HEPATITIS-C VIRUS NS5A PROTEIN IS PHOSPHORYLATED IN-VITRO BY A STABLYBOUND PROTEIN-KINASE FROM HELA-CELLS AND BY CAMP-DEPENDENT PROTEIN-KINASE A-ALPHA CATALYTIC SUBUNIT

Hepatitis C virus (HCV) has a positive-strand RNA genome that codes fo r a polyprotein precursor, which is processed co-and post-translationa lly by cellular and viral proteinases into three structural and at lea st six non-structural (NS) proteins. The NS5A protein, expressed in ma mmalian cells, exists in two phosphorylated forms of 56-kDa and 58-kDa . In this study, we provide evidence for a stable association between NS5A and a protein kinase from HeLa cells and hepatocellular carcinoma (HepG2) cells by co-immunoprecipitation and by affinity to immobilize d glutathione-S-transferase (GST)-NS5A fusion protein produced in E. c oli. This protein kinase could phosphorylate in vitro the native NS5A on serine residues, (GST)-NS5A, histone H1, and casein as substrates. In addition, the GST-NS5A was also phosphorylated in vitro by the cAMP -dependent protein kinase A-alpha catalytic subunit. (C) 1997 Elsevier Science B.V.