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Gene Review

RFX1  -  regulatory factor X, 1 (influences HLA...

Homo sapiens

Synonyms: EF-C, EFC, Enhancer factor C, MHC class II regulatory factor RFX1, RFX, ...
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Disease relevance of RFX1

  • RFX1, a transactivator of hepatitis B virus enhancer I, belongs to a novel family of homodimeric and heterodimeric DNA-binding proteins [1].
  • Identification of an epigenetically silenced gene, RFX1, in human glioma cells using restriction landmark genomic scanning [2].
  • Hybrid protein effectors between RFX1 and RFX5 and the activation domain of VP16 from the herpes simplex virus were co-expressed with plasmid targets, which contained the isolated X box, X box and selected flanking CUS, or the entire DRA promoter [3].
  • In 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 [4].
  • The Epstein-Barr virus promoter initiating B-cell transformation is activated by RFX proteins and the B-cell-specific activator protein BSAP/Pax5 [5].

High impact information on RFX1

  • The study of RFX and CIITA has made major contributions to our comprehension of the molecular mechanisms controlling MHCII genes and has made this system into a textbook model for the regulation of gene expression [6].
  • The finding that RFX5 is a subunit of the nuclear RFX-complex has confirmed that a deficiency in the binding of this complex is indeed the molecular basis for MHC-II deficiency in the majority of patients [7].
  • Its interaction with RFX5 and RFXAP is essential for binding of the RFX complex to MHC-II promoters [8].
  • RFX1, -2 and -3 regulate expression of other medically important gene products (for example, interleukin-5 receptor alpha chain, IL-5R alpha) [9].
  • Regulatory factor X (RFX) proteins are transcriptional activators that recognize X-boxes (DNA of the sequence 5'-GTNRCC(0-3N)RGYAAC-3', where N is any nucleotide, R is a purine and Y is a pyrimidine) using a highly conserved 76-residue DNA-binding domain (DBD) [9].

Chemical compound and disease context of RFX1


Biological context of RFX1


Anatomical context of RFX1


Associations of RFX1 with chemical compounds


Physical interactions of RFX1


Enzymatic interactions of RFX1

  • RFX1 represses the unmethylated COL1A1 less efficiently than COL1A2 [22].

Regulatory relationships of RFX1

  • Our studies indicate that the regulatory factor for X-box (RFX) family proteins repress collagen alpha2(I) gene (COL1A2) expression (Xu, Y., Wang, L., Buttice, G., Sengupta, P. K., and Smith, B. D. (2003) J. Biol. Chem. 278, 49134-49144; Xu, Y., Wang, L., Buttice, G., Sengupta, P. K., and Smith, B. D. (2004) J. Biol. Chem. 279, 41319-41332) [16].

Other interactions of RFX1

  • In contrast to other mammalian RFX members that form dimers, RFX4 is revealed to have no distinct transcriptional activation domains [19].
  • The transcription start site of the collagen alpha2(1) gene (COL1A2) has a sequence-specific binding site for a DNA methylation-responsive binding protein called regulatory factor for X-box 1 (RFX1) (Sengupta, P. K., Erhlich, M., and Smith, B. D. (1999) J. Biol. Chem. 274, 36649-36655) [11].
  • Cotransfection studies indicated that RFX1, which is expressed ubiquitously, down-regulated the MAP1A 5' promoter activity in non-neuronal cells [12].
  • 3. These two regulatory genes are thus assigned to a region of high gene density and RFX1 is close to another DNA-binding factor, LYL1 [13].
  • Finally, both RFX1 and RFX5 are acetylated in vivo [16].
  • These results demonstrate that RFX1 mediates the immediate early response of the Id2 gene by serum stimulation and suggest that the function of RFX1 is regulated intramolecularly in its suppression in growth-arrested cells [23].

Analytical, diagnostic and therapeutic context of RFX1

  • In situ hybridization with 3H-labeled RFX1 cDNA has allowed us to identify two distinct targets on the short arm of chromosome 19 (19p13.1 and 19p13.2-p13.3) [13].
  • Functional analysis in cell culture demonstrated that a truncated version of RFX1 (*RFX1) lacking the repressor domain was able to activate transcription from B10.RRE [24].
  • When the TRAX1 complex was incubated with antibodies against a known recombinant X-box-binding protein, RFX1, and tested in electrophoretic mobility shift assays, TRAX1 was neither shifted nor blocked by the antibody [25].
  • To characterize this novel motif, we have performed a detailed dissection of the site-specific DNA binding activity of RFX1, a prototypical member of the RFX family [26].
  • Analytical ultracentrifugation (AUC) has demonstrated that RFX is a heterotrimer [27].


  1. RFX1, a transactivator of hepatitis B virus enhancer I, belongs to a novel family of homodimeric and heterodimeric DNA-binding proteins. Reith, W., Ucla, C., Barras, E., Gaud, A., Durand, B., Herrero-Sanchez, C., Kobr, M., Mach, B. Mol. Cell. Biol. (1994) [Pubmed]
  2. Identification of an epigenetically silenced gene, RFX1, in human glioma cells using restriction landmark genomic scanning. Ohashi, Y., Ueda, M., Kawase, T., Kawakami, Y., Toda, M. Oncogene (2004) [Pubmed]
  3. Assembly of functional regulatory complexes on MHC class II promoters in vivo. Fontes, J.D., Jabrane-Ferrat, N., Peterlin, B.M. J. Mol. Biol. (1997) [Pubmed]
  4. The RFX complex is crucial for the constitutive and CIITA-mediated transactivation of MHC class I and beta2-microglobulin genes. Gobin, S.J., Peijnenburg, A., van Eggermond, M., van Zutphen, M., van den Berg, R., van den Elsen, P.J. Immunity (1998) [Pubmed]
  5. The Epstein-Barr virus promoter initiating B-cell transformation is activated by RFX proteins and the B-cell-specific activator protein BSAP/Pax5. Tierney, R., Kirby, H., Nagra, J., Rickinson, A., Bell, A. J. Virol. (2000) [Pubmed]
  6. The bare lymphocyte syndrome and the regulation of MHC expression. Reith, W., Mach, B. Annu. Rev. Immunol. (2001) [Pubmed]
  7. Regulation of MHC class II genes: lessons from a disease. Mach, B., Steimle, V., Martinez-Soria, E., Reith, W. Annu. Rev. Immunol. (1996) [Pubmed]
  8. A gene encoding a novel RFX-associated transactivator is mutated in the majority of MHC class II deficiency patients. Masternak, K., Barras, E., Zufferey, M., Conrad, B., Corthals, G., Aebersold, R., Sanchez, J.C., Hochstrasser, D.F., Mach, B., Reith, W. Nat. Genet. (1998) [Pubmed]
  9. Structure of the winged-helix protein hRFX1 reveals a new mode of DNA binding. Gajiwala, K.S., Chen, H., Cornille, F., Roques, B.P., Reith, W., Mach, B., Burley, S.K. Nature (2000) [Pubmed]
  10. Dimeric RFX proteins contribute to the activity and lineage specificity of the interleukin-5 receptor alpha promoter through activation and repression domains. Iwama, A., Pan, J., Zhang, P., Reith, W., Mach, B., Tenen, D.G., Sun, Z. Mol. Cell. Biol. (1999) [Pubmed]
  11. The RFX family interacts at the collagen (COL1A2) start site and represses transcription. Sengupta, P.K., Fargo, J., Smith, B.D. J. Biol. Chem. (2002) [Pubmed]
  12. Role for RFX transcription factors in non-neuronal cell-specific inactivation of the microtubule-associated protein MAP1A promoter. Nakayama, A., Murakami, H., Maeyama, N., Yamashiro, N., Sakakibara, A., Mori, N., Takahashi, M. J. Biol. Chem. (2003) [Pubmed]
  13. The genes for MHC class II regulatory factors RFX1 and RFX2 are located on the short arm of chromosome 19. Pugliatti, L., Derré, J., Berger, R., Ucla, C., Reith, W., Mach, B. Genomics (1992) [Pubmed]
  14. Induction of Myc-intron-binding polypeptides MIBP1 and RFX1 during retinoic acid-mediated differentiation of haemopoietic cells. Zajac-Kaye, M., Ben-Baruch, N., Kastanos, E., Kaye, F.J., Allegra, C. Biochem. J. (2000) [Pubmed]
  15. Transcription factor RFX2 is abundant in rat testis and enriched in nuclei of primary spermatocytes where it appears to be required for transcription of the testis-specific histone H1t gene. Wolfe, S.A., van Wert, J., Grimes, S.R. J. Cell. Biochem. (2006) [Pubmed]
  16. Regulatory factor for X-box family proteins differentially interact with histone deacetylases to repress collagen alpha2(I) gene (COL1A2) expression. Xu, Y., Sengupta, P.K., Seto, E., Smith, B.D. J. Biol. Chem. (2006) [Pubmed]
  17. Regulatory Factor Interactions and Somatic Silencing of the Germ Cell-specific ALF Gene. Kim, M., Li, D., Cui, Y., Mueller, K., Chears, W.C., Dejong, J. J. Biol. Chem. (2006) [Pubmed]
  18. The transcriptional activation and repression domains of RFX1, a context-dependent regulator, can mutually neutralize their activities. Katan, Y., Agami, R., Shaul, Y. Nucleic Acids Res. (1997) [Pubmed]
  19. Human regulatory factor X 4 (RFX4) is a testis-specific dimeric DNA-binding protein that cooperates with other human RFX members. Morotomi-Yano, K., Yano, K., Saito, H., Sun, Z., Iwama, A., Miki, Y. J. Biol. Chem. (2002) [Pubmed]
  20. The S box of major histocompatibility complex class II promoters is a key determinant for recruitment of the transcriptional co-activator CIITA. Muhlethaler-Mottet, A., Krawczyk, M., Masternak, K., Spilianakis, C., Kretsovali, A., Papamatheakis, J., Reith, W. J. Biol. Chem. (2004) [Pubmed]
  21. Regulatory factor X, a bare lymphocyte syndrome transcription factor, is a multimeric phosphoprotein complex. Moreno, C.S., Rogers, E.M., Brown, J.A., Boss, J.M. J. Immunol. (1997) [Pubmed]
  22. Collagen alpha1(I) gene (COL1A1) is repressed by RFX family. Sengupta, P., Xu, Y., Wang, L., Widom, R., Smith, B.D. J. Biol. Chem. (2005) [Pubmed]
  23. RFX1 mediates the serum-induced immediate early response of Id2 gene expression. Wang, K.R., Nemoto, T., Yokota, Y. J. Biol. Chem. (2007) [Pubmed]
  24. Involvement of RFX proteins in transcriptional activation from a Ras-responsive enhancer element. Maijgren, S., Sur, I., Nilsson, M., Toftgård, R. Arch. Dermatol. Res. (2004) [Pubmed]
  25. Affinity enrichment and functional characterization of TRAX1, a novel transcription activator and X1-sequence-binding protein of HLA-DRA. Itoh-Lindstrom, Y., Peterlin, B.M., Ting, J.P. Mol. Cell. Biol. (1995) [Pubmed]
  26. A consensus motif in the RFX DNA binding domain and binding domain mutants with altered specificity. Emery, P., Strubin, M., Hofmann, K., Bucher, P., Mach, B., Reith, W. Mol. Cell. Biol. (1996) [Pubmed]
  27. Assembly of major histocompatability complex (MHC) class II transcription factors: association and promoter recognition of RFX proteins. Burd, A.L., Ingraham, R.H., Goldrick, S.E., Kroe, R.R., Crute, J.J., Grygon, C.A. Biochemistry (2004) [Pubmed]
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