FIG. 7.
In vivo and in vitro transcription mediated by A21− and A21+ virions. (A) Northern blot analysis. BS-C-1 cell monolayers were infected with 5 PFU per cell of wild type VACV WR, A21+ virions, or the corresponding OD260 of A21− virions. Total RNA was harvested at 3 h after infection and analyzed by gel electrophoresis and Northern blotting with [α-32P]dCTP-labeled double-stranded DNA probes to C11R, E9L, and β-actin transcripts. (B) In vitro transcription. Purified virions were incubated in reaction buffer containing NP-40, DTT, Mg++, ribonucleoside triphosphates, and [α-32P]UTP. Incorporation of [α-32P]UMP into trichloroacetic acid-insoluble material was determined by scintillation counting and is expressed as counts per minute (cpm).