A positive regulatory site and a negative regulatory site control the expression of the Saccharomyces cerevisiae CYC7 gene.

A series of BAL31 deletions were constructed in vitro in the upstream region of the Saccharomyces cerevisiae CYC7 gene, encoding the iso-2-cytochrome c protein. These deletions identified two sites which play a role in governing the expression of this gene. A positive site, the deletion of which led to decreased CYC7 expression, lay ca. 240 base pairs 5' to the translational initiation codon (-240). A negative site, the deletion of which led to greatly increased levels of CYC7 expression, lay at ca. -300 bp. Deletion of both these sites resulted in low wild-type-like expression of the gene. Therefore, these two sites appear to act antagonistically to give the low wild-type levels of CYC7 expression. Within the region defined as containing the positive site, there is a sequence which bears some homology to the upstream activation sites in the regulated gene, CYC1, encoding the iso-1-cytochrome c protein.