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Molecular chaperone Hsp90 stabilizes Pih1/Nop17 to maintain R2TP complex activity that regulates snoRNA accumulation.

Zhao R, Kakihara Y, Gribun A, Huen J, Yang G, Khanna M, Costanzo M, Brost RL, Boone C, Hughes TR, Yip CM, Houry WA - J. Cell Biol. (2008)

Bottom Line: Tah1 is a small protein containing tetratricopeptide repeats, whereas Pih1 is found to be an unstable protein.As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions.Hsp90 and R2TP proteins are also involved in the proper accumulation of box H/ACA small nucleolar RNAs.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.

ABSTRACT
Hsp90 is a highly conserved molecular chaperone that is involved in modulating a multitude of cellular processes. In this study, we identify a function for the chaperone in RNA processing and maintenance. This functionality of Hsp90 involves two recently identified interactors of the chaperone: Tah1 and Pih1/Nop17. Tah1 is a small protein containing tetratricopeptide repeats, whereas Pih1 is found to be an unstable protein. Tah1 and Pih1 bind to the essential helicases Rvb1 and Rvb2 to form the R2TP complex, which we demonstrate is required for the correct accumulation of box C/D small nucleolar ribonucleoproteins. Together with the Tah1 cofactor, Hsp90 functions to stabilize Pih1. As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions. Hsp90 and R2TP proteins are also involved in the proper accumulation of box H/ACA small nucleolar RNAs.

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SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (A) Venn diagram showing the overlap in the hits obtained from the SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (B) Common genetic interactors of PIH1, RVB1, and RVB2 are listed. Hits that were verified by random spore analysis are indicated by asterisks. Note that PIH1:RVB2, for example, means the hits that overlap between PIH1 and RVB2 only and not with RVB1.
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fig5: SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (A) Venn diagram showing the overlap in the hits obtained from the SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (B) Common genetic interactors of PIH1, RVB1, and RVB2 are listed. Hits that were verified by random spore analysis are indicated by asterisks. Note that PIH1:RVB2, for example, means the hits that overlap between PIH1 and RVB2 only and not with RVB1.

Mentions: Synthetic genetic analysis (SGA) screens (Tong et al., 2004) were performed to determine common genetic interactors of RVB1, RVB2, TAH1, and PIH1 (Fig. 5 A) in an effort to elucidate the cellular function of the R2TP complex.tah1Δ and pih1Δ cells were used for this analysis. Rvb1 and Rvb2 are essential for cell viability and cannot be knocked out; thus, hypomorphic DAmP (decreased abundance by mRNA perturbation) alleles of RVB1 and RVB2 (referred to as rvb1-DAmP and rvb2-DAmP, respectively) were constructed (Schuldiner et al., 2005). In these strains, the steady-state levels of Rvb1 and Rvb2 proteins are reduced to ∼30–50% of WT levels by insertion of the nourseothricin (NAT) resistance gene at the 3′ untranslated region of the respective genes (Fig. S5 A, available at http://www.jcb.org/cgi/content/full/jcb.200709061/DC1; and Table I).


Molecular chaperone Hsp90 stabilizes Pih1/Nop17 to maintain R2TP complex activity that regulates snoRNA accumulation.

Zhao R, Kakihara Y, Gribun A, Huen J, Yang G, Khanna M, Costanzo M, Brost RL, Boone C, Hughes TR, Yip CM, Houry WA - J. Cell Biol. (2008)

SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (A) Venn diagram showing the overlap in the hits obtained from the SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (B) Common genetic interactors of PIH1, RVB1, and RVB2 are listed. Hits that were verified by random spore analysis are indicated by asterisks. Note that PIH1:RVB2, for example, means the hits that overlap between PIH1 and RVB2 only and not with RVB1.
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Related In: Results  -  Collection

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fig5: SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (A) Venn diagram showing the overlap in the hits obtained from the SGA analysis of pih1Δ, rvb1-DAmP, and rvb2-DAmP strains. (B) Common genetic interactors of PIH1, RVB1, and RVB2 are listed. Hits that were verified by random spore analysis are indicated by asterisks. Note that PIH1:RVB2, for example, means the hits that overlap between PIH1 and RVB2 only and not with RVB1.
Mentions: Synthetic genetic analysis (SGA) screens (Tong et al., 2004) were performed to determine common genetic interactors of RVB1, RVB2, TAH1, and PIH1 (Fig. 5 A) in an effort to elucidate the cellular function of the R2TP complex.tah1Δ and pih1Δ cells were used for this analysis. Rvb1 and Rvb2 are essential for cell viability and cannot be knocked out; thus, hypomorphic DAmP (decreased abundance by mRNA perturbation) alleles of RVB1 and RVB2 (referred to as rvb1-DAmP and rvb2-DAmP, respectively) were constructed (Schuldiner et al., 2005). In these strains, the steady-state levels of Rvb1 and Rvb2 proteins are reduced to ∼30–50% of WT levels by insertion of the nourseothricin (NAT) resistance gene at the 3′ untranslated region of the respective genes (Fig. S5 A, available at http://www.jcb.org/cgi/content/full/jcb.200709061/DC1; and Table I).

Bottom Line: Tah1 is a small protein containing tetratricopeptide repeats, whereas Pih1 is found to be an unstable protein.As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions.Hsp90 and R2TP proteins are also involved in the proper accumulation of box H/ACA small nucleolar RNAs.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.

ABSTRACT
Hsp90 is a highly conserved molecular chaperone that is involved in modulating a multitude of cellular processes. In this study, we identify a function for the chaperone in RNA processing and maintenance. This functionality of Hsp90 involves two recently identified interactors of the chaperone: Tah1 and Pih1/Nop17. Tah1 is a small protein containing tetratricopeptide repeats, whereas Pih1 is found to be an unstable protein. Tah1 and Pih1 bind to the essential helicases Rvb1 and Rvb2 to form the R2TP complex, which we demonstrate is required for the correct accumulation of box C/D small nucleolar ribonucleoproteins. Together with the Tah1 cofactor, Hsp90 functions to stabilize Pih1. As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions. Hsp90 and R2TP proteins are also involved in the proper accumulation of box H/ACA small nucleolar RNAs.

Show MeSH