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Originally published as MBC in Press, 10.1091/mbc.E07-08-0774 on November 28, 2007

Vol. 19, Issue 2, 546-552, February 2008

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The 90-kDa Heat Shock Protein Stabilizes the Polysomal Ribonuclease 1 mRNA Endonuclease to Degradation by the 26S Proteasome

Yong Peng*, Xiaoqiang Liu, and Daniel R. Schoenberg

Department of Molecular and Cellular Biochemistry, RNA Group and the Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210

Submitted August 16, 2007; Revised November 1, 2007; Accepted November 15, 2007
Monitoring Editor: A. Gregory Matera

The polysomal ribonuclease 1 (PMR1) mRNA endonuclease forms a selective complex with its translating substrate mRNAs where it is activated to initiate mRNA decay. Previous work showed tyrosine phosphorylation is required for PMR1 targeting to this polysome-bound complex, and it identified c-Src as the responsible kinase. c-Src phosphorylation occurs in a distinct complex, and the current study shows that 90-kDa heat shock protein (Hsp90) is also recovered with PMR1 and c-Src. Hsp90 binding to PMR1 is inhibited by geldanamycin, and geldanamycin stabilizes substrate mRNA to PMR1-mediated decay. PMR1 is inherently unstable and geldanamycin causes PMR1 to rapidly disappear in a process that is catalyzed by the 26S proteasome. We present a model where Hsp90 interacts transiently to stabilize PMR1 in a manner similar to its interaction with c-Src, thus facilitating the tyrosine phosphorylation and targeting of PMR1 to polysomes.

This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E07-08-0774) on November 28, 2007.

* Present address: Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY 10032.

Address correspondence to: Daniel R. Schoenberg (schoenberg.3{at}osu.edu)






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