SWI/SNF chromatin remodeling complex is critical for the expression of microphthalmia-associated transcription factor in melanoma cells.
The microphthalmia-associated transcription factor (MITF) is required for melanocyte development, maintenance of the melanocyte-specific transcription, and survival of melanoma cells. MITF positively regulates expression of more than 25 genes in pigment cells. Recently, it has been demonstrated that expression of several MITF downstream targets requires the SWI/SNF chromatin remodeling complex, which contains one of the two catalytic subunits, Brm or Brg1. Here we show that the expression of MITF itself critically requires active SWI/SNF. In several Brm/Brg1-expressing melanoma cell lines, knockdown of Brg1 severely compromised MITF expression with a concomitant downregulation of MITF targets and decreased cell proliferation. Although Brm was able to substitute for Brg1 in maintaining MITF expression and melanoma cell proliferation, sequential knockdown of both Brm and Brg1 in 501mel cells abolished proliferation. In Brg1-null SK-MEL-5 melanoma cells, depletion of Brm alone was sufficient to abrogate MITF expression and cell proliferation. Chromatin immunoprecipitation confirmed the binding of Brg1 or Brm to the promoter of MITF. Together these results demonstrate the essential role of SWI/SNF for expression of MITF and suggest that SWI/SNF may be a promissing target in melanoma therapy.
Vachtenheim
Jiri
J
Laboratory of Molecular Biology, University Hospital, Charles University, Prague, Czech Republic. jivach@upn.anet.cz
Ondrusová
Lubica
L
Borovanský
Jan
J
D045744:Cell Line, Tumor; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047468:Immunoprecipitation; D008545:Melanoma / Q000235:genetics*; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D002868:Chromosomal Proteins, Non-Histone; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D009687:Nuclear Proteins; C084011:SMARCA2 protein, human; C445179:SWI-SNF-B chromatin-remodeling complex; D014157:Transcription Factors; C084108:SMARCA4 protein, human; D004265:DNA Helicases