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