ADENYLOSUCCINATE SYNTHETASE - A DOMINANT AMPLIFIABLE GENETIC-MARKER IN MAMMALIAN-CELLS

Adenylosuccinate synthetase (AdSS) functions at the branchpoint of pur ine nucleotide metabolism leading to the synthesis of AMP. The enzyme is inhibited by a metabolite of alanosine, an aspartic acid analog tha t is highly cytotoxic for most cells. We show here that it is possible to use alanosine selection to isolate from a population of transforma nts those cells having the highest levels of AdSS activity resulting f rom uptake and expression of AdSS minigenes. Transformants isolated in this way were selected for resistance to even higher concentrations o f alanosine and resulted in the isolation of cells with highly amplifi ed copies of the transfected AdSS minigenes. We demonstrated that nons electable genes can be cotransferred and complified with AdSS minigene s. These findings indicate that AdSS minigenes can be used as dominant amplifiable genetic markers in mammalian cells.