THE HER-2 NEU ONCOGENE STIMULATES THE TRANSCRIPTION OF N-ACETYLGLUCOSAMINYLTRANSFERASE-V AND EXPRESSION OF ITS CELL-SURFACE OLIGOSACCHARIDEPRODUCTS/

Malignant transformation is associated with changes in the glycosylati on of cell surface proteins. For example, the N-linked oligosaccharide s containing the [GlcNAc beta(1,6)Man] branch are increased after tran sformation of many cell types by a number of tumor viruses and oncogen es which induce the expression of N-acetylglucosaminyl-transferase V ( GlcNAc-T V), the enzyme that adds this branch, A large percentage of h uman breast carcinomas have increased N-linked beta(1,6) branches on g lycoproteins, 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 b eta(1,6) branching of N-linked oligosaccharides, We found that neu-tra nsformed NIH3T3 cells have a threefold increase in GlcNAc-T V enzyme a ctivity and increased beta(1,6) branching on a specific set of glycopr oteins. Promoter/reporter experiments showed that her-2/neu stimulates transcription from the human GlcNAc-T V promoter and that the her-2/n eu response element was located about 400 bp 5' of the transcription i nitiation site and includes three Ets transcription factor binding seq uences, Co-transfections with dominant-negative Raf and Ets expression plasmids demonstrated that the transcriptional activation of the GlcN Ac-T V promoter by neu is mediated by the Ras-Raf-Ets signal transduct ion pathway.