N phosphorylation affects viral RNA transcription in the minigenome. BSR cells were infected with recombinant vaccinia virus vTF7-3 and then transfected with plasmid pRP, pT7T-L, pSDI-CAT together with pRN (RN), pRN-SA (SA), pRN-SG (SG), pRN-SD (SD), pRN-SN (SN), pRN-SE (SE), or pRN-SQ (SQ). Cells were harvested for measurement of CAT activity by the Quan-T-CAT assay. Error bars, standard deviations.