Published online February 11, 2008
doi:10.1083/jcb.200709061
The Journal of Cell Biology, Vol. 180, No. 3, 563-578
The Rockefeller University Press, 0021-9525 $30.00
© 2008 Zhao et al.
Molecular chaperone Hsp90 stabilizes Pih1/Nop17 to maintain R2TP complex activity that regulates snoRNA accumulation
Rongmin Zhao1,
Yoshito Kakihara1,
Anna Gribun1,
Jennifer Huen1,
Guocheng Yang1,2,5,
May Khanna3,4,5,
Michael Costanzo3,4,5,
Renée L. Brost3,4,5,
Charles Boone3,4,5,
Timothy R. Hughes3,4,5,
Christopher M. Yip1,2,5, and
Walid A. Houry1
1 Department of Biochemistry, 2 Institute of Biomaterials and Biomedical Engineering, 3 Banting and Best Department of Medical Research, 4 Department of Molecular Genetics and Microbiology, and 5 Terrence Donnelly Center for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario M5S 1A8, Canada
Correspondence to Walid A. Houry: walid.houry{at}utoronto.ca
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.
R. Zhao, Y. Kakihara, and A. Gribun contributed equally to this paper.
Abbreviations used in this paper: 2H, two hybrid; AFM, atomic force microscopy; rRNA, ribosomal RNA; SE, size exclusion; SGA, synthetic genetic analysis; snRNA, small nuclear RNA; snoRNA, small nucleolar RNA; snoRNP, small nucleolar RNP; TEV, tobacco etch virus; TPR, tetratricopeptide repeat; WT, wild type.

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