MafF is one of the small Maf proteins, which are basic region and basic leucine zipper (bZIP)-type transcription factors. The HUGO Gene Nomenclature Committee-approved gene name of MAFF is “v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog F”.
MafF was first cloned and identified in chicken in 1993 as a member of the small Maf (sMaf) genes.[1] MAFF has been identified in many vertebrates, including humans.[2] There are three functionally redundant sMaf proteins in vertebrates, MafF, MafG, and MafK.
Structure
MafF has a bZIP structure that consists of a basic region for DNA binding and a leucine zipper structure for dimer formation.[1] Similar to other sMafs, MafF lacks any canonical transcriptional activation domains.[1]
Expression
MAFF is broadly but differentially expressed in various tissues. MAFF expression was detected in all 16 tissues examined by the human BodyMap Project, but relatively abundant in adipose, colon, lung, prostate and skeletal muscle tissues.[3] Human MAFF gene is induced by proinflammatory cytokines, interleukin 1 beta and tumor necrosis factor in myometrial cells.[4]
Function
Because of sequence similarity, no functional differences have been observed among the sMafs in terms of their bZIP structures. sMafs form homodimers by themselves and heterodimers with other specific bZIP transcription factors, such as CNC (cap 'n' collar) proteins [p45 NF-E2 (NFE2), Nrf1 (NFE2L1), Nrf2 (NFE2L2), and Nrf3 (NFE2L3)][5][6][7][8] and Bach proteins (BACH1 and BACH2).[9]
Target genes
sMafs regulate different target genes depending on their partners. For instance, the p45-NF-E2-sMaf heterodimer regulate genes responsible for platelet production.[5][10][11] Nrf2-sMaf heterodimer regulates a battery of cytoprotective genes, such as antioxidant/xenobiotic metabolizing enzyme genes.[7][12] The Bach1-sMaf heterodimer regulates the heme oxygenase-1 gene.[9] In particular, it has been reported that MafF regulates the oxytocin receptor gene.[13] The contribution of individual sMafs to the transcriptional regulation of their target genes has not yet been well examined.
Disease linkage
Loss of sMafs results in disease-like phenotypes as summarized in table below. Mice lacking MafF are seemingly healthy under laboratory conditions.[14] However, mice lacking MafG exhibit mild neuronal phenotype and mild thrombocytopenia,[15] mice lacking Mafg and one allele of Mafk (Mafg−/−::Mafk+/−) exhibit progressive neuronal degeneration, thrombocytopenia and cataract,[16][17] and mice lacking MafG and MafK (Mafg−/−::Mafk−/−) exhibit more severe neuronal degeneration and die in the perinatal stage.[18] Mice lacking MafF, MafG and MafK are embryonic lethal, demonstrating that MafF is indispensable for embryonic development.[19] Embryonic fibroblasts that are derived from Maff−/−::Mafg-/−::Mafk−/− mice fail to activate Nrf2-dependent cytoprotective genes in response to stress.[12]
Genotype
Mouse Phenotype
Maff
Mafg
Mafk
−/−
No apparent phenotype under laboratory conditions [14]
In addition, accumulating evidence suggests that as partners of CNC and Bach proteins, sMafs are involved in the onset and progression of various human diseases, including neurodegeneration, arteriosclerosis and cancer.
↑Massrieh W, Derjuga A, Doualla-Bell F, Ku CY, Sanborn BM, Blank V (Apr 2006). "Regulation of the MAFF transcription factor by proinflammatory cytokines in myometrial cells". Biology of Reproduction. 74 (4): 699–705. doi:10.1095/biolreprod.105.045450. PMID16371591.
↑ 5.05.1Igarashi K, Kataoka K, Itoh K, Hayashi N, Nishizawa M, Yamamoto M (Feb 1994). "Regulation of transcription by dimerization of erythroid factor NF-E2 p45 with small Maf proteins". Nature. 367 (6463): 568–72. doi:10.1038/367568a0. PMID8107826.
