Expression vector enabling screening of cells with high expression of recombinant protein, transformant with high expression of recombinant protein and utilization thereof

摘要

The present invention relates to an expression vector which comprises an expression unit containing a first selective marker gene and an expression unit containing a second selective marker gene which differs from the first selective marker gene; a transformant having the expression vector; a method for screening cells which express high level of a recombinant protein by use of the transformant; and the like. The present invention provides a transformant which expresses high level of a target protein, in particular an expression vector which can reproducibly and efficiently screen a highly productive strains of cultured animal cells.