earticle

영어

Effects of continuous expression of an unfolded protein response (UPR) gene were investigated in recombinant Saccharomyces cerevisiae strains harbouring 16 copies of the gene for human kringle protein, LK8. In S. cerevisiae, Hac1p plays a crucial role as a transcription activator and Ire1p as an endonuclease acting on the HAC1 transcript to remove an intron and induce the UPR. The disruption of the two genes was detrimental to LK8 expression, and interestingly, the hac1Δ strain was not able to utilize galactose as a carbon source and concomitantly delayed cell growth compared with the wild type and the ire1Δ strains. In a complementation test, the growth defect was partially recovered by the coexpression of the HAC1 gene controlled by the GAL1 promoter. A continuous activation of UPR was mediated by the GAL1 promoter driven coexpression of the HAC1 gene and enhanced the intracellular and secreted levels of LK8 by 4- and 1.6-fold, respectively. The UPR was essentially required for the heterologous production of LK8. Furthermore, Hac1p is the factor, which enables LK8 protein production as well as cell growth in recombinant S. cerevisiae strains. Continuous expression of the HAC1 gene elevated LK8 production level. This result indicates that the continuous activation of UPR might be a good option for overproduction of heterologous proteins in S. cerevisiae.