The her-2/neu oncogene stimulates the transcription of N-acetylglucosaminyltransferase V and expression of its cell surface oligosaccharide products.
Malignant transformation is associated with changes in the glycosylation of cell surface proteins. For example, the N-linked oligosaccharides containing the [GlcNAc beta(1,6)Man] branch are increased after transformation of many cell types by a number of tumor viruses and oncogenes which induce the expression of N-acetylglucosaminyl-transferase V (GlcNAc-T V), the enzyme that adds this branch. A large percentage of human breast carcinomas have increased N-linked beta(1,6) branches on glycoproteins, while up to 30% of breast carcinomas have amplified the oncogene her-2/neu (erb-B2). We tested the hypothesis that expression of her-2/neu stimulates GlcNAc-T V gene expression and increases the beta(1,6) branching of N-linked oligosaccharides. We found that neu-transformed NIH3T3 cells have a threefold increase in GlcNAc-T V enzyme activity and increased beta(1,6) branching on a specific set of glycoproteins. Promoter/reporter experiments showed that her-2/neu stimulates transcription from the human GlcNAc-T V promoter and that the her-2/neu response element was located about 400 bp 5' of the transcription initiation site and includes three Ets transcription factor binding sequences. Co-transfections with dominant-negative Raf and Ets expression plasmids demonstrated that the transcriptional activation of the GlcNAc-T V promoter by neu is mediated by the Ras-Raf-Ets signal transduction pathway.
Chen
L
L
Department of Biochemistry and Molecular Biology and Complex Carbohydrate Research Center, University of Georgia, Athens 30602, USA.
Zhang
W
W
Fregien
N
N
Pierce
M
M
D016475:3T3 Cells; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004268:DNA-Binding Proteins; D015971:Gene Expression Regulation, Enzymologic; D006023:Glycoproteins; D006801:Humans; D051379:Mice; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics* / Q000378:metabolism; D009844:Oligosaccharides / Q000096:biosynthesis*; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D006023:Glycoproteins; D017351:N-Acetylglucosaminyltransferases; D009844:Oligosaccharides; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras); D018719:Erb-b2 Receptor Tyrosine Kinases; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C107465:ERF protein, human; C494069:ETS2 protein, human; C494070:Ets2 protein, mouse; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase; C501009:HRAS protein, human