EFFICIENT SYNTHESIS OF SECRETED MURINE INTERLEUKIN-2 BY SACCHAROMYCES-CEREVISIAE - INFLUENCE OF 3'-UNTRANSLATED REGIONS AND CODON USAGE

Several expression vectors were compared which directed the synthesis of secreted murine interleukin-2 (mIL2) in the culture medium of Saccharomyces cerevisiae. We used the prepro-sequence of the alpha-1 mating-factor precursor as a secretion signal in S. cerevisiae in combination with different promoters. The yield of mature mIL2 was significantly improved by deleting the major part of the 3'-untranslated region (UTR). In Northern-blotting experiments we showed that a destabilizing sequence present in the 3' UTR might be responsible for rapid degradation of the mIL2 mRNA. The highest expression (about 10-mu-g/ml) was obtained under control of the GAL1 promoter in an S. cerevisiae strain where the regulatory GAL4 gene was overexpressed. No difference in expression level was observed in a construct wherein twelve consecutive codons were replaced by optimal codons for S. cerevisiae.