearly completely blocked in dnaB or dnaC(D) mutant. At 37 degrees C, the stage II replication proceeded normally in dna+ bacteria.
Insights
Host DNA functions are crucial for microvirid phage phiC DNA replication. Specific host DNA mutants, like dnaG and dnaZ, show temperature-sensitive defects in early replication stages.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Microvirid phage phiC DNA replication relies on host DNA machinery.
- Understanding these host-phage interactions is key to viral replication mechanisms.
Purpose of the Study:
- To investigate the role of host DNA replication genes in the in vivo replication of microvirid phage phiC DNA.
- To identify specific host factors essential for different stages of phage DNA synthesis.
Main Methods:
- In vivo studies using various host DNA mutants (dnaA, dnaB, dnaC(D), dnaE, dnaG, dnaZ) at different temperatures (30°C, 37°C, 43°C).
- Monitoring of phage DNA synthesis, specifically stage I (parental replicative form) and stage II (progeny replicative form) replication.
Main Results:
- Stage I synthesis was largely unaffected in most mutants at 43°C, except for dnaG mutants at 43°C and dnaZ mutants in specific media.
- Stage II synthesis was significantly inhibited at 43°C in wild-type and even more so in dnaB or dnaC(D) mutants.
- Stage II replication proceeded normally at 37°C in wild-type bacteria.
Conclusions:
- Host dnaG and dnaZ proteins play critical roles in early phage DNA replication, exhibiting temperature sensitivity.
- Host dnaB and dnaC(D) proteins are essential for efficient progeny phage DNA synthesis (stage II).
- Phage phiC DNA replication is dependent on specific host DNA replication factors, with distinct requirements for different replication stages.