Activates transcription from class II MHC promoters. Activation requires the activity of the MHC class II transactivator/CIITA. May regulate other genes in the cell. RFX binds the X1 box of MHC-II promoters ( ). May also potentiate the activation of RAF1 (By similarity).
Isoform 2 is not involved in the positive regulation of MHC class II genes.
Subcellular locations: Cytoplasm, Nucleus
Ubiquitous.