title: Drosophila Spag is the homolog of RNA polymerase II-associated protein 3 (RPAP3) and recruits the heat shock proteins 70 and 90 (Hsp70 and Hsp90) during the assembly of cellular machineries.
abstract: The R2TP is a recently identified Hsp90 co-chaperone, composed of four proteins as follows: Pih1D1, RPAP3, and the AAA(+)-ATPases RUVBL1 and RUVBL2. In mammals, the R2TP is involved in the biogenesis of cellular machineries such as RNA polymerases, small nucleolar ribonucleoparticles and phosphatidylinositol 3-kinase-related kinases. Here, we characterize the spaghetti (spag) gene of Drosophila, the homolog of human RPAP3. This gene plays an essential function during Drosophila development. We show that Spag protein binds Drosophila orthologs of R2TP components and Hsp90, like its yeast counterpart. Unexpectedly, Spag also interacts and stimulates the chaperone activity of Hsp70. Using null mutants and flies with inducible RNAi, we show that spaghetti is necessary for the stabilization of snoRNP core proteins and target of rapamycin activity and likely the assembly of RNA polymerase II. This work highlights the strong conservation of both the HSP90/R2TP system and its clients and further shows that Spag, unlike Saccharomyces cerevisiae Tah1, performs essential functions in metazoans. Interaction of Spag with both Hsp70 and Hsp90 suggests a model whereby R2TP would accompany clients from Hsp70 to Hsp90 to facilitate their assembly into macromolecular complexes.
authors.affiliation: From the Equipe Labellisée Ligue Contre le Cancer, Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
authors.forename: Nour El Houda
authors.initials: Nel H
authors.lastname: Benbahouche
authors.forename: Ioannis
authors.initials: I
authors.lastname: Iliopoulos
authors.forename: István
authors.initials: I
authors.lastname: Török
authors.forename: Joachim
authors.initials: J
authors.lastname: Marhold
authors.forename: Julien
authors.initials: J
authors.lastname: Henri
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Kajava
authors.forename: Robert
authors.initials: R
authors.lastname: Farkaš
authors.forename: Tore
authors.initials: T
authors.lastname: Kempf
authors.forename: Martina
authors.initials: M
authors.lastname: Schnölzer
authors.forename: Philippe
authors.initials: P
authors.lastname: Meyer
authors.forename: István
authors.initials: I
authors.lastname: Kiss
authors.forename: Edouard
authors.initials: E
authors.lastname: Bertrand
authors.forename: Bernard M
authors.initials: BM
authors.lastname: Mechler
authors.forename: Bérengère
authors.initials: B
authors.lastname: Pradet-Balade
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D020718:Ribonucleoproteins, Small Nucleolar / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C089272:Hsp83 protein, Drosophila; D018832:Molecular Chaperones; C472351:RPAP3 protein, human; D020718:Ribonucleoproteins, Small Nucleolar; C000601321:SPAG protein, Drosophila; D029701:Saccharomyces cerevisiae Proteins; C571197:Tah1 protein, S cerevisiae; D012319:RNA Polymerase II; D020123:Sirolimus
keywords: Hsp70; Hsp90; Protein Assembly; R2TP Complex; RNA Polymerase II; RPAP3; Small Nucleolar RNA (snoRNA); Spaghetti Gene; TOR Complex (TORC)