The RFX Complex Is Crucial for the Constitutive and CIITA-Mediated Transactivation of MHC Class I and β2-Microglobulin Genes

AbstractIn type III bare lymphocyte syndrome (BLS) patients, defects in the RFX protein complex result in a lack of MHC class II and reduced MHC class I cell surface expression. Using type III BLS cell lines, we demonstrate that the RFX subunits RFX5 and RFXAP are crucial for constitutive and CIITA-induced MHC class I and β2m transactivation. Similar to MHC class II, the promoters of MHC class I and β2m contain an S-X-Y region of which the X1 box is crucial for constitutive and CIITA-induced MHC class I and β2m transactivation. Thus, the RFX complex is part of a regulatory pathway linking the transactivation of MHC class I and II and their accessory genes