Characterization of vaccinia virus gene B12R

We report the characterization of vaccinia virus gene B12R which is predicted to encode a 33K protein with 36 % amino acid identity to the serine/threonine protein kinase encoded by vaccinia virus gene B 1R. S 1 nuclease protection experiments showed that gene B12R is transcribed early during infection from an initiation site 11 bp upstream of the open reading frame (ORF). The gene encodes a 33K polypeptide that is not required for virus replication in tissue culture nor for virus virulence in a murine intranasal model. Expression of the B12R gene in Eseherichia coil produced an abundant 33K polypeptide which lacked protein kinase activity under conditions in which the protein kinases encoded by vaccinia virus gene B1R and African swine fever virus gene j9L are active. Vaccinia virus, the prototype orthopoxvirus, is a large cytoplasmic virus. The dsDNA genome is predicted to encode more than 200 proteins many of which have amino acid sequence homology with cellular protein(s) (Goebel et al., 1990; Smith et al., 1991). Two genes, B1R and B12R, were predicted to encode related proteins (36 % amino acid identity) with omology to protein kinases (Howard & Smith, 1989; Traktman et al., 1989). Recently, the B1R gene product was shown to be a serine/threonine protein kinase that is required for virus DNA replication, it is packaged into virions and phosphorylates ribosomal proteins in vitro (Banham &amp