PDC2, a yeast gene essential for synthesis of pyruvate decarboxylase, encodes a novel transcription factor

Abstract

A positive regulatory gene PDC2 required for expression of the enzyme pyruvate decarboxylase (PDC) in the yeast Saccharomyces cerevisiae has been identified and cloned. The pdc2 mutant lacks pyruvate decarboxylase activity and is unable to grow on a medium containing glucose. PDC2 disruptants are viable on ethanol. The PDC2 gene product is essential for transcription of PDC1 and PDC5, the structural genes of pyruvate decarboxylase. The PDC2 gene codes for a low-abundance mRNA of approximately 2.8 kb. Transformation of a wild-type strain with multiple copies of the promoter ofPDC1 leads to decreased pyruvate decarboxylase activity, presumably owing to titration of trans-acting factors. Normal activity is restored by multiple copies of PDC2, implicating involvement ofPDC2 in transcription of PDC1. The deduced PDC2 protein (Pdc2p) sequence contains 925 amino acids, and is rich in asparagine and serine. We fused the DNA sequence encoding the N-terminal domain of Gal4p to the sequence encoding the C-terminal of Pdc2p; the hybrid protein (Gal4-Pdc2p) was able to activate transcription of the GAL1-lucZ fusion gene. The active domain consists of an unusual structure with a strikingly high asparagine content. We propose that this asparagine-rich domain represents a novel structural motif for transcriptional activation. PDC2 maps on chromosome IV betweencdc34 andarol; PDC1 is on the left arm of chromosome XII, linked topprl.