title: Yar1 protects the ribosomal protein Rps3 from aggregation.
abstract: 2000 ribosomes have to be synthesized in yeast every minute. Therefore the fast production of ribosomal proteins, their efficient delivery to the nucleus and correct incorporation into ribosomal subunits are prerequisites for optimal growth rates. Here, we report that the ankyrin repeat protein Yar1 directly interacts with the small ribosomal subunit protein Rps3 and accompanies newly synthesized Rps3 from the cytoplasm into the nucleus where Rps3 is assembled into pre-ribosomal subunits. A yar1 deletion strain displays a similar phenotype as an rps3 mutant strain, showing an accumulation of 20S pre-rRNA and a 40S export defect. The combination of an rps3 mutation with a yar1 deletion leads to an enhancement of these phenotypes, while increased expression of RPS3 suppresses the defects of a yar1 deletion strain. We further show that Yar1 protects Rps3 from aggregation in vitro and increases its solubility in vivo. Our data suggest that Yar1 is a specific chaperone for Rps3, which serves to keep Rps3 soluble until its incorporation into the pre-ribosome.
authors.affiliation: Institut für Molekulare Biowissenschaften, Universität Graz, Humboldtstrasse 50, A-8010 Graz, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Koch
authors.forename: Valentin
authors.initials: V
authors.lastname: Mitterer
authors.forename: Johannes
authors.initials: J
authors.lastname: Niederhauser
authors.forename: Tamsyn
authors.initials: T
authors.lastname: Stanborough
authors.forename: Guillaume
authors.initials: G
authors.lastname: Murat
authors.forename: Gerald
authors.initials: G
authors.lastname: Rechberger
authors.forename: Helmut
authors.initials: H
authors.lastname: Bergler
authors.forename: Dieter
authors.initials: D
authors.lastname: Kressler
authors.forename: Brigitte
authors.initials: B
authors.lastname: Pertschy
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism; D018833:Chaperonins / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D009154:Mutation; D011994:Recombinant Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*; D012568:Schizosaccharomyces / Q000378:metabolism; D013395:Sucrose / Q000737:chemistry
chemical_list: C501334:RPS3 protein, S cerevisiae; D011994:Recombinant Proteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; C099981:YAR1 protein, S cerevisiae; D049452:Green Fluorescent Proteins; D013395:Sucrose; D018833:Chaperonins