Induction of N-acetylglucosaminyltransferase V by elevated expression of activated or proto-Ha-ras oncogenes.

Viral infection of cultured cells with transforming viruses causes an increase in cell-surface N-linked beta 1-6 (GlcNAc beta 1-6Man) branching of complex-type oligosaccharides. Similar observations have been made after transfection of cells with activated oncogenes, which is associated with an induction of tumorigenic and metastatic properties. In this study, the effects of transfection of both activated and proto-Ha-ras oncogenes into NIH3T3 cells were analyzed. The results showed that, in comparison with NIH3T3 cells, both ras transfectants have increased sensitivity to the cytotoxic action of L-PHA. An increase in beta 1-6 branching and an increased level of N-acetylglucosaminyltransferase V (GlcNAc-T V), the enzyme which initiates the beta 1-6 branching were also observed. The levels of GlcNAc-T I and beta 1-4 Gal-T remained unchanged in activated Ha-ras transfected NIH3T3 cells. These data suggest that a specific induction of GlcNAc-T V occurs after transfection with either the proto- or activated Ha-ras oncogenes, which is responsible for the increased beta 1-6 branching previously observed.