摘要 |
An improved vector for introducing a DNA coding sequence for a heterologous protein into a mammalian cell line to increase protein expression. The vector comprises a cDNA protein coding sequence, a first promoter and a downstream donor intron, the first promoter and downstream donor intron being located between a second promoter and a donor intron acceptor. In an illustrative example, the sequence codes for Factor VIII and high productivity of a transfected cell line is assured by establishing a minimum amplifiability index which, contrary to current practice, focuses on using cell lines having relatively low productivity prior to amplification. |