PHOSPHORYLATION OF SENDAI VIRUS PHOSPHOPROTEIN BY CELLULAR PROTEIN-KINASE-C-ZETA

The phosphoproteins (P) of nonsegmented negative strand RNA viruses ar e viral RNA polymerase subunits involved in both transcription and rep lication during the virus life cycle. Phosphorylation of P proteins in several negative strand RNA viruses by specific cellular kinases was found to be required for P protein function. In the present study, usi ng bacterially expressed unphosphorylated P protein of Sendai virus, a mouse parainfluenza virus, we have shown that the major cellular kina se that phosphorylates P protein in vitro is biochemically and immunol ogically indistinguishable from protein kinase C (PRC) zeta isoform. P KC zeta was packaged into the Sendai virion and remained associated wi th purified viral ribonucleoprotein, where it phosphorylated both the P and the nucleocapsid protein in vitro. When PHC zeta-specific inhibi tory pseudosubstrate peptide was introduced into LLC-MK2 cells prior t o Sendai virus infection, production of progeny virus was dramatically attenuated, and kinetic analysis revealed that primary transcription was repressed. These data indicate that phosphorylation of the Sendai virus P protein by PKC zeta plays a critical role in the virus life cy cle.