Functions of a protein kinase activity associated with purified capsids of the granulosis virus infecting Plodia interpunctella

Abstract

Activation of a protein kinase associated with purified capsids of the granulosis virus of Plodia interpunctella resulted in release of the DNA from the nucleocapsid as determined by electron microscopy. Heat treatment of the virions (65 degrees for 10 min) inactivated the kinase and prevented this uncoating event. The basic viral core protein, VP12, is the predominant phosphate acceptor for the protein kinase and was the only DNA-binding protein present in nucleocapsids. VP12 binding to 32P-nick-translated granulosis virus DNA was determined by the hybridization of the nick-translated DNA to nucleocapsid proteins transferred electrophoretically to nitrocellolose after separation by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Profiles obtained when nick-translated DNA was added to sucrose gradients in the absence and presence of VP12 substantiated the DNA-binding capability of VP12. Comparison of the DNA-binding capability of phosphorylated and nonphosphorylated VP12 using sucrose gradient sedimentation provided evidence that phosphorylation of the basic protein reduced its capability to bind DNA. We propose the endogenous protein kinase activity of the granulosis virus may function in two ways: release of the DNA from the nucleocapsid (uncoating), and decondensation of the DNA due to phosphorylation of the basic core protein, VP12.

Viral Aspects of Protein Phosphorylation

“…This proposal is based on the findings of experiments in which an endogenous protein kinase of VSV virions was activated by making it accessible to ATP in vitro, resulting in phosphorylation of the matrix M protein (which is not a DNA-binding protein) and disruption of the virion envelope (Witt et al, 1981). Similar experiments in vitro have led to proposals for a role for phosphorylation in the uncoating of an insect granulosis virus (Wilson & Consigli, 1985) and of poliovirus (Lackmann et al, 1987), both of which are non-enveloped viruses. What is lacking, however, is evidence for the action of these protein kinases or for a change in the phosphorylation state of the relevant virion proteins during uncoating in vivo.…”

The pk-1 Gene of Autographa Californica Multinucleocapsid Nuclear Polyhedrosis Virus Encodes a Protein Kinase

“…In this regard, PK-1 differs from the protein kinase associated with the granulosis virus infecting Plodia interpunctella, which requires MnC12 (Wilson & Consigli, 1985 a). The function of that kinase appears to be phosphorylation of the basic core protein VP12, resuting in release of DNA from the nucleocapsids, a key event early in infection (Wilson & Consigli, 1985b).…”

The p6.5 gene region of a nuclear polyhedrosis virus of Orgyia pseudotsugata: DNA sequence and transcriptional analysis of four late genes

“…Evidence for a protein kinase associated with virions has been reported for the granulosis virus of Plodia interpunctella (Wilson & Consigli, 1985). An antiserum produced against a synthetic peptide composed of part of the p6.9 sequence reacted with an acid-soluble, chromatinassociated protein of 6.9K (Wilson, 1988).…”