期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 289, 期 9, 页码 6236-6247出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M113.499608
关键词
Hsp90; Protein Assembly; RNA Polymerase II; Small Nucleolar RNA (snoRNA); TOR Complex (TORC); Hsp70; R2TP Complex; RPAP3; Spaghetti Gene
资金
- La Ligue Nationale Contre le Cancer
- ANR
- Czech Grant Foundation Grant [P302/11/1640]
- Charles University Center [UNCE 204022]
- First Faculty of Medicine [Prvouk/ILF/1]
- Agence National de la Recherche Grant [ANR-11-BSV8-015-03]
- LABEX DYNAMO Grant [ANR-11-LABX-0011]
- Fondation Agence National de la Recherche pour la Recherche sur le Cancer Grant [SFI20101201793]
Background: Mammalian RNA polymerase II-associated protein 3 (RPAP3) recruits heat shock protein 90 (Hsp90) to assemble cellular machineries such as RNA polymerases. Results:Spaghetti encodes the Drosophila homolog of RPAP3. Spaghetti is essential for development. Spag protein binds and stimulates Hsp90 and Hsp70. Conclusion: RPAP3 function is conserved among metazoans. Significance: Our data suggest that Hsp70 assists RPAP3 in complex assembly. 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.
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