Development of Double Copy Dicistronic Retroviral Vectors for Transfer and Expression of Glycosyltransferase Genes
Glycosylation of secretory and cell surface proteins is a multistep enzymatic process which takes place on the endoplasmic reticulum and in the Golgi complex, and involves series of highly specific glycosyltransferases and glycosidases (Kornfeld and Kornfeld, 1985). Control of the relative activities of these enzymes is one of the mechanisms regulating pattern of glycosylation of end-products of protein biosynthesis. Number of groups have demonstrated that cell clones lacking or displaying high activity of particular enzymes glycosytate the same protein differently. Indeed number of hereditary diseases linked to the impaired glycosylation mechanisms due to the lack or low expression of glycosylating enzyme genes was described (Jacken et al. 1994). Moreover, overexpression or knockout of genes encoding number of glycosyltransferases caused altered protein glycosylation in various experimental models (Gorelik et al. 1995, Yoshimura et al. 1995, 1996). Genetic modification of cells leading to changes in the glycan structures is more often referred to as genetic sugar engineering. On the other hand cells displaying defects in particular enzyme gene expression may be corrected by insertion of functional gene. Such procedure is referred to as gene therapy (Friedmann, 1992).
KeywordsInternal Promoter Murine Melanoma Cell Double Copy Internal Ribosome Entry Site Element Cell Surface Carbohydrate
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