A T to A point mutation in 5' splice site of the STAT2 intron 4–5 resulted in diminished expression of STAT2 protein in P117. (A) Splenocytes of wild-type or P117 mice were stimulated with IFNγ or IFNα for 0, 3 and 6 h followed by Western blotting using antibodies to pSTAT1, STAT1, pSTAT2, STAT2, pSTAT3, STAT3 and β-actin. (B) Genomic sequencing results of wild-type (left panels) or P117 (middle panels). cDNA sequencing of p117 (right panels) indicated the addition of 5 nucleotides between exon 4 and exon 5. Schematic diagram of the mutation in the mouse STAT2 protein was shown (lower panel). PI: protein interaction, DBD: DNA binding domain, SH2: src homology 2, TAD: transactivation domain (C) Splenocytes of wild-type (empty bars), STAT2+/m (gray bars) and STAT2m/m (P117) (solid bars) mice were stimulated with IFNα (250 U/ml) for 0, 3 and 6 h, followed by RT-QPCR for OAS gene expression. Inset: response in STAT2m/m (P117) cells in a smaller scale. Western blotting was done using antibody to STAT2. Arrow head indicated full length STAT2. Relative mRNA was shown by normalizing the values of OAS to that of β-actin.