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Cloning and characterization of cDNA encoding rat hemin-sensitive initiation factor-2 alpha (eIF-2 alpha) kinase.
H Mellor1, K M Flowers, S R Kimball
1Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey 17033.
The Journal of Biological Chemistry
|April 8, 1994
Summary
Researchers identified a hemin-sensitive eukaryotic initiation factor-2 alpha (eIF-2 alpha) kinase in rat brain, showing homology to rabbit reticulocyte HCR. This kinase is expressed in various non-erythroid tissues, suggesting broader roles beyond red blood cells.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Reticulocytes possess a hemin-regulated eukaryotic initiation factor-2 alpha (eIF-2 alpha) kinase, known as heme-controlled repressor (HCR).
- HCR significantly inhibits protein synthesis initiation and is crucial for translational control in reticulocytes.
- Prior research suggested HCR might be exclusive to erythroid cells.
Purpose of the Study:
- To clone and characterize the cDNA encoding an eIF-2 alpha kinase from rat brain.
- To investigate the homology between the brain kinase and rabbit reticulocyte HCR.
- To determine the expression pattern of the rat brain kinase in various tissues.
Main Methods:
- Cloning and characterization of rat brain cDNA encoding an eIF-2 alpha kinase.
- Expression of the rat brain cDNA in Escherichia coli to produce recombinant enzyme.
- Analysis of amino acid sequence homology between the brain kinase and rabbit reticulocyte HCR.
- Northern blot analysis to assess mRNA expression in different rat tissues.
Main Results:
- The predicted amino acid sequence of the rat brain kinase exhibits 82% homology to rabbit reticulocyte HCR.
- The recombinant rat brain enzyme functions as a hemin-sensitive eIF-2 alpha kinase.
- mRNA for this kinase is detectable in a broad spectrum of non-erythroid rat tissues, albeit at lower levels than in reticulocytes.
Conclusions:
- The rat brain kinase is a functional homolog of rabbit reticulocyte HCR.
- The widespread expression of HCR mRNA in non-erythroid tissues suggests potential uncharacterized functions beyond translational control in red blood cells.
- These findings challenge the notion of HCR as an erythroid-specific enzyme.