THE RFX COMPLEX IS CRUCIAL FOR THE CONSTITUTIVE AND CIITA-MEDIATED TRANSACTIVATION OF MHC CLASS-I AND BETA(2)-MICROGLOBULIN GENES

In type III bare lymphocyte syndrome (BLS) patients, defects in the RF X protein complex result in a lack of MHC class II and reduced MHC cla ss I cell surface expression. Using type III BLS cell lines, we demons trate that the RFX subunits RFX5 and RFXAP are crucial for constitutiv e and CIITA-induced MHC class I and beta(2)m transactivation. Similar to MHC class II, the promoters of MHC class I and beta(2)m contain lan S-X-Y region of which the X1 box is crucial for constitutive and CIIT A-induced MHC class I and beta(2)m transactivation. Thus, the RFX comp lex is part of a regulatory pathway linking the transactivation of MHC class I and II and their accessory genes.