Thiamine repression and pyruvate decarboxylase autoregulation independently control the expression of the Saccharomyces cerevisiae PDC5 gene

The Saccharomyces cerevisiae gene PDC5 encodes the minor isoform of pyruvat e decarboxylase (Pdc), In this work we show that expression of PDC5 but not that of PDC1, which encodes the major isoform, is repressed by thiamine, H ence, under thiamine limitation both PDC1 and PDC5 are expressed. PDC5 also becomes strongly expressed in a pdc1 Delta mutant. Two-dimensional gel ele ctrophoresis of whole protein extracts shows that thiamine limitation stimu lates the production of THI gene products and of Pdc5p, Deletion of PDCI on ly stimulates production of Pdc5p, We conclude that the stimulation of PDC5 expression in a pdc1 Delta mutant is not due to a response to thiamine Lim itation. (C) 1999 Federation of European Biochemical Societies.