A stable vector for high-level expression and secretion of human interferon alpha A in yeast

Yeast high stable plasmid vector pHC11 was constructed by introducing pEM-BL Yi27 cleaved with SmaI into the SnaBI site of intact 2 microns plasmid. The result of plasmid stability assay revealed that 82% of the host cells still harbored the vector after 50-generations growth in non-selective medium, which confirmed the existence of a non-functional region in 2 microns plasmid. The human interferon alpha A (IFN alpha A) gene expression-secretion cassette was inserted into pHC11, and the yeast transformant was cultured in complex medium. The data showed that the expressed product was 36.8% of the total protein amount in the culture supernatant and the IFN alpha A biological activity was 2.6 x 10(10) units per liter, demonstrating that high-level expression and secretion of IFN alpha A were achieved in yeast by using the stable vector pHC11.