Efficient Mammalian Protein Synthesis Requires an Intact F-Actin System*
- From the Department of Biochemistry, University of Connecticut Health Center, Farmington, Connecticut 06030 and the§Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, Florida 33101-6129
Abstract
The mammalian protein synthesizing system is highly organized in vivo, and its substrate, tRNA, is channeled throughout the translation process. However, the cellular components responsible for this organization are not known. To examine this question a series of studies was carried out using intact and permeabilized Chinese hamster ovary cells. We show that cold shock dramatically reduces the protein synthetic capacity of these cells by as much as 95%. The loss of activity can be reversed by a short recovery period under conditions that allow energy metabolism to occur; transcription and translation during the recovery period are not needed. While individual components of the translation apparatus are not inactivated by the cold shock, the supramolecular organization of the system appears to be altered and F-actin levels are found to decrease. Resumption of protein synthesis during the recovery period coincides closely with the restoration of F-actin to normal levels. Moreover, disruption of actin filaments, but not microtubules, also leads to a major reduction in translation. These data support the conclusion that the cellular microfilament network plays an important role in the structure and function of the translation system and that perturbations of this network can have profound effects on protein synthesis.
Footnotes
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↵* This work was supported by Grant GM16317 from the National Institutes of Health.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Present address: Dept. of Biochemistry, Kaunas Medical Academy, Kaunas, Lithuania.
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↵¶ To whom reprint requests should be addressed. Tel.: 305-243-3150; Fax: 305-243-3955; E-mail:mdeutsch{at}mednet.med.miami.edu.
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↵1 The abbreviations used are: CHO, Chinese hamster ovary; PBS, phosphate-buffered saline; EF-1a, elongation factor 1a; TRITC, tetramethylrhodaminyl phalloidin.
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↵2 R. Stapulionis and M. P. Deutscher, unpublished observation.
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- Received May 7, 1997.
- Revision received July 24, 1997.
