Method of expressing recombinant protein in cho cells

Abstract

Method for enhancing the transfection rate of a mammalian expression vector in CHO cells.

1 . A method for enhancing the transfection rate of a mammalian expression vector in CHO cells by
 transfecting the cells with an expression vector that comprises a transcription unit for a product gene, which transcription unit is under control of the mCMV promoter, and a second transcription unit comprising a glutamine synthetase (GS) marker gene   transferring the cells in a glutamine-free culture medium supplemented with methionine sulfoxime for selection of the GS marker   counting of transfectants after incubation in order to determine the transfection rate and   comparing the transfection rate with the transfection rate of an identical expression vector having a different promoter in the first transcription unit.   
     
     
         2 . The method according to  claim 1 , characterized in that the mCMV promoter comprises the natural transcription start site (+0) and extends upstream to position −500. 
     
     
         3 . The method according to  claim 2 , characterized in that the mCMV promoter extends to the natural Xho I restriction site. 
     
     
         4 . The method according to  claim 1 , characterized in that the mCMV promoter lacks the first, natural intron of the mCMV promoter.