FIG. 2.

Transcription activity of Stat1 point mutants. (a) Transient transfections were carried out with the U3A (no Stat1) cell line by using the indicated Stat1 expression vectors. Transcriptional responses to IFN-γ were monitored by the 3×Ly6E GAS-LUC reporter plasmid after 4 h of IFN-γ stimulation. This experiment was performed three times, each time with triplicate samples. A representative experiment is shown with the standard errors for the three samples. (b) RT-PCR analysis was performed by using wild-type-complemented (Stat1α) or mutant-complemented [Stat1(KE544-545AA)] U3A-derived stable cell lines. Cells were treated with the specified interferon for 4 h or left untreated, followed by RNA harvesting and reverse transcription. PCR amplification of the resulting cDNAs with radioactive nucleotides was performed with a primer pair representing the mRNAs indicated on the left. The products were resolved by acrylamide electrophoresis and autoradiography.