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Functions of gene C and gene D products of bacteriophage phi X 174
Abstract:
Phage-related materials existing in cells infected with various mutants of bacteriophage phi chi 174 were investigated. A novel species of replicative-form (RF) DNA was found in cells infected with a phage mutant of gene B, C, D, F, or G. This species, called RFI, sedimented at a position between RFI and RFII in a neutral sucrose gradient. It was converted to RFI upon denaturation in alkali, denaturation in formamide and subsequent renaturation, or RNase treatment at low ionic strength. In cells infected with a phage mutant of gene C, RFI was derived from pulse-labeled RFII after a short chase. TLLS INFECTED WITH A MUTANT OF GENE B, D, or F. A possible function of the C gene product of phi chi 174 could be to prevent the conversion of RFII to RFI, thereby maintaining the availability of RFII to act as the template for single-stranded viral DNA synthesis. A protein complex containing no DNA, which sedimented with an S value of 108 in a sucrose gradient and contained virion proteins F, G, and H, and nonvirion protein D, was found in cells infected with the gene C mutant. A possible function of protein D was considered as a scaffolding protein for assembly of phage structural proteins.
Insights
Researchers discovered a new DNA form, RFI, in bacteriophage phi chi 174 mutants. This finding sheds light on viral DNA replication and protein assembly in infected cells.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage phi chi 174 is a well-studied model organism for DNA replication.
- Understanding viral DNA replication mechanisms is crucial for developing antiviral strategies.
Purpose of the Study:
- To investigate phage-related materials in cells infected with bacteriophage phi chi 174 mutants.
- To characterize a novel replicative-form (RF) DNA species and associated protein complexes.
Main Methods:
- Neutral sucrose gradient sedimentation analysis of DNA.
- Alkali and formamide denaturation/renaturation experiments.
- RNase treatment and pulse-chase labeling experiments.
- Sucrose gradient sedimentation of protein complexes.
Main Results:
- A novel RF DNA species, termed RFI, was identified in cells infected with mutants in genes B, C, D, F, or G.
- RFI exhibited distinct sedimentation properties and could be converted to RFI under specific conditions.
- In gene C mutants, RFI was derived from RFII after a short chase.
- A DNA-free protein complex (S value 108) containing virion proteins (F, G, H) and nonvirion protein D was found in gene C mutants.
Conclusions:
- The C gene product may regulate the conversion of RFII to RFI, ensuring RFII availability for viral DNA synthesis.
- Protein D might function as a scaffolding protein in the assembly of bacteriophage phi chi 174 structural proteins.