The production level of CPY in Saccharomyces cerevisiae KS58-2D/pCY303 was drastically decreased when thiamine was not added to the culture medium. We isolated and characterized the mutants that could produce CPY even though thiamine was absent from the medium. Using complementation screening in the mutants obtained, we isolated a gene that was involved in the thiamine-inducible expression, TIE1, which corresponded to the YDR325w ORF on chromosome IV. The predicted protein sequence of TIE1 did not have significant homology to proteins from public databases. The disruption of the TIE1 gene caused two phenotypes, increase of expression level in thiamine-free medium and ethanol sensitivity. This increase in thiamine-free medium was also observed in the expression under the control of ENO1 or ADH1 promoter in addition to the GAL10 promoter, suggesting that the TIE1 protein is associated with a similar kind of transcriptional mechanism regulated by thiamine.

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