Abstract
Oncogenic transformation of fibroblasts by the src oncogene has long been known to cause an increase in the size of cell-surface protein-bound oligosaccharides, owing primarily to increased N-glycan branching mediated by increased beta-1,6-N-acetylglucosaminyltransferase V (GnT V) activity. The src-responsive element of the GnT V promoter was localized to Ets-binding sites and the promoter was transcriptionally stimulated by both ets-1 and ets-2 expression [Buckhaults, Chen, Fregien and Pierce (1997) J. Biol. Chem. 272, 19575-19581; Kang, Saito, Ihara, Miyoshi, Koyama, Sheng and Taniguchi (1996) J. Biol. Chem. 271, 26706-26712]. Because GnT V action requires the prior action of beta-1,2-N-acetylglucosaminyltransferase II (GnT II) and the human GnT II promoter contains four putative Ets-binding sites [Chen, Zhou, Tan and Schachter (1998) Glycoconj. J. 15, 301-308], GnT II might also be under oncogenic control via Ets transcription factors. We now report that co-transfection into HepG2 or COS-1 cells of either ets-1 or ets-2 expression plasmids together with chimaeric GnT II promoter-chloramphenicol acetyltransferase plasmids results in a 2-4-fold stimulation of promoter activity. Mobility-shift assays and South-Western blots localized the functional Ets-binding site to one of the four putative sites on the GnT II promoter. The GnT II promoter, unlike the GnT V promoter, is not activated by either src or neu. Therefore although both promoters are stimulated by a member of the Ets family of transcription factors, the functional role of this Ets transcriptional control seems to be different for the two genes.