title: Melanocyte-specific microphthalmia-associated transcription factor isoform activates its own gene promoter through physical interaction with lymphoid-enhancing factor 1.
abstract: Waardenburg syndrome type 2 (WS2) is associated with heterozygous mutations in the gene encoding microphthalmia-associated transcription factor (MITF) and characterized by deafness and hypopigmentation due to lack of melanocytes in the inner ear and skin. Melanocyte-specific MITF isoform (MITF-M) is essential for melanocyte differentiation and is transcriptionally induced by Wnt signaling that is mediated by beta-catenin and LEF-1. Here we show that MITF-M transactivates its own promoter (M promoter) by interacting with LEF-1, as judged by transient expression assays and in vitro protein-protein binding assays, whereas no transactivation of the M promoter was detected with MITF-M alone or with the combination of MITF-M and dominant-negative LEF1 that lacks the beta-catenin-binding domain. This synergy depends on the three LEF-1-binding sites that are clustered in the proximal M promoter. Importantly, MITF-M recruited on the M promoter could function as a non-DNA-binding cofactor for LEF-1. Thus, MITF-M may function as a self-regulator of its own expression to maintain a threshold level of MITF-M that is required for melanocyte development. We suggest that MITF-M haploinsufficiency may impair the dosage-sensitive role of MITF-M or the correct assembly of multiple transcription factors, involving MITF-M, on the M promoter, which could account for dominant inheritance of WS2.
authors.affiliation: Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980-8575, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Saito
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Yasumoto
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takeda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takahashi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukuzaki
authors.forename: Seiichi
authors.initials: S
authors.lastname: Orikasa
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibahara
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005799:Genes, Dominant; D006367:HeLa Cells; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051821:Lymphoid Enhancer-Binding Factor 1; D008544:Melanocytes / Q000378:metabolism*; D051739:Microphthalmia-Associated Transcription Factor; D008957:Models, Genetic; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; C497573:LEF1 protein, human; D051821:Lymphoid Enhancer-Binding Factor 1; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D020033:Protein Isoforms; D014157:Transcription Factors; D008156:Luciferases