RT-PCR of STAT1 transcript. Three cell lines were subject to RT-PCR, including HUT78R, HUT78S, and HeLa cells. Primer 1 (5′AAGGTGGCAGGATGTCTCGTG-3′) spans the STAT1 translational initiation site and is complementary to nucleotides 186-207. Primer 2 (5′TGGTCTCGTGTTCTTCTGTTCTG-3′) covers the junction of exon 5 and 6 and is complementary to bases 728-749. The actin mRNA was amplified using primers that are commercially available.