Protein kinase CK2 phosphorylation of EB2 regulates its function in the production of Epstein-Barr virus infectious viral particles |
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Authors: | Medina-Palazon Cahora Gruffat Henri Mure Fabrice Filhol Odile Vingtdeux-Didier Valérie Drobecq Hervé Cochet Claude Sergeant Nicolas Sergeant Alain Manet Evelyne |
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Affiliation: | INSERM U758, ENS-Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France. |
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Abstract: | The Epstein-Barr Virus (EBV) early protein EB2 (also called BMLF1, Mta, or SM) promotes the nuclear export of a subset of early and late viral mRNAs and is essential for the production of infectious virions. We show here that in vitro, protein kinase CK2alpha and -beta subunits bind both individually and, more efficiently, as a complex to the EB2 N terminus and that the CK2beta regulatory subunit also interacts with the EB2 C terminus. Immunoprecipitated EB2 has CK2 activity that phosphorylates several sites within the 80 N-terminal amino acids of EB2, including Ser-55, -56, and -57, which are localized next to the nuclear export signal. EB2S3E, the phosphorylation-mimicking mutant of EB2 at these three serines, but not the phosphorylation ablation mutant EB2S3A, efficiently rescued the production of infectious EBV particles by HEK293(BMLF1-KO) cells harboring an EB2-defective EBV genome. The defect of EB2S3A in transcomplementing 293(BMLF1-KO) cells was not due to impaired nucleocytoplasmic shuttling of the mutated protein but was associated with a decrease in the cytoplasmic accumulation of several late viral mRNAs. Thus, EB2-mediated production of infectious EBV virions is regulated by CK2 phosphorylation at one or more of the serine residues Ser-55, -56, and -57. |
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