|
|
|
|
A more recent version of this article appeared on February 1, 2008
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Submitted on August 16, 2007
Revised on November 1, 2007
Accepted on November 15, 2007
Department of Molecular and Cellular Biochemistry, RNA Group and the Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210
Monitoring Editor: A. Gregory Matera
The 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 identified c-Src as the responsible kinase. c-Src phosphorylation occurs in a distinct complex, and the current study shows that 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.