An in vitro transcription system for studying vaccinia virus early genes.

Transcription of the vaccinia virus early genes occurs within the confines of the virion core structure. Therefore, isolated virions are a particularly rich source of proteins that function in early mRNA biosynthesis. Methods are described here for the extraction of purified vaccinia virions to yield protein mixtures with high transcriptional activity on viral early gene templates, responding specifically to both transcriptional initiation and termination signals in the DNA.