Phosphorylation of STAT1

Phosphotyrosine on STAT2 acts as docking site for STAT1 molecules. STAT1 binds to phosphorylated STAT2 and this is followed by STAT1 phosphorylation on tyrosine residue 701 (Y701). These STATs recruited to the phosporylated IFNAR1 form two distinct transcriptional activator complexes, namely, IFN-alpha-activated factor (AAF) and IFN-stimulated gene factor 3 (ISGF3). AAF is a homodimer of STAT1, whereas ISGF3 is a heterotrimeric complex of STAT1, STAT2 and IRF9 (also known as p48 or ISGF3gamma) (Honda et al. 2005).

磷酸化酪氨酸位于STAT2上，充当STAT1分子的结合位点。STAT1与磷酸化的STAT2结合，随后在酪氨酸残基701（Y701）处发生STAT1的磷酸化。这些被招募至磷酸化IFNAR1上的STATs形成两个不同的转录激活复合体，即IFN-α激活因子（AAF）和IFN刺激基因因子3（ISGF3）。其中，AAF是STAT1的同源二聚体，而ISGF3是由STAT1、STAT2和IRF9（亦称为p48或ISGF3gamma）组成的异源三聚体（Honda等，2005年）。