title: Rbs1, a new protein implicated in RNA polymerase III biogenesis in yeast Saccharomyces cerevisiae.
abstract: Little is known about the RNA polymerase III (Pol III) complex assembly and its transport to the nucleus. We demonstrate that a missense cold-sensitive mutation, rpc128-1007, in the sequence encoding the C-terminal part of the second largest Pol III subunit, C128, affects the assembly and stability of the enzyme. The cellular levels and nuclear concentration of selected Pol III subunits were decreased in rpc128-1007 cells, and the association between Pol III subunits as evaluated by coimmunoprecipitation was also reduced. To identify the proteins involved in Pol III assembly, we performed a genetic screen for suppressors of the rpc128-1007 mutation and selected the Rbs1 gene, whose overexpression enhanced de novo tRNA transcription in rpc128-1007 cells, which correlated with increased stability, nuclear concentration, and interaction of Pol III subunits. The rpc128-1007 rbs1Δ double mutant shows a synthetic growth defect, indicating that rpc128-1007 and rbs1Δ function in parallel ways to negatively regulate Pol III assembly. Rbs1 physically interacts with a subset of Pol III subunits, AC19, AC40, and ABC27/Rpb5. Additionally, Rbs1 interacts with the Crm1 exportin and shuttles between the cytoplasm and nucleus. We postulate that Rbs1 binds to the Pol III complex or subcomplex and facilitates its translocation to the nucleus.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Cieśla
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Makała
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Płonka
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Rafał
authors.initials: R
authors.lastname: Bazan
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
authors.forename: Kamil
authors.initials: K
authors.lastname: Gewartowski
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Dziembowski
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland magda@ibb.waw.pl.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Boguta
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D060066:Protein Interaction Maps; D021122:Protein Subunits / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D012320:RNA Polymerase III / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D021122:Protein Subunits; C000597856:Rbs1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012320:RNA Polymerase III