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Myristylated polyomavirus VP2: role in the life cycle of the virus
N Krauzewicz1, C H Streuli, N Stuart-Smith
1Department of Virology, Royal Postgraduate Medical School, London, United Kingdom.
Abstract:
The double-stranded genome of the small DNA tumor virus, polyomavirus, is enclosed in a capsid composed of a major protein, VP1, which associates as pentameric capsomeres into an icosahedral structure, and two minor proteins, VP2 and VP3, whose functions and positions within the structure are unknown. The N-terminal glycine of the VP2 coat protein has been shown to be cotranslationally acylated with myristic acid. To study the function of this modification and the role of VP2 in the life cycle of polyomavirus, the N-terminal glycine, critical to the myristylation consensus sequence, has been altered to a glutamic acid or a valine residue by site-directed oligonucleotide mutagenesis. The glycine----glutamic acid mutant DNA has been further studied. When transfected into cells permissive for the polyomavirus full lytic life cycle, this mutant DNA replicated at levels comparable to those of wild-type viral DNA, and small amounts of nonrevertant (mutant) virus could be harvested from the cultures. The virus particles viewed by electron microscopy appeared slightly distorted, but the ratio of full to empty particles was similar to that produced in a wild-type viral infection. Mutant virus was capable of reinfecting permissive cells but with a considerably reduced efficiency.
Insights
Investigating polyomavirus VP2 protein myristylation revealed that altering the N-terminal glycine to glutamic acid impacts viral infectivity. This modification resulted in reduced efficiency of reinfection, highlighting VP2
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Polyomavirus has a double-stranded DNA genome within a capsid.
- The capsid comprises major protein VP1 and minor proteins VP2 and VP3.
- VP2's N-terminal glycine is cotranslationally myristylated, but its function is unknown.
Purpose of the Study:
- To investigate the function of VP2 myristylation in polyomavirus.
- To elucidate the role of VP2 in the viral life cycle.
Main Methods:
- Site-directed mutagenesis altered VP2's N-terminal glycine to glutamic acid or valine.
- Transfection of mutant DNA into permissive cells.
- Analysis of viral DNA replication, particle formation, and infectivity.
Main Results:
- The glycine-to-glutamic acid mutant replicated comparably to wild-type polyomavirus.
- Mutant virus particles showed slight distortions but similar full-to-empty ratios.
- Mutant virus exhibited significantly reduced efficiency in reinfecting permissive cells.
Conclusions:
- VP2 myristylation is crucial for efficient polyomavirus infection.
- Alterations in VP2 affect viral infectivity, though not viral replication or assembly.
- Further research is needed to understand VP2's precise role and structural contribution.