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Temporal regulation of herpes simplex virus type 2 VP22 expression and phosphorylation
B J Geiss1, J E Tavis, L M Metzger
1Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Journal of Virology
|October 17, 2001
Summary
Herpes simplex virus type 2 (HSV-2) VP22 protein undergoes rapid, virus-dependent phosphorylation after synthesis. This stable protein is later dephosphorylated to form the virion tegument, independent of DNA replication or assembly.
Area of Science:
- Virology
- Molecular Biology
- Protein Biochemistry
Background:
- Herpes simplex virus type 2 (HSV-2) VP22 is a key tegument protein.
- Phosphorylation of HSV-1 VP22 suggests a role in cellular localization.
- The synthesis and phosphorylation regulation of HSV-2 VP22 remain largely uncharacterized.
Purpose of the Study:
- To elucidate the complete biosynthetic history of HSV-2 VP22.
- To investigate the timing, regulation, and isoforms of HSV-2 VP22 phosphorylation.
- To determine the role of HSV-2 kinase UL13 in VP22 phosphorylation.
Main Methods:
- Generation of a monoclonal antibody against HSV-2 VP22.
- Immunoprecipitation and Western blot analyses to detect VP22 isoforms.
- In vitro kinase assays using HSV-2 UL13.
Main Results:
- HSV-2 VP22 exists in three isoforms in infected cells; two are phosphorylated.
- Newly synthesized VP22 is rapidly phosphorylated in a virus-dependent manner.
- HSV-2 kinase UL13 phosphorylates VP22 independently of other viral proteins.
- Phosphorylated VP22 is stable and gradually dephosphorylated late in infection to yield the hypophosphorylated virion form.
- Dephosphorylation occurs independently of viral DNA replication or virion assembly.
Conclusions:
- HSV-2 VP22 is a stable protein with a highly regulated phosphorylation cycle.
- Phosphorylation and dephosphorylation of VP22 are critical, virus-dependent events.
- The HSV-2 UL13 kinase plays a direct role in VP22 phosphorylation.