6fx5
MITF dimerization mutantMITF dimerization mutant
Structural highlights
Disease[MITF_MOUSE] Defects in Mitf are the cause of microphthalmia (mi), a condition characterized by loss of pigmentation; reduced eye size; failure of secondary bone resorption; reduced numbers of mast cells; early onset of deafness, and which gives rise to a number of different phenotypes. Among them, microphthalmia-eyeless white (mi-ew) has a normal appearance at the heterozygous state, but shows white coat; eyes almost absent and eyelids never open at homozygosity. Microphthalmia-black and white spot (mi-bws) is normal at heterozygosity, and presents white spots and black eyes at homozygous state. Microphthalmia-white (mi-wh) has reduced coat color and eye pigmentation; spots on toes, tail and belly; inner ear defects at heterozygosity, and at homozygosity shows white coat; eyes small and inner iris slightly pigmented; spinal ganglia, adrenal medulla and dermis smaller than normal, and inner ear defects. Microphthalmia-vitiligo (mi-vi) has normal phenotype at heterozygosity, but shows gradual depigmentation of coat, skin and eyes; and retinal degeneration at homozygosity. Microphthalmia-spotted (mi-sp) shows normal phenotype; at homozygosity, however, tyrosinase activity in skin is reduced. Microphthalmia-defective irism (mi-di) has reduced retinal pigmentation at heterozygosity and shows white coat; eyes of reduced sized and possible mild osteoporosis at homozygosity. Microphthalmia-cloudy eyed (mi-ce) has a normal appearance at the heterozygous state, but shows white coat; eyes of reduced size and unpigmented at homozygosity. Microphthalmia-red-eyed white (mi-rw) has a normal appearance at the homozygous state, but shows white coat with one or more pigmented spots around the head/and or tail; eyes are small and red at heterozygosity. Microphthalmia-black-eyed white (mi-bw) shows a white coat but normal sized eyes which reamin black at homozygosity. Function[MITF_MOUSE] Transcription factor that regulates the expression of genes with essential roles in cell differentiation, proliferation and survival. Binds to symmetrical DNA sequences (E-boxes) (5'-CACGTG-3') found in the promoters of target genes, such as BCL2 and tyrosinase (TYR). Plays an important role in melanocyte development by regulating the expression of tyrosinase (TYR) and tyrosinase-related protein 1 (TYRP1). Plays a critical role in the differentiation of various cell types, such as neural crest-derived melanocytes, mast cells, osteoclasts and optic cup-derived retinal pigment epithelium. Publication Abstract from PubMedInterrupted dimeric coiled coil segments are found in a broad range of proteins and generally confer selective functional properties such as binding to specific ligands. However, there is only one documented case of a basic-helix-loop-helix leucine zipper transcription factor-microphthalmia-associated transcription factor (MITF)-in which an insertion of a three-residue stammer serves as a determinant of conditional partner selectivity. To unravel the molecular principles of this selectivity, we have analyzed the high-resolution structures of stammer-containing MITF and an engineered stammer-less MITF variant, which comprises an uninterrupted symmetric coiled coil. Despite this fundamental difference, both MITF structures reveal identical flanking in-phase coiled coil arrangements, gained by helical over-winding and local asymmetry in wild-type MITF across the stammer region. These conserved structural properties allow the maintenance of a proper functional readout in terms of nuclear localization and binding to specific DNA-response motifs regardless of the presence of the stammer. By contrast, MITF heterodimer formation with other bHLH-Zip transcription factors is only permissive when both factors contain either the same type of inserted stammer or no insert. Our data illustrate a unique principle of conditional partner selectivity within the wide arsenal of transcription factors with specific partner-dependent functional readouts. Mechanism of conditional partner selectivity in MITF/TFE family transcription factors with a conserved coiled coil stammer motif.,Pogenberg V, Ballesteros-Alvarez J, Schober R, Sigvaldadottir I, Obarska-Kosinska A, Milewski M, Schindl R, Ogmundsdottir MH, Steingrimsson E, Wilmanns M Nucleic Acids Res. 2019 Nov 28. pii: 5644993. doi: 10.1093/nar/gkz1104. PMID:31777941[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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