title: Pleiotropic corepressors Sin3 and Ssn6 interact with repressor Opi1 and negatively regulate transcription of genes required for phospholipid biosynthesis in the yeast Saccharomyces cerevisiae.
abstract: Repressor protein Opi1 is required to negatively regulate yeast structural genes of phospholipid biosynthesis in the presence of precursor molecules inositol and choline (IC). Opi1 interacts with the paired amphipathic helix 1 (PAH1) of pleiotropic corepressor Sin3, leading to recruitment of histone deacetylases (HDACs). Mutational analysis of the Opi1-Sin3 interaction domain (OSID) revealed that hydrophobic OSID residues L56, V59 and V67 of Opi1 are indispensable for gene repression. Our results also suggested that repression is not executed entirely via Sin3. Indeed, we could show that OSID contacts a second pleiotropic corepressor, Ssn6 (=Cyc8), which together with Tup1 is also able to recruit HDACs. Interestingly, mutations sin3 and ssn6 turned out as synthetically lethal. Our analysis further revealed that OSID not only binds to PAH1 but also interacts with tetratricopeptide repeats (TPR) of Ssn6. This interaction could no longer be observed with Opi1 OSID variants. To trigger gene repression, Opi1 must also interact with activator Ino2, using its activator interaction domain (AID). AID contains a hydrophobic structural motif reminiscent of a leucine zipper. Our mutational analysis of selected positions indeed confirmed that residues L333, L340, V343, V350, L354 and V361 are necessary for repression of Opi1 target genes.
authors.affiliation: Institut für Genetik und Funktionelle Genomforschung, Jahnstrasse 15a, 17487 Greifswald, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Jäschke
authors.forename: Juliane
authors.initials: J
authors.lastname: Schwarz
authors.forename: Diana
authors.initials: D
authors.lastname: Clausnitzer
authors.forename: Carina
authors.initials: C
authors.lastname: Müller
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Schüller
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D015966:Gene Expression Regulation, Fungal; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010743:Phospholipids / Q000096:biosynthesis*; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D006655:Histone Deacetylases; D010743:Phospholipids; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C065455:CYC8 protein, S cerevisiae; C095723:INO2 protein, S cerevisiae; C096105:OPI1 protein, S cerevisiae; C071731:SIN3 protein, S cerevisiae