Effects of gene dosage on the expression of human growth hormone cDNA in Escherichia coli

Abstract Gene dosage effects on the foreign protein production in Escherichia coli have been analyzed with the expression vectors containing one, two and four tandemly arranged human growth hormone cDNAs under various culture conditions. In a limited synthetic culture medium, a proportional relationship was observed between the number of the integrated cDNA and the amount of human growth hormone produced. With a culture medium rich in the nutrients, however, no such relationship was observed. These results suggest that, under the limited culture conditions, high-level expression of a foreign gene can be achieved by tandemly joined multiple copies of cDNA.