title: Genetic evidence links the ASTRA protein chaperone component Tti2 to the SAGA transcription factor Tra1.
abstract: Tra1 is a 3744-residue component of the Saccharomyces cerevisiae SAGA, NuA4, and ASTRA complexes. Tra1 contains essential C-terminal PI3K and FATC domains, but unlike other PIKK (phosphoinositide three-kinase-related kinase) family members, lacks kinase activity. To analyze functions of the FATC domain, we selected for suppressors of tra1-F3744A, an allele that results in slow growth under numerous conditions of stress. Two alleles of TTI2, tti2-F328S and tti2-I336F, acted in a partially dominant fashion to suppress the growth-related phenotypes associated with tra1-F3744A as well as its resulting defects in transcription. tti2-F328S suppressed an additional FATC domain mutation (tra1-L3733A), but not a mutation in the PI3K domain or deletions of SAGA or NuA4 components. We find eGFP-tagged Tti2 distributed throughout the cell. Tti2 is a component of the ASTRA complex, and in mammalian cells associates with molecular chaperones in complex with Tti1 and Tel2. Consistent with this finding, Tra1 levels are reduced in a strain with a temperature-sensitive allele of tel2. Further agreeing with a possible role for Tti2 in the folding or stabilization of Tra1, tra1-F3744A was mislocalized to the cytoplasm, particularly under conditions of stress. Since an intragenic mutation of tra1-R3590I also suppressed F3744A, we propose that Tti2 is required for the folding/stability of the C-terminal FATC and PI3K domains of Tra1 into their functionally active form.
authors.affiliation: Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5C1.
authors.forename: Julie
authors.initials: J
authors.lastname: Genereaux
authors.forename: Stephanie
authors.initials: S
authors.lastname: Kvas
authors.forename: Dominik
authors.initials: D
authors.lastname: Dobransky
authors.forename: Jim
authors.initials: J
authors.lastname: Karagiannis
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Gloor
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Brandl
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D000431:Ethanol / Q000494:pharmacology; D051548:Histone Acetyltransferases / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D013696:Temperature; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D018832:Molecular Chaperones; C507785:SAGA complex, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C491364:TRA1 protein, S cerevisiae; D015534:Trans-Activators; C576144:Tti2 protein, S cerevisiae; D000431:Ethanol; D051548:Histone Acetyltransferases