AFRICAN SWINE FEVER VIRUS ENCODES A SERINE PROTEIN-KINASE WHICH IS PACKAGED INTO VIRIONS

Nucleotide sequencing of the SalI j region of the virulent Malawi (LIL 20/1) strain of African swine fever virus (ASFV) identified an open re ading frame (ORF), designated j9L, with extensive similarity to the fa mily of protein kinases. This ORF encodes a 35.1-kDa protein of 299 am ino acids which shares 24.6% amino acid identity with the human pim-1 proto-oncogene and 21.0% identity with the vaccinia virus BIR-encoded protein kinase. The ASFV ORF contains the motifs characteristic of ser ine-threonine protein kinases, with the exception of the presumed ATP- binding site, which is poorly conserved. The ORF was expressed to high levels in Escherichia coli, and the recombinant enzyme phosphorylated a calf thymus histone protein on serine residues in vitro. An antibod y raised to an amino-terminal peptide of the ASFV protein kinase was r eactive with the recombinant protein in Western immunoblot analyses an d was used to demonstrate the presence of the protein kinase in ASF vi rions.