Toxoplasma gondii Triggers Phosphorylation and Nuclear Translocation of Dendritic Cell STAT1 while Simultaneously Blocking IFNγ-Induced STAT1 Transcriptional Activity
Nuclear extracts were prepared from cells infected with the RH parasite strain (Tg, Toxoplasma gondii; 3∶1 parasites to cells) or treated with IFNγ (100 ng/ml) for 6 hours. The in vitro binding activity of nuclear STAT1 to solid phase IFNγ-activated sequence (GAS) oligonucleotides was assessed using an ELISA-based method. Binding activity is expressed as fold increase over cells cultured in medium alone (Med, value of 1). +cOligo, addition of soluble competitive oligonucleotides; +mOligo, addition of mutated non-competitive oligonucleotides. The experiment was repeated three times with similar results. *, p<0.05 comparing nuclear extracts alone with nuclear extracts plus cOligo.