The Tup1-Ssn6 corepressor complex regulates the expression of several sets of genes, including genes that specify mating type in the yeast Saccharomyces cerevisiae. Repression of mating-type genes occurs when Tup1-Ssn6 is brought to the DNA by the Matα2 DNA-binding protein and assembled upstream of a- and haploid-specific genes. We have determined the 2.3 Å X-ray crystal structure of the C-terminal domain of Tup1 (accesion No. 1ERJ), a 43 kDa fragment that contains seven copies of the WD40 sequence motif and binds to the Matα2 protein. Moreover, this portion of the protein can partially substitute for full-length Tup1 in bringing about transcriptional repression. The structure reveals a seven-bladed β propeller with an N-terminal subdomain that is anchored to the side of the propeller and extends the β sheet of one of the blades. Point mutations in Tup1 that specifically affect the Tup1-Matα2 interaction cluster on one surface of the propeller. We identified regions of Tup1 that are conserved among the fungal Tup1 homologs and may be important in protein-protein interactions with additional components of the Tup1-mediated repression pathways.
- Transcriptional regulation
- WD40 repeat
- X-ray crystal structure
ASJC Scopus subject areas
- Molecular Biology
- Biochemistry, Genetics and Molecular Biology(all)
- Immunology and Microbiology(all)