Regulatory Factor X-Associated Ankyrin-Containing Protein （RFXANK） contains ankyrin repeats involved in protein-protein interactions. RFXANK， along with regulatory factor X-associated protein and regulatory factor-5， figures a complex which binds to the X box motif of certain MHC class II gene promoters and activates their transcription. After bound to the promoter， this complex associates with the non-DNA-binding factor MHC class II transactivator， which controls the cell type specificity and inducibility of MHC class II gene expression. Mutations in RFXANK have been linked to bare lymphocyte syndrome type II， complementation group B.
