Production of a functional mouse interferon γ from recombinant Saccharomyces cerevisiae

The mouse interferon gene (MuIFN-γ) was cloned and then used to transform Saccharomyces cerevisiae. Expressed MuIFN-γ protein (MuIFN-γ) was successfully secreted into culture medium due to the presence of the signal peptide of rice amylase 1A. Two different promoters fused to MuIFN-γ were tested: glyceraldehyde-3-phosphate dehydrogenase (GPD) promoter and a yeast hybrid ADH2-GPD (AG) promoter consisting of alcohol dehydrogenase II (ADH2) and GPD promoter. Using the hybrid promoter, the accumulation of MuIFN-γ transcript was the highest after 24 h cultivation, and then gradually decreased as the cultivation proceeded. However, both cell growth and recombinant MuIFN-γ production reached their peaks after the 4-day cultivation. It was possible to produce 6.5 mg/l of MuIFN-γ without any changes in cell growth. Using GPD promoter, the MuIFN-γ transcript accumulation and the recombinant MuIFN-γ production followed the same pattern as the cell growth. However, compared to that of the hybrid promoter, the production of recombinant MuIFN-γ was 0.2 mg/l. The secreted MuIFN-γ had estimated molecular masses of 21 kDa and 23 kDa, which were larger than that of the encoded size due to glycosylation. The protection assay against the viral infection indicated that the recombinant MuIFN-γ was bioactive.