title: MITF links differentiation with cell cycle arrest in melanocytes by transcriptional activation of INK4A.
abstract: Cell cycle exit is required for proper differentiation in most cells and is critical for normal development, tissue homeostasis, and tumor suppression. However, the mechanisms that link cell cycle exit with differentiation remain poorly understood. Here, we show that the master melanocyte differentiation factor, microphthalmia transcription factor (MITF), regulates cell cycle exit by activating the cell cycle inhibitor INK4A, a tumor suppressor that frequently is mutated in melanomas. MITF binds the INK4A promoter, activates p16(Ink4a) mRNA and protein expression, and induces retinoblastoma protein hypophosphorylation, thereby triggering cell cycle arrest. This activation of INK4A was required for efficient melanocyte differentiation. Interestingly, MITF was also required for maintaining INK4A expression in mature melanocytes, creating a selective pressure to escape growth inhibition by inactivating INK4A. These findings demonstrate that INK4A can be regulated by a differentiation factor, establish a mechanistic link between melanocyte differentiation and cell cycle exit, and potentially explain the tissue-specific tendency for INK4A mutations to occur in melanoma.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Loercher
authors.forename: Elizabeth M H
authors.initials: EM
authors.lastname: Tank
authors.forename: Rachel B
authors.initials: RB
authors.lastname: Delston
authors.forename: J William
authors.initials: JW
authors.lastname: Harbour
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D020868:Gene Silencing; D006801:Humans; D008544:Melanocytes / Q000166:cytology / Q000502:physiology*; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D016160:Retinoblastoma Protein; D014157:Transcription Factors