The Brn-2 transcription factor links activated BRAF to melanoma proliferation

Mol Cell Biol. 2004 Apr;24(7):2923-31. doi: 10.1128/MCB.24.7.2923-2931.2004.

Abstract

Malignant melanoma, an aggressive and increasingly common cancer, is characterized by a strikingly high rate (70%) of mutations in BRAF, a key component of the mitogen-activated protein (MAP) kinase signaling pathway. How signaling events downstream from BRAF affect the underlying program of gene expression is poorly understood. We show that the Brn-2 POU domain transcription factor is highly expressed in melanoma cell lines but not in melanocytes or melanoblasts and that overexpression of Brn-2 in melanocytes results in increased proliferation. Expression of Brn-2 is strongly upregulated by Ras and MAP kinase signaling. Importantly, the Brn-2 promoter is stimulated by kinase-activating BRAF mutants and endogenous Brn-2 expression is inhibited by RNA interference-mediated downregulation of BRAF. Moreover, silent interfering RNA-mediated depletion of Brn-2 in melanoma cells expressing activated BRAF leads to decreased proliferation. The results suggest that the high levels of Brn-2 expression observed in melanomas link BRAF signaling to increased proliferation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Down-Regulation
  • Gene Expression Regulation, Neoplastic
  • Homeodomain Proteins
  • Humans
  • MAP Kinase Signaling System / physiology
  • Melanocytes / cytology
  • Melanocytes / metabolism*
  • Melanoma / genetics
  • Melanoma / metabolism*
  • Melanoma / pathology
  • Mice
  • POU Domain Factors
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins c-raf / genetics
  • Proto-Oncogene Proteins c-raf / metabolism*
  • RNA, Small Interfering / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*

Substances

  • Homeodomain Proteins
  • POU Domain Factors
  • RNA, Small Interfering
  • Recombinant Fusion Proteins
  • Transcription Factors
  • transcription factor Brn-2
  • BRAF protein, human
  • Braf protein, mouse
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins c-raf