WS5, a direct target of oncogenic transcription factor Myc, is related to human melanoma glycoprotein genes and has oncogenic potential.
We have isolated a gene (WS5) that is specifically expressed at the mRNA and protein level in avian fibroblasts transformed by the v-myc oncogene of avian acute leukemia virus MC29. In a conditional cell transformation system, WS5 gene expression was tightly correlated with v-myc activation. The WS5 gene contains 11 exons, encoding a 733-amino acid protein with a transmembrane region and a polycystic kidney disease (PKD) domain. Near the transcriptional start site, the WS5 promoter contains a cluster of four binding sites for the Myc-Max complex and a binding site for transcription factor C/EBPalpha. Electrophoretic mobility shift assays and chromatin immunoprecipitation showed that Myc, Max and C/EBPalpha bind specifically to these sites. Functional promoter analyses revealed that both the Myc-binding site cluster and the C/EBPalpha-binding site are essential for strong transcriptional activation, and that Myc and C/EBPalpha synergistically activate the WS5 promoter. Ectopic expression of WS5 led to cell transformation documented by anchorage-independent growth. The human melanoma antigen Pmel17, a type I transmembrane glycoprotein, is the mammalian protein with the highest amino acid sequence identity (38%) to WS5. The Pmel17 gene is regulated by the MITF protein, a bHLHZip transcription factor with DNA binding specificities similar to those of Myc/Max. WS5 is also related to human glycoprotein GPNMB expressed in metastatic melanoma cells and implicated in the progression of brain and liver tumors.
Reiter
F
F
Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
Hartl
M
M
Karagiannidis
A I
AI
Bister
K
K
D000595:Amino Acid Sequence; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D008545:Melanoma / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
D022763:CCAAT-Enhancer-Binding Protein-alpha; D006023:Glycoproteins; D008565:Membrane Proteins; D015513:Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc