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Previous work has shown that melanoma cell lines express a distinct octamer binding protein. Given the role of octamer-binding proteins in cell differentiation and development, the role this factor is a key issue in understanding melanocyte differentiation and transformation. Using a proteolytic clipping assay, we show that the melanoma-specific octamer factor is Brn-2/N-Oct3, a POU domain protein previously known to be expressed in adult brain and in the developing nervous system. N-Oct3 mRNA was detected in a range of human melanoma cell lines and was around 10-fold elevated compared to normal human melanocytes while mRNA for Brn-2 was also detected in a mouse melanoblast cell line. Expression of Brn-2/N-Oct3, in melanoma cells in cotransfection assays activated the expression of the MHC class II DR alpha promoter but repressed the activity of the melanocyte-specific tyrosinase promoter. Repression correlated with Brn-2/N-Oct3 binding in a mutually exclusive fashion with basic-helix-loop-helix-leucine-zipper (bHLH-LZ) transcription factor USF in vitro and with Brn-2 expression preventing activation of the tyrosinase promoter by the bHLH-LZ factor Microphthalmia in vivo. The potential role of Brn-2/N-Oct3 in melanocyte differentiation and gene expression is discussed.


Journal article



Publication Date





2157 - 2164


Eukaryotic Transcription Laboratory, Marie Curie Research Institute, Oxted, Surrey, UK.


Tumor Cells, Cultured, Melanocytes, Humans, Melanoma, Monophenol Monooxygenase, Homeodomain Proteins, Neoplasm Proteins, Transcription Factors, DNA, Neoplasm, RNA, Messenger, Antigens, Neoplasm, HLA-DR Antigens, Transfection, Gene Expression Regulation, Gene Expression Regulation, Neoplastic, Binding Sites, Base Sequence, Helix-Loop-Helix Motifs, Molecular Sequence Data, POU Domain Factors, Promoter Regions, Genetic, Melanoma-Specific Antigens