Protein synthesis in cells infected by Autographa californica nuclear polyhedrosis virus (Ac-NPV): The effect of cytosine arabinoside

Abstract

Twenty-two virion polypeptides (VP) were detected reproducibly when the occluded form (OV) of [ 35S]methionine-labeled Ac-NPV, purified from polyhedral inclusion bodies (PIB), was analyzed by polyacrylamide gel electrophoresis and autoradiography. Ten of the VPs and the polyhedral protein (PP) were phosphorylated and 6 VPs were glycoproteins. Purified, nonoccluded virus (NOV) revealed 25 polypeptides. During a single cycle of virus replication, the synthesis of 33 infected cell polypeptides (1CP) was detected in different relative proportions at different times. They were arbitrarily designated as early (0–12hr), middle (12–18 hr), and late 18–24 hr) polypeptides. Most of the middle and late proteins seemed to be viral structural proteins. Rapid post -translat ional cleavage of IPCs was not observed; however, pulse-chase experiments revealed post-translational modifications of at least four polypeptides. Inhibition of DNA synthesis at the time of infection did not prevent the synthesis of ICPs, VPs, or the formation of PIBs. Progeny PIB from both control and cysosine arabinoside (Ara C)-treated cells that were infected with radiochemically pure [ 3H]thymidine-labeled NOV contained parental virus DNA. Electron micrographs of thin sections showed that, whereas PIBs from control cultures contained complete virions, those from Ara (C-treated cells contained both full and empty virus.