DELETION OF FOWLPOX VIRUS HOMOLOGS OF VACCINIA VIRUS GENES BETWEEN THE 3-BETA-HYDROXYSTEROID DEHYDROGENASE (A44L) AND DNA-LIGASE (A50R) GENES

A fragment of 4156 bp of fowlpox virus (FPV) genomic DNA contains homo logues of vaccinia virus 3 beta-hydroxysteroid dehydrogenase/Delta(5)- Delta(4) isomerase (3 beta-HSD; A44L) and DNA ligase (A50R) genes. The FPV locus has clearly been rearranged relative to that of vaccinia vi rus as homologues of genes A45R to A49R, including the thymidylate kin ase and a gene with homology to superoxide dismutase, are deleted. The deleted genes are replaced by two open reading frames: for a serine p roteinase inhibitor with homology to vaccinia virus gene K2L and for a protein with no significant homology to proteins in the databases. In addition, the FPV homologues of A44L and A50R are in the same polarit y in FPV whereas they are in opposite polarities in vaccinia virus. In creased 3 beta-HSD activity has been demonstrated in cells infected wi th either of two different strains of FPV or with canarypox virus.