Correct evaluation of reporter assays in different cell lines by direct determination of the introduced plasmid amount

Transfection efficiency in reporter gene assays is usually determined by co transfection of a reference reporter gene under the control of a constituti vely active strong promoter and determination of the reference enzyme activ ity. The SV40 promoter-driven beta-galactosidase reporter plasmid is freque ntly used as the reference reporter plasmid, Here we show that the beta-gal actosidase expression in different cell lines does not correctly reflect th e amount of plasmid taken up by cells and thus is not an accurate measure o f transfection efficiency. The direct determination of introduced plasmid c oncentration in Lysates of transfected cells is suitable for monitoring the transfection efficiency in reporter gene assays even if different cell lin es are compared.