Biochemical characterization and localization of JC virus large T antigen phosphorylation domains.
Large T antigen (T Ag), the major regulatory protein produced by the primate polyomaviruses, is a multifunctional phosphoprotein expressed early in the viral life cycle. T Ag performs many functions essential to viral DNA replication, and studies with SV40 T Ag indicate that the regulation of these functions is modulated, in part, by the phosphorylation status of this oncoprotein. In this study, we demonstrate that JC virus (JCV) T Ag obtained from lytically infected and transformed cells is phosphorylated at serine and threonine residues. Analysis of JCV T Ag via two-dimensional tryptic peptide mapping generates 14 phosphopeptides. Additional mapping studies of intact, hybrid, mutant, and truncated forms of JCV T Ag have aided the localization of phosphorylation sites to the N- or C-terminal region of the protein; both serine and threonine residues are modified at each terminus. The data indicate that, unlike the corresponding regulatory phosphorylation site Ser677 in SV40, Thr664 is not phosphorylated in JCV T Ag. The phosphorylation sites utilized for JCV T Ag, and the regulatory role of these sites, are predicted to contribute to the unique biology of this human virus.
Swenson
J J
JJ
Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park 16802, USA.
Frisque
R J
RJ
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed; D006801:Humans; D007577:JC Virus / Q000276:immunology*; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000032:analysis; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D017354:Point Mutation; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017384:Sequence Deletion
D000952:Antigens, Polyomavirus Transforming; D010748:Phosphopeptides; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D010769:Phosphothreonine; D010768:Phosphoserine