The RFX1 gene is a member of the regulatory factor X (RFX) gene family, which encodes transcription factors that contain five conserved domains including a highly conserved, centrally located, winged helix DNA binding domain as well as a dimerization domain located in the C-terminal region of the sequence. Apart from the five conserved domains, the RFX proteins diverge significantly. The DNA binding and dimerization domains of the RFX family proteins show no similarities to the other domains with the same functions in other proteins.
The RFX protein family is conserved in S. pombe, S. cerevisiae, C. elegans, mice and humans. There are seven known RFX proteins in humans, five in mice, and one in C. elegans as well as one in each of the two species of yeast.
The protein encoded by this gene is structurally related to regulatory factors X2, X3, X4, and X5. It is a transcriptional activator that can bind DNA as a monomer or as a heterodimer with RFX family members X2, X3, and X5, but not with X4. This protein binds to the Xboxes of MHC class II genes and is essential for their expression. Also, it can bind to an inverted repeat that is required for expression of hepatitis B virus genes. The RFX proteins were originally cloned and characterized due to their high affinity for a cis-acting promoter sequence, called the Xbox, found in all MHC class II genes.
Levels of mRNA encoding this protein as well as RFX2 and RFX3 are found to be consistently elevated in the testis and are variable in other tissues throughout the body.
RFX1 contains a C-terminal sequence with no apparent homology to other RFX proteins. This C-terminal tail contains an acidic region that is thought to aid in crossing the nuclear membrane. Two major functions are hypothesized to this exist for this domain: a contribution to the nuclear localization signal (NLS) as well as the contradictory down-regulation of DNA binding as well as nuclear association. These two functions were originally identified through sequence mutations and translational fusions with gfp (green fluorescent protein) and remain to be confirmed.
^Gajiwala KS, Chen H, Cornille F, Roques BP, Reith W, Mach B, Burley SK (2000). "Structure of the winged-helix protein hRFX1 reveals a new mode of DNA binding". Nature403 (6772): 916–921. doi:10.1038/35002634. PMID10706293.
^Pugliatti L, Derre J, Berger R, Ucla C, Reith W, Mach B (Sep 1992). "The genes for MHC class II regulatory factors RFX1 and RFX2 are located on the short arm of chromosome 19". Genomics13 (4): 1307–10. doi:10.1016/0888-7543(92)90052-T. PMID1505960.
^ abcAgami R, Shaul Y (April 1998). "The kinase activity of c-Abl but not v-Abl is potentiated by direct interaction with RFXI, a protein that binds the enhancers of several viruses and cell-cycle regulated genes". Oncogene16 (14): 1779–88. doi:10.1038/sj.onc.1201708. PMID9583676.
Reith W, Herrero-Sanchez C, Kobr M, et al. (1991). "MHC class II regulatory factor RFX has a novel DNA-binding domain and a functionally independent dimerization domain.". Genes Dev.4 (9): 1528–40. doi:10.1101/gad.4.9.1528. PMID2253877.
Sáfrány G, Perry RP (1993). "Transcription factor RFX1 helps control the promoter of the mouse ribosomal protein-encoding gene rpL30 by binding to its alpha element.". Gene132 (2): 279–83. doi:10.1016/0378-1119(93)90208-K. PMID8224874.
Doyle J, Hoffman S, Ucla C, et al. (1996). "Locations of human and mouse genes encoding the RFX1 and RFX2 transcription factor proteins.". Genomics35 (1): 227–30. doi:10.1006/geno.1996.0343. PMID8661125.
Katan-Khaykovich Y, Shaul Y (1998). "RFX1, a single DNA-binding protein with a split dimerization domain, generates alternative complexes.". J. Biol. Chem.273 (38): 24504–12. doi:10.1074/jbc.273.38.24504. PMID9733744.
Morotomi-Yano K, Yano K, Saito H, et al. (2002). "Human regulatory factor X 4 (RFX4) is a testis-specific dimeric DNA-binding protein that cooperates with other human RFX members.". J. Biol. Chem.277 (1): 836–42. doi:10.1074/jbc.M108638200. PMID11682486.
Sengupta PK, Fargo J, Smith BD (2002). "The RFX family interacts at the collagen (COL1A2) start site and represses transcription.". J. Biol. Chem.277 (28): 24926–37. doi:10.1074/jbc.M111712200. PMID11986307.
Nakayama A, Murakami H, Maeyama N, et al. (2003). "Role for RFX transcription factors in non-neuronal cell-specific inactivation of the microtubule-associated protein MAP1A promoter.". J. Biol. Chem.278 (1): 233–40. doi:10.1074/jbc.M209574200. PMID12411430.
Norquay LD, Yang X, Sheppard P, et al. (2003). "RFX1 and NF-1 associate with P sequences of the human growth hormone locus in pituitary chromatin.". Mol. Endocrinol.17 (6): 1027–38. doi:10.1210/me.2003-0025. PMID12624117.
Maijgren S, Sur I, Nilsson M, Toftgård R (2004). "Involvement of RFX proteins in transcriptional activation from a Ras-responsive enhancer element.". Arch. Dermatol. Res.295 (11): 482–9. doi:10.1007/s00403-004-0456-5. PMID15024578.