The yeast CPC2/ASC1 gene is regulated by the transcription factors Fhl1p and Ifh1p

CPC2/ASC1 is one of the most abundantly transcribed genes in Saccharomyces cerevisiae. It encodes a ribosome-associated G beta-like WD protein, which is highly conserved from yeast to man. Here, we show that CPC2 transcription depends on the carbon source and is induced during utilization of the sugar glucose. CPC2 promoter deletion and insertion analyses identified two upstream activation sequence elements for CPC2, which are required for basal expression and regulation. One of these upstream activation sequence elements has an ATGTACGGATGT motif, which has previously been described as a putative binding site for the forkhead-like transcription factor Fhl1p. Deletion of FHL1 reduces CPC2 transcription significantly in presence of glucose, but has no effect when the non-fermentable carbon source ethanol is provided. Increased amounts of the Fhl1p co-regulator Ifh1p induce CPC2 transcription even when ethanol is utilized. These data suggest that the interaction between Fhl1p and Ifh1p is critical for the regulation of CPC2 transcription during utilization of different carbon sources.