[Constitutive expression of human fibroblast interferon gene controlled by SV40 early promoter in CHO cells]

HindII fragment encoding human fibroblast interferon (IFN beta) gene coding sequence was fused at 60 bp downstream from the RNA start site of SV40 early gene to be a constitutive expression plasmid pSVE beta. This recombinant plasmid was transfected into the dihydrofolate reductase (dhfr)-deficient Chinese hamster ovary (CHO) cells together with a selectable dhfr gene. About half of transformants continuously secreted IFN beta into the supernatant without inducement. One of the subclone transformants constitutively produced up to 852U IFN beta/2 X 10(6) cells/ml. 48hr in common medium.