THE NS5A NS5 PROTEINS OF VIRUSES FROM 3 GENERA OF THE FAMILY FLAVIVIRIDAE ARE PHOSPHORYLATED BY ASSOCIATED SERINE/THREONINE KINASES/

Phosphorylation of the expressed NS5A protein of hepatitis C virus (HC V), a member of the Hepacivirus genus of the family Flaviviridae, has been demonstrated in mammalian cells and in a cell-free assay by an as sociated kinase activity. In this report, phosphorylation is also show n for the NS5A and NS5 proteins, respectively, of bovine viral diarrhe a virus (BVDV) and yellow fever virus (YF), members of the other two e stablished genera in this family. Phosphorylation of BVDV NS5A and YF NS5 was observed in infected cells, transient expression experiments, and a cell-free assay similar to the one developed for HCV NS5A, Phosp hoamino acid analyses indicated that all three proteins were phosphory lated by serine/threonine kinases, Similarities in the properties of B VDV NSSA, YF NS5, and HCV NS5A phosphorylation in vitro further sugges ted that closely related kinases or the same kinase may phosphorylate these viral proteins. Conservation of this trait among three quite dis tantly related viruses representing three separate genera suggests tha t phosphorylation of the NS5A/NS5 proteins or their association with c ellular kinases may play an important role in the flavivirus life cycl e.