An entomopoxvirus homologue of the vaccinia virus D13L-encoded 'rifampicin resistance' protein.

The Heliothis armigera entomopoxvirus (HaEPV) genome encodes a predicted 68 kDa polypeptide related to the 'rifampicin resistance' protein of vaccinia virus (with 30 % identity), and an homologous swinepox virus protein (27% identity). We were unable to isolate an HaEPV genotypic variant encoding a predicted C-terminal truncated form of the protein, suggesting that the C terminus of the molecule may be essential to protein function, and, in turn, that this function may be essential to viral replication. HaEPV replication was substantially reduced in host cells exposed to rifampicin, but the observed cytotoxic properties of the drug made it impossible to determine the specific cause of that inhibition. We suggest that possession of a gene encoding a member of this polypeptide family might represent a defining molecular characteristic of the Poxviridae.