Gene amplification and high-level expression of human pro-urokinase cDNA in Chinese hamster ovary cells.

ABSTRACT

Human Pro-Urokinase (Pro-UK) is expressed in CHO-DHFR- cells at high efficiency by co-transfecting the mouse dhfr gene and Pro-UK cDNA under the control of the SV40 late promoter. After gene co-amplification, the product level could reach 2-3 micrograms/10(6) cells/24 h in the presence of 5 x 10(-6) mol/L MTX, and the levels can be further raised to 3.5-4 micrograms/10(6) cells/24 h by PMA superinduction. The copy number of Pro-UK cDNA in the genomes of host cells is about 200-300 copies/cell. The Western blot analysis shows that the recombinant Pro-UK has similar molecular weight to its natural counterpart, and also the amidolytic activity of the product is determined by S-2444 assay.