CHARACTERIZATION OF A HUMAN GLYCOPROTEIN (ERYTHROPOIETIN) PRODUCED INCULTURED TOBACCO CELLS

Erythropoietin (Epo), a glycoprotein that regulates the formation of e rythrocytes in mammals, was produced in cultured tobacco BY2 cells (Ni cotiana tabacum L. cv. Bright Yellow 2) by introducing human Epo cDNA via Agrobacterium tumefaciens-mediated gene transfer. Epo was correctl y processed and subsequently penetrated the plasma membrane of tobacco cells. However, it remained attached to the cell wall and was not rel eased into the culture medium. Although Epo produced by tobacco cells was glycosylated with N-linked oligosaccharides, these carbohydrates w ere smaller than those of the recombinant Epo produced in mammalian ce lls. Epo produced in tobacco exhibited in vitro biological activities by inducing the differentiation and proliferation of erythroid cells. However, it had no in vivo biological activities. A lectin-binding ass ay indicated the lack of sialic acid residues in the N-linked oligosac charides of Epo, suggesting that Epo was removed from the circulation before it reached erythropoietic tissues.