Heterogeneous SWI/SNF chromatin remodeling complexes promote expression of microphthalmia-associated transcription factor target genes in melanoma.

ABSTRACT: The microphthalmia-associated transcription factor (MITF) promotes melanocyte differentiation and cell-cycle arrest. Paradoxically, MITF also promotes melanoma survival and proliferation, acting like a lineage survival oncogene. Thus, it is critically important to understand the mechanisms that regulate MITF activity in melanoma cells. SWI/SNF chromatin remodeling enzymes are multiprotein complexes composed of one of two related ATPases, BRG1 or BRM, and 9-12-associated factors (BAFs). We previously determined that BRG1 interacts with MITF to promote melanocyte differentiation. However, it was unclear whether SWI/SNF enzymes regulate the expression of different classes of MITF target genes in melanoma. In this study, we characterized SWI/SNF subunit expression in melanoma cells and observed downregulation of BRG1 or BRM, but not concomitant loss of both ATPases. Re-introduction of BRG1 in BRG1-deficient SK-MEL5 cells enhanced expression of differentiation-specific MITF target genes and resistance to cisplatin. Downregulation of the single ATPase, BRM, in SK-MEL5 cells inhibited expression of both differentiation-specific and pro-proliferative MITF target genes and inhibited tumorigenicity in vitro. Our data suggest that heterogeneous SWI/SNF complexes composed of either the BRG1 or BRM subunit promote expression of distinct and overlapping MITF target genes and that at least one ATPase is required for melanoma tumorigenicity.

SUBMITTER: Keenen B 

PROVIDER: S-EPMC2803337 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature