Phosphorylation of nonstructural 5A protein of hepatitis C virus: HCV group-specific hyperphosphorylation.

We previously showed that two proteins with molecular weights of 56 and 58 kDa are produced from nonstructural protein 5A (NS5A) derived from hepatitis C virus (HCV)-1b genotype. The 56-kDa protein is phosphorylated at serine residues in NS5A, including those located in the C-terminal region of NS5A, while the 58-kDa protein, the hyperphosphorylated form of the 56-kDa protein, is phosphorylated at serine residues in the central region. This hyperphosphorylation is dependent on the presence of HCV NS4A protein. To clarify whether NS4A-dependent phosphorylation also occurs in other HCV genotypes, phosphorylation of NS5A was analyzed by two-dimensional gel electrophoresis. Here, we report that NS5A from the HCV-2a genotype was phosphorylated. However, hyperphosphorylation of NS5A occurs in the HCV-1b genotype but not in the -2a genotype. This result suggests that modification of NS5A phosphorylation reflects the virological features of HCV and that there are physiological differences in the roles of differently phosphorylated NS5A between HCV genotypes. Copyright 1999 Academic Press.