This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Uma, S. Articles by Matts, R. L. Search for Related Content PubMed PubMed Citation Articles by Uma, S. Articles by Matts, R. L.

Molecular and Cellular Biology, September 1999, p. 5861-5871, Vol. 19, No. 9
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Dual Role for Hsc70 in the Biogenesis and Regulation of the Heme-Regulated Kinase of the  Subunit of Eukaryotic Translation Initiation Factor 2

Sheri Uma, Vanitha Thulasiraman, and Robert L. Matts^*

Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078-3035

Received 25 February 1999/Returned for modification 26 March 1999/Accepted 29 May 1999

The heme-regulated kinase of the  subunit of eukaryotic initiation factor 2 (HRI) is activated in rabbit reticulocyte lysate (RRL) in response to a number of environmental conditions, including heme deficiency, heat shock, and oxidative stress. Activation of HRI causes an arrest of initiation of protein synthesis. Recently, we have demonstrated that the heat shock cognate protein Hsc70 negatively modulates the activation of HRI in RRL in response to these environmental conditions. Hsc70 is also known to be a critical component of the Hsp90 chaperone machinery in RRL, which plays an obligatory role for HRI to acquire and maintain a conformation that is competent to activate. Using de novo-synthesized HRI in synchronized pulse-chase translations, we have examined the role of Hsc70 in the regulation of HRI biogenesis and activation. Like Hsp90, Hsc70 interacted with nascent HRI and HRI that was matured to a state which was competent to undergo stimulus-induced activation (mature-competent HRI). Interaction of HRI with Hsc70 was required for the transformation of HRI, as the Hsc70 antagonist clofibric acid inhibited the folding of HRI into a mature-competent conformation. Unlike Hsp90, Hsc70 also interacted with transformed HRI. Clofibric acid disrupted the interaction of Hsc70 with transformed HRI that had been matured and transformed in the absence of the drug. Disruption of Hsc70 interaction with transformed HRI in heme-deficient RRL resulted in its hyperactivation. Furthermore, activation of HRI in response to heat shock or denatured proteins also resulted in a similar blockage of Hsc70 interaction with transformed HRI. These results indicate that Hsc70 is required for the folding and transformation of HRI into an active kinase but is subsequently required to negatively attenuate the activation of transformed HRI.

---

^* Corresponding author. Mailing address: 246 NRC, Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078-3035. Phone: (405) 744-6200. Fax: (405) 744-7799. E-mail: rlmatts{at}okway.okstate.edu.

Present address: Department of Biological Sciences, Stanford University, Stanford, CA 94305.

---

Molecular and Cellular Biology, September 1999, p. 5861-5871, Vol. 19, No. 9
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

This article has been cited by other articles:

• Lee, H. C., Hon, T., Lan, C., Zhang, L. (2003). Structural Environment Dictates the Biological Significance of Heme-Responsive Motifs and the Role of Hsp90 in the Activation of the Heme Activator Protein Hap1. Mol. Cell. Biol. 23: 5857-5866 [Abstract] [Full Text]  
• Pang, Q., Christianson, T. A., Keeble, W., Koretsky, T., Bagby, G. C. (2002). The Anti-apoptotic Function of Hsp70 in the Interferon-inducible Double-stranded RNA-dependent Protein Kinase-mediated Death Signaling Pathway Requires the Fanconi Anemia Protein, FANCC. J. Biol. Chem. 277: 49638-49643 [Abstract] [Full Text]  
• Zhan, K., Vattem, K. M., Bauer, B. N., Dever, T. E., Chen, J.-J., Wek, R. C. (2002). Phosphorylation of Eukaryotic Initiation Factor 2 by Heme-Regulated Inhibitor Kinase-Related Protein Kinases in Schizosaccharomyces pombe Is Important for Resistance to Environmental Stresses. Mol. Cell. Biol. 22: 7134-7146 [Abstract] [Full Text]  
• Ma, K., Vattem, K. M., Wek, R. C. (2002). Dimerization and Release of Molecular Chaperone Inhibition Facilitate Activation of Eukaryotic Initiation Factor-2 Kinase in Response to Endoplasmic Reticulum Stress. J. Biol. Chem. 277: 18728-18735 [Abstract] [Full Text]  
• Hon, T., Lee, H. C., Hach, A., Johnson, J. L., Craig, E. A., Erdjument-Bromage, H., Tempst, P., Zhang, L. (2001). The Hsp70-Ydj1 Molecular Chaperone Represses the Activity of the Heme Activator Protein Hap1 in the Absence of Heme. Mol. Cell. Biol. 21: 7923-7932 [Abstract] [Full Text]  
• Lu, L., Han, A.-P., Chen, J.-J. (2001). Translation Initiation Control by Heme-Regulated Eukaryotic Initiation Factor 2alpha Kinase in Erythroid Cells under Cytoplasmic Stresses. Mol. Cell. Biol. 21: 7971-7980 [Abstract] [Full Text]  
• Gabai, V. L., Yaglom, J. A., Volloch, V., Meriin, A. B., Force, T., Koutroumanis, M., Massie, B., Mosser, D. D., Sherman, M. Y. (2000). Hsp72-Mediated Suppression of c-Jun N-Terminal Kinase Is Implicated in Development of Tolerance to Caspase-Independent Cell Death. Mol. Cell. Biol. 20: 6826-6836 [Abstract] [Full Text]  
• Shao, J., Grammatikakis, N., Scroggins, B. T., Uma, S., Huang, W., Chen, J.-J., Hartson, S. D., Matts, R. L. (2001). Hsp90 Regulates p50cdc37 Function during the Biogenesis of the Active Conformation of the Heme-regulated eIF2alpha Kinase. J. Biol. Chem. 276: 206-214 [Abstract] [Full Text]  
• Uma, S., Yun, B.-G., Matts, R. L. (2001). The Heme-regulated Eukaryotic Initiation Factor 2alpha Kinase. A POTENTIAL REGULATORY TARGET FOR CONTROL OF PROTEIN SYNTHESIS BY DIFFUSIBLE GASES. J. Biol. Chem. 276: 14875-14883 [Abstract] [Full Text]