Expression vector system comprising two selection markers

摘要: The invention pertains to an expression vector or a combination of at least two vectors comprising (a) polynucleotide encoding product interest insertion site for incorporating interest; (b) first selectable marker (sm I); (c) second II), which is different from the I), wherein activity I) II) partially influenced by other and markers are involved in folate metabolism. Also provided suitable host cells, selection methods producing polypeptides with high yield.