Activity of a fowlpox virus late gene promoter in vaccinia and fowlpox virus recombinants.

Characterization of a late promoter of fowlpox virus (FPV) and a study of its activity in FPV and vaccinia virus (VV) was carried out. The 5'-mRNA start site of the FPV late gene mapped to a TAAAT sequence near the translation start site (ATG). A cloned DNA fragment of FPV genome (PFL1) comprising of the 5'-end of the late gene was used to express the LacZ gene of E. coli in FPV and VV recombinants. A comparative analysis of beta-galactosidase (BG) expression from the LacZ gene under the control of the FPV promoter and a VV late promoter (PL11) was performed. Like FPV-PL11-LacZ and VV-PL11-LacZ constructs, FPV-PFL1-LacZ and VV-PFL1-LacZ virus recombinants expressed BG indicating that essential features of transcription were conserved in the two viruses. Furthermore, the LacZ transcripts originating from PFL1 in FPV and VV recombinants mapped to the expected TAAAT sequence. Time course analysis of BG expressed by VV and FPV recombinants suggested that although the transcription machinery in the two viruses was essentially conserved, subtle differences in the efficiency of transcription or translation may exist.