Tup1Cyc8

Tup1Cyc8 refers to a well-characterized transcriptional corepressor complex found in the yeast Saccharomyces cerevisiae. This complex is composed of two primary proteins: Tup1 and Cyc8. Tup1 is a general corepressor, meaning it can interact with a variety of DNA-binding proteins to inhibit gene expression. Cyc8, also known as SSN6, acts as a scaffold protein and recruits Tup1 to target promoters. The interaction between Tup1 and Cyc8 is essential for the formation of the active corepressor complex.

The Tup1Cyc8 complex functions by recruiting histone deacetylases (HDACs) to the promoter regions of target genes. These HDACs then remove acetyl groups from histone proteins, leading to chromatin condensation. Condensed chromatin is less accessible to the transcriptional machinery, thereby repressing gene expression. This repression is crucial for various cellular processes in yeast, including the regulation of carbon source metabolism, mating-type switching, and the response to environmental stresses.

Key targets of Tup1Cyc8 repression include genes involved in glucose metabolism, which are typically repressed when yeast cells are grown on a non-fermentable carbon source like ethanol. The complex also plays a role in maintaining the repressed state of genes associated with different mating types, ensuring proper cell identity. Genetic studies have shown that mutations in either Tup1 or Cyc8 lead to derepression of these target genes, highlighting their critical role in transcriptional regulation. The Tup1Cyc8 complex is a fundamental component of gene silencing mechanisms in yeast.