RFXAP: Regulatory Factor X-Associated Protein
Key transcription factor in MHC class II gene regulation and bare lymphocyte syndrome
Gene Information Card
| Symbol | RFXAP |
|---|---|
| Full Name | Regulatory Factor X-Associated Protein |
| Gene Type | Protein coding |
| Chromosomal Location | 13q13.3 |
| NCBI Gene ID | 5994 ncbi.nlm.nih.gov/gene/5994 |
| Ensembl ID | ENSG00000133111 |
| UniProt ID | O00287 |
| OMIM ID | 601861 |
| HGNC ID | 9989 |
| Aliases | RFX-B, ANKRA1 |
Description
RFXAP encodes the regulatory factor X-associated protein, a subunit of the RFX transcription factor complex that binds to the X-box motif of MHC class II gene promoters. This protein is essential for the expression of MHC class II molecules, which are critical for antigen presentation and immune response. Mutations in RFXAP cause bare lymphocyte syndrome type II, complementation group D, a severe immunodeficiency characterized by lack of MHC class II expression.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Bare lymphocyte syndrome type II (MHC class II deficiency) | Loss-of-function mutations in RFXAP prevent formation of functional RFX complex, abolishing MHC class II transcription | OMIM #209920; ClinVar; multiple case reports |
| Immunodeficiency with absent MHC class II expression | Same mechanism as above; autosomal recessive inheritance | OMIM; NCBI GeneReviews |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Lymph node | 12.3 | Medium |
| Spleen | 10.8 | Medium |
| Bone marrow | 8.5 | Low |
| Lung | 6.2 | Low |
| Testis | 5.1 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| B-lymphoblastoid cell line | 15.2 | High expression; model for MHC class II regulation |
| HeLa | 7.8 | Moderate expression |
| HEK293 | 6.4 | Low expression |
| Jurkat T cells | 4.1 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.266C>T (p.Pro89Leu) | Missense | Rare | Loss of function; disrupts RFX complex assembly |
| c.1A>G (p.Met1Val) | Start loss | Rare | Loss of function; no protein produced |
| c.325_326del (p.Leu109Valfs*2) | Frameshift | Rare | Loss of function; premature truncation |
Mutation functional classification
Loss of Function (LOF)
All reported pathogenic mutations in RFXAP are loss-of-function, leading to absent or non-functional protein, resulting in MHC class II deficiency.
Gain of Function (GOF)
No gain-of-function mutations have been reported for RFXAP.
Dominant Negative (DN)
No dominant-negative mutations have been described; inheritance is autosomal recessive.
View complete mutation data：
Gene Ontology (GO)
Pathways
• MHC class II antigen presentation (Reactome: R-HSA-2132295)
• Regulation of MHC class II gene expression (KEGG: hsa04612)
Protein Summary
RFXAP is a 272-amino acid protein that forms a heterotrimeric complex with RFX5 and RFXANK to create the RFX transcription factor. This complex binds the X-box promoter element of MHC class II genes (HLA-DP, -DQ, -DR) and recruits additional coactivators like CIITA. Without functional RFXAP, MHC class II expression is absent, leading to severe combined immunodeficiency.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| RFXAP Knockout HEK293 Cell Line | EDJ-KQ5654 | Human | 5994 | Details Get a Quote |
| RFXAP Knockout HCT 116 Cell Line | EDJ-KQ28998 | Human | 5994 | Details Get a Quote |
| RFXAP Knockout HeLa Cell Line | EDJ-KQ28999 | Human | 5994 | Details Get a Quote |
| RFXAP Knockout A-549 Cell Line | EDJ-KQ27734 | Human | 5994 | Details Get a Quote |