↑ 7.07.1Itoh K, Chiba T, Takahashi S, Ishii T, Igarashi K, Katoh Y, Oyake T, Hayashi N, Satoh K, Hatayama I, Yamamoto M, Nabeshima Y (Jul 1997). "An Nrf2/small Maf heterodimer mediates the induction of phase II detoxifying enzyme genes through antioxidant response elements". Biochemical and Biophysical Research Communications. 236 (2): 313–22. doi:10.1006/bbrc.1997.6943. PMID9240432.
↑Kobayashi A, Ito E, Toki T, Kogame K, Takahashi S, Igarashi K, Hayashi N, Yamamoto M (Mar 1999). "Molecular cloning and functional characterization of a new Cap'n' collar family transcription factor Nrf3". The Journal of Biological Chemistry. 274 (10): 6443–52. doi:10.1074/jbc.274.10.6443. PMID10037736.
↑Shivdasani RA, Rosenblatt MF, Zucker-Franklin D, Jackson CW, Hunt P, Saris CJ, Orkin SH (Jun 1995). "Transcription factor NF-E2 is required for platelet formation independent of the actions of thrombopoietin/MGDF in megakaryocyte development". Cell. 81 (5): 695–704. doi:10.1016/0092-8674(95)90531-6. PMID7774011.
↑Kimura T, Ivell R, Rust W, Mizumoto Y, Ogita K, Kusui C, Matsumura Y, Azuma C, Murata Y (Oct 1999). "Molecular cloning of a human MafF homologue, which specifically binds to the oxytocin receptor gene in term myometrium". Biochemical and Biophysical Research Communications. 264 (1): 86–92. doi:10.1006/bbrc.1999.1487. PMID10527846.
↑ 14.014.1Onodera K, Shavit JA, Motohashi H, Katsuoka F, Akasaka JE, Engel JD, Yamamoto M (Jul 1999). "Characterization of the murine mafF gene". The Journal of Biological Chemistry. 274 (30): 21162–9. doi:10.1074/jbc.274.30.21162. PMID10409670.
Ye X, Li Y, Huang Q, Yu Y, Yuan H, Wang P, Wan D, Gu J, Huo K, Li YY, Lu H (May 2006). "The novel human gene MIP functions as a co-activator of hMafF". Archives of Biochemistry and Biophysics. 449 (1–2): 87–93. doi:10.1016/j.abb.2006.02.011. PMID16549056.
Massrieh W, Derjuga A, Doualla-Bell F, Ku CY, Sanborn BM, Blank V (Apr 2006). "Regulation of the MAFF transcription factor by proinflammatory cytokines in myometrial cells". Biology of Reproduction. 74 (4): 699–705. doi:10.1095/biolreprod.105.045450. PMID16371591.
Marini MG, Asunis I, Chan K, Chan JY, Kan YW, Porcu L, Cao A, Moi P (2003). "Cloning MafF by recognition site screening with the NFE2 tandem repeat of HS2: analysis of its role in globin and GCSl genes regulation". Blood Cells, Molecules & Diseases. 29 (2): 145–58. doi:10.1006/bcmd.2002.0550. PMID12490281.
Kataoka K, Yoshitomo-Nakagawa K, Shioda S, Nishizawa M (Jan 2001). "A set of Hox proteins interact with the Maf oncoprotein to inhibit its DNA binding, transactivation, and transforming activities". The Journal of Biological Chemistry. 276 (1): 819–26. doi:10.1074/jbc.M007643200. PMID11036080.
Kimura T, Ivell R, Rust W, Mizumoto Y, Ogita K, Kusui C, Matsumura Y, Azuma C, Murata Y (Oct 1999). "Molecular cloning of a human MafF homologue, which specifically binds to the oxytocin receptor gene in term myometrium". Biochemical and Biophysical Research Communications. 264 (1): 86–92. doi:10.1006/bbrc.1999.1487. PMID10527846.
Igarashi K, Kataoka K, Itoh K, Hayashi N, Nishizawa M, Yamamoto M (Feb 1994). "Regulation of transcription by dimerization of erythroid factor NF-E2 p45 with small Maf proteins". Nature. 367 (6463): 568–72. doi:10.1038/367568a0. PMID8107826.
