The avian polyomavirus budgerigar fledgling disease virus (BFDV) encodes an unusual set of four agnoproteins in its late upstream region. Of the two pairs of these proteins, which overlap each other in two different reading frames, the p-promoted agnoprotein-1a (agno-1a) is the dominant species and is able to support virus propagation in the absence of the other three polypeptides. Viral BFDV agno-1a, and also agno-1a expressed via an influenza virus vector, consists of a complex series of electrophoretically separable subspecies that can be reduced by phosphatase action down to a primary unphosphorylated protein with an apparent molecular mass of 31 kDa. Through peptide mass spectrometry and site-directed mutagenesis, the positions of four serine and three threonine residues have been determined as phosphate-accepting groups, which are partially modified by the combined action of three different cellular kinases. Since extensively phosphorylated agno-1a is required for its intracellular function, control over VP protein expression, and unphosphorylated agno-1a is observed as an additional component in the BFDV virion, both extreme subspecies appear to be drawn from that complex mixture, which also includes the intermediate stages of phosphorylation.


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  1. Bozeman, L. H., Davis, R. B., Gaudry, D., Lukert, P. D., Fletcher, O. J. & Dykstra, M. J. (1981). Characterization of a papovavirus isolated from fledgling budgerigar. Avian Disease 25, 972-980.[CrossRef] [Google Scholar]
  2. Fouts, D. E., True, H. L., Cengel, K. A. & Celander, D. W. (1997). Site-specific phosphorylation of the human immunodeficiency virus type-1 rev protein accelerates formation of an efficient RNA-binding conformation. Biochemistry 36, 13256-13262.[CrossRef] [Google Scholar]
  3. Green, P. L., Yip, M. T., Xie, Y. & Chen, I. S. Y. (1992). Phosphorylation regulates RNA binding by the human T-cell leukemia virus rex protein. Journal of Virology 66, 4325-4330. [Google Scholar]
  4. Haynes, J. I.II & Consigli, R. A. (1992). Phosphorylation of the budgerigar fledgling disease virus major capsid protein VP1. Journal of Virology 66, 4551-4555. [Google Scholar]
  5. Jackson, V. & Chalklay, R. (1981). Use of whole-cell fixation to visualize replicating and maturing simian virus 40: identification of new viral gene product. Proceedings of the National Academy of Sciences, USA 78, 6081-6085.[CrossRef] [Google Scholar]
  6. Johne, R. & Müller, H. (1998). Avian polyomavirus in wild birds: genome analysis of isolates from Falconiformes and Psittaciformes. Archives of Virology 143, 1501-1512.[CrossRef] [Google Scholar]
  7. Kozak, M. (1987). An analysis of 5′-noncoding sequences from 699 vertebrate messenger RNAs. Nucleic Acids Research 15, 8125-8148.[CrossRef] [Google Scholar]
  8. Laemmli, U. K. (1970). Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227, 680-685.[CrossRef] [Google Scholar]
  9. Lehn, H. & Müller, H. (1986). Cloning and characterization of budgerigar fledgling disease virus, an avian polyomavirus. Virology 151, 362-370.[CrossRef] [Google Scholar]
  10. Li, J. (1997).Molecular analysis of late gene expression in BFDV. PhD thesis, University of Giessen.
  11. Li, M. & Garcea, R. L. (1994). Identification of the threonine phosphorylation sites on the polyomavirus major capsid protein VP1: relationship to the activity of middle T antigen.Journal of Virology 68, 320-327. [Google Scholar]
  12. Liu, Q. & Hobom, G. (1999). Recombinant expression of late genes agno-2a and agno-2b of avian polyomavirus BFDV. Virus Genes 19, 183–187.[CrossRef] [Google Scholar]
  13. Lochnit, G., Nispel, S., Dennis, R. D. & Geyer, R. (1998). Structural analysis and immunohistochemical localization of two acidic glycosphingolipids from the porcine parasitic nematode, Ascaris suum.Glycobiology 8, 891-899.[CrossRef] [Google Scholar]
  14. Luo, D., Müller, H., Tang, X.-B. & Hobom, G. (1995). Early and late pre-mRNA processing of budgerigar fledgling disease virus 1: identification of viral RNA 5′ and 3′ ends and internal splice junctions. Journal of General Virology 76, 161-166.[CrossRef] [Google Scholar]
  15. Neumann, G. & Hobom, G. (1995). Mutational analysis of influenza virus promoter elements in vivo. Journal of General Virology 76, 1709-1717.[CrossRef] [Google Scholar]
  16. Pinna, L. A. (1990). Casein kinase 2: an ‘eminence grise’ in cellular regulation? Biochimica et Biophysica Acta 1054, 267-284.[CrossRef] [Google Scholar]
  17. Quadroni, M., L’Hostis, E. L., Corti, C., Myagkikh, I., Durussel, I., Cox, J., James, P. & Carafoli, E. (1998). Phosphorylation of calmodulin alters its potency as an activator of target enzymes. Biochemistry 37, 6523-6532.[CrossRef] [Google Scholar]
  18. Resnick, J. & Shenk, T. (1986). Simian virus 40 agnoprotein facilitates normal nuclear location of the major capsid polypeptide and cell-to-cell spread of virus. Journal of Virology 60, 1098-1106. [Google Scholar]
  19. Rinaldo, C. H., Traavik, T. & Hey, A. (1998). The agnogene of the human polyomavirus BK is expressed. Journal of Virology 72, 6233-6236. [Google Scholar]
  20. Roack, P. J. (1991). Multisite and hierarchical protein phosphorylation. Journal of Biological Chemistry 266, 14139-14142. [Google Scholar]
  21. Rott, O., Kroeger, M., Mueller, H. & Hobom, G. (1988). The genome of budgerigar fledgling disease virus, an avian polyomavirus. Virology 165, 74-86.[CrossRef] [Google Scholar]
  22. Stoll, R., Luo, D., Kouwenhoven, B., Hobom, G. & Mueller, H. (1993). Molecular and biological characteristics of avian polyomaviruses: isolates from different species of birds indicate that avian polyomaviruses form a distinct subgenus within the polyomavirus genus. Journal of General Virology 74, 229-237.[CrossRef] [Google Scholar]
  23. Stoll, R., Hobom, G. & Müller, H. (1994). Host restriction in the productive cycle of avian polyomavirus budgerigar fledgling disease virus type 3 depends on a single amino acid change in the common region of structural proteins VP2/VP3. Journal of General Virology 75, 2261-2269.[CrossRef] [Google Scholar]
  24. Zhou, Y., König, M., Hobom, G. & Neumeier, E. (1998). Membrane-anchored incorporation of a foreign protein in recombinant influenza virions. Virology 246, 83-94.[CrossRef] [Google Scholar]

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