The microphthalmia-associated transcription factor requires SWI/SNF enzymes to activate melanocyte-specific genes.
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.
de la Serna
Ivana L
IL
Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA. idelaserna@meduohio.edu
Ohkawa
Yasuyuki
Y
Higashi
Chiduru
C
Dutta
Chaitali
C
Osias
Jules
J
Kommajosyula
Naveen
N
Tachibana
Taro
T
Imbalzano
Anthony N
AN
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
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