Induction of p56 mRNA. Vero, HeLa, HEp2, SK-N-SH, HFF, U2OS, and HEL cells were mock treated, infected with KOS1.1 or ΔSma at an MOI of 10, or treated with 1,000 U IFN-α 6 h prior to harvest. RNA was extracted at 6 and 12 hpi and analyzed by Northern blotting with probes specific for p56 and γ-actin mRNA.