This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sariyer, I. K.
Right arrow Articles by Safak, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sariyer, I. K.
Right arrow Articles by Safak, M.

 Previous Article  |  Next Article 

Journal of Virology, April 2006, p. 3893-3903, Vol. 80, No. 8
0022-538X/06/$08.00+0     doi:10.1128/JVI.80.8.3893-3903.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Phosphorylation Mutants of JC Virus Agnoprotein Are Unable To Sustain the Viral Infection Cycle

Ilker K. Sariyer, Ilhan Akan, Victoria Palermo, Jennifer Gordon, Kamel Khalili, and Mahmut Safak*

Department of Neuroscience, Center for Neurovirology, Laboratory of Molecular Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 442, Philadelphia, Pennsylvania 19122

Received 30 August 2005/ Accepted 19 January 2006

Many eukaryotic and viral regulatory proteins are known to undergo posttranslational modifications including phosphorylation, which plays a critical role in many aspects of cell function. Previous studies from our and other laboratories indicated that the JC virus (JCV) late regulatory protein, agnoprotein, plays an important role in the JCV life cycle. Agnoprotein contains several potential phosphorylation sites, including Ser7, Ser11, and Thr21, which are potential targets for the serine/threonine-specific protein kinase C (PKC). In this study, we investigated the functional significance of these phosphorylation sites for the activity of agnoprotein. In vitro and in vivo kinase assays demonstrated that agnoprotein is a target for phosphorylation by PKC. In addition, each of the PKC phosphorylation sites was mutated to Ala singly and in combination, and the effects of these mutations on the JCV life cycle were analyzed. Although the expression of each mutant agnoprotein was detectable during the infection cycle, virus containing each of these mutations failed to propagate. These results contrast with those obtained with an agnoprotein start codon point (Pt) mutant where agnoprotein expression was completely inhibited. The Pt mutant was viable but replicates less efficiently than the wild type (WT). Moreover, conservative substitutions at PKC phosphorylation sites (Ser7, Ser11, and Thr21 to Asp) resulted in a viable virus, which further demonstrate the importance of these sites on agnoprotein function. Further analysis of the mutants by viral release assay and electron microscopy studies revealed that viral particles were efficiently released from infected cells and morphologically indistinguishable from those of WT but were deficient in DNA content. This may account for the defective propagation of the mutants. These results imply that phosphorylated forms of agnoprotein may have essential functions in the viral life cycle and serve as potential targets for therapeutic interventions to limit JCV propagation and JCV-induced diseases.

* Corresponding author. Mailing address: Department of Neuroscience, Center for Neurovirology, Laboratory of Molecular Neurovirology, Temple University School of Medicine, 1900 North 12th St., 015-96, Rm. 442, Philadelphia, PA 19122. Phone: (215) 204-6340. Fax: (215) 204-0679. E-mail: msafak{at}temple.edu.

Journal of Virology, April 2006, p. 3893-3903, Vol. 80, No. 8
0022-538X/06/$08.00+0     doi:10.1128/JVI.80.8.3893-3903.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • White, M. K., Safak, M., Khalili, K. (2009). Regulation of Gene Expression in Primate Polyomaviruses. J. Virol. 83: 10846-10856 [Abstract] [Full Text]  
  • Merabova, N., Kaniowska, D., Kaminski, R., Deshmane, S. L., White, M. K., Amini, S., Darbinyan, A., Khalili, K. (2008). JC Virus Agnoprotein Inhibits In Vitro Differentiation of Oligodendrocytes and Promotes Apoptosis. J. Virol. 82: 1558-1569 [Abstract] [Full Text]  


Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»