title: The microphthalmia-associated transcription factor requires SWI/SNF enzymes to activate melanocyte-specific genes.
abstract: The microphthalmia transcription factor (Mitf) activates melanocyte-specific gene expression, is critical for survival and proliferation of melanocytes during development, and has been described as an oncogene in malignant melanoma. SWI/SNF complexes are ATP-dependent chromatin-remodeling enzymes that play a role in many developmental processes. To determine the requirement for SWI/SNF enzymes in melanocyte differentiation, we introduced Mitf into fibroblasts that inducibly express dominant negative versions of the SWI/SNF ATPases, Brahma or Brahma-related gene 1 (BRG1). These dominant negative SWI/SNF components have been shown to inhibit gene activation events that normally require SWI/SNF enzymes. We found that Mitf-mediated activation of a subset of endogenous melanocyte-specific genes required SWI/SNF enzymes but that cell-cycle regulation occurred independently of SWI/SNF function. Activation of tyrosinase-related protein 1, a melanocyte-specific gene, correlated with SWI/SNF-dependent changes in chromatin accessibility at the endogenous locus. Both BRG1 and Mitf could be localized to the tyrosinase-related protein 1 and tyrosinase promoters by chromatin immunoprecipitation, whereas immunofluorescence and immunoprecipitation experiments indicate that Mitf and BRG1 co-localized in the nucleus and physically interacted. Together these results suggest that Mitf can recruit SWI/SNF enzymes to melanocyte-specific promoters for the activation of gene expression via induced changes in chromatin structure at endogenous loci.
authors.affiliation: Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA. idelaserna@meduohio.edu
authors.forename: Ivana L
authors.initials: IL
authors.lastname: de la Serna
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ohkawa
authors.forename: Chiduru
authors.initials: C
authors.lastname: Higashi
authors.forename: Chaitali
authors.initials: C
authors.lastname: Dutta
authors.forename: Jules
authors.initials: J
authors.lastname: Osias
authors.forename: Naveen
authors.initials: N
authors.lastname: Kommajosyula
authors.forename: Taro
authors.initials: T
authors.lastname: Tachibana
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Imbalzano
mesh_terms: D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D017931:DNA Primers; D005434:Flow Cytometry; D005784:Gene Amplification; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008544:Melanocytes / Q000502:physiology*; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D017931:DNA Primers; D051739:Microphthalmia-Associated Transcription Factor; C445179:SWI-SNF-B chromatin-remodeling complex; D014157:Transcription Factors