IDENTIFICATION AND CHARACTERIZATION OF A PROTEIN-KINASE GENE IN THE LYMANTRIA-DISPAR MULTINUCLEOCAPSID NUCLEAR POLYHEDROSIS-VIRUS

The Lymantria dispar multinucleocapsid nuclear polyhedrosis virus (LdM NPV) gene encoding vPK has been cloned and sequenced. LdMNPV vPK shows a 24% amino acid identity to the catalytic domains of the eucaryotic protein kinases nPKC from rabbits, HSPKCE from humans, APLPKCB from Ap lysia californica, and dPKC98F from Drosophila melanogaster, and homol ogy to several other protein kinases from yeasts, mice, and bovines. T he homology suggests that vPK is a serine/threonine protein kinase as defined by Hanks et al. (S. K. Hanks, A. M. Quinn, and T. Hunter, Scie nce 241:42-52, 1988). Temporal expression studies indicate that vPK is expressed throughout the infection cycle beginning at 4 h postinfecti on, first as a delayed-early gene and subsequently as a late gene. Seq uence analysis and primer extension reactions confirm the presence of distinct early and late transcription initiation regions. Expression o f vPK with a rabbit reticulocyte system generated a 31-kDa protein, wh ich is in close agreement with the predicted size of 32 kDa from the a mino acid sequence. Phosphorylation activity of in vitro-expressed vPK was demonstrated by using calf thymus histones.