Organization of the regulatory region of the yeast CYC7 gene: multiple factors are involved in regulation.
Regulation of the CYC7 gene of Saccharomyces cerevisiae, encoding iso-2-cytochrome c, was studied. Expression was induced about 20-fold by heme and derepressed 4- to 8-fold by a shift from glucose medium to one containing a nonfermentable carbon source. Deletion analysis showed that induction by heme depends upon sequences between -250 and -228 (from the coding sequence) and upon the HAP1 activator gene, previously shown to be required for CYC1 expression (L. Guarente et al., Cell 36:503-511, 1984). Thus, HAP1 coordinates expression of CYC7 and CYC1, the two genes encoding isologs of cytochrome c in S. cerevisiae. HAP1-18, a mutant allele of HAP1, which increased CYC7 expression more than 10-fold, also acted through sequences between -250 and -228. In vitro binding studies showed that the HAP1 product binds to these sequences (see also K. Pfeifer, T. Prezant, and L. Guarente, Cell 49:19-28, 1987) and an additional factor binds to distal sequences that lie between -201 and -165. This latter site augmented CYC7 expression in vivo. Derepression of CYC7 expression in a medium containing nonfermentable carbon sources depended upon sequences between -354 and -295. The interplay of these multiple sites and the factors that bind to them are discussed.
Prezant
T
T
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Pfeifer
K
K
Guarente
L
L
D002874:Chromosome Mapping; D003574:Cytochrome c Group / Q000235:genetics*; D045304:Cytochromes c; D005786:Gene Expression Regulation; D005800:Genes, Fungal; D005809:Genes, Regulator; D005947:Glucose / Q000502:physiology; D006418:Heme / Q000502:physiology; D009154:Mutation; D012045:Regulatory Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics
D003574:Cytochrome c Group; D014157:Transcription Factors; C032139:iso-2-cytochrome C; D006418:Heme; D045304:Cytochromes c; D005947:Glucose