Analysis of the fowlpoxvirus gene encoding the 4b core polypeptide and demonstration that it possesses efficient promoter sequences.

The gene encoding the fowlpox virus 4b core polypeptide has been identified by analogy with the vaccinia 4b gene. It has been cloned, and its nucleotide sequence determined. The gene, which is 1971 nucleotides long, can encode a protein of 75,200 Da (75.2K polypeptide), slightly longer than its vaccinia counterpart with which it shares 52% identity. Sequences upstream of the fowlpox virus 4b gene correspond to the consensus sequence determined for vaccinia late promoters, suggesting that late promoter signals may be shared by the different genera of poxviruses. Upstream sequences have been cloned into a beta-galactosidase translational fusion vector and shown to promote the efficient expression of beta-galactosidase in a transient assay system. This expression was abolished in the presence of araC, an inhibitor of DNA replication which blocks late gene expression in poxviruses. The fowlpoxvirus 4b promoter should be a useful component of genetically engineered fowlpox virus vaccines.