In vitro recognition of an orf virus early promoter in a vaccinia virus extract.

DNA fragments containing varying lengths of the 5' end of an orf virus early gene (ORF3) and its associated promoter were introduced into sodium deoxycholate-solubilized vaccinia virus extracts capable of initiating transcription in vitro from vaccinia virus early promoters. After separation of the radiolabelled products of the reactions on a 5% polyacrylamide/7 M urea gel, discrete transcripts were detected the sizes of which were consistent with initiation of transcription from the orf virus early promoter. This is the first demonstration in a functional assay of the conservation of early transcriptional promoters between an orthopoxvirus and a parapoxvirus.