The long-term objectives are the elucidation of the regulation of hemoglobin synthesis and erythropoiesis in normal and abnormal hematologic conditions. The focus of this research is to study the mechanisms of regulation of heme-regulated EIF-2a kinase (HRI) at the molecular structural level. HRI is a potent inhibitor of protein synthesis in immature erythroid cells. Protein synthesis in intact reticulocytes and their lysates is dependent on the availability of heme. In heme-deficiency, protein synthesis is inhibited at the level of initiation due to the activation of HRI. HRI is a heme-regulated protein kinase that phosphorylates the a-subunit of EIF-2 impairs its recycling in translational initiation and results in the cessation of protein synthesis. HRI is mainly expressed in erythroid cells and the physiological role of HRI is to maintain the balanced synthesis of heme and globin chains.
The specific aims of this proposed study are (1) Regulation of HRI by phosphorylation; (2) Molecular mechanisms in the regulation of HRI by heme, the prosthetic group of hemoglobin which is the principal proteins in reticulocytes; ( 3) Determination of HRI structure by X-ray crystallography. The methods to be employed are recombinant DNA techniques, polymerase chain reaction, synthesis of oligodeoxynucleotides, high pressure liquid chromatography, amino acid microsequencing, in vitro transcription and translation, protein kinase assays, gel electrophoresis, deoxynucleotide sequencing, expression of HRI and other proteins using recombinant baculovirus, immunoaffinity column chromatography, immunoprecipitation, Western blot analysis, and X-ray crystallography. HRI is a key regulator of protein synthesis, a process which is essential for the regulation of cell growth, differentiation, antiviral response and hormonal responses. Structure-function analysis of HRI will advance our knowledge not