Interferon Regulatory Factor 9 (IRF9)

ISGF3 is an interferon-dependent, positive-acting transcription factor that is cytoplasmically activated, possibly through direct interaction with the interferon receptor.

The attachment of interferon-alpha (IFNA) to a specific cell surface receptor activates the transcription of a limited set of genes termed the IFN-stimulated genes. Supporting the notion that the proteins in ISGF3 are links between an occupied receptor and a limited set of genes were the observations that the proteins preexist in untreated cells, are promptly activated in an IFN-alpha-dependent fashion in the cell cytoplasm, and are subsequently translocated to the nucleus. Four proteins of 48 (ISGF3G), 84, 91, and 113 kD (STAT2) make up the ISGF3 complex.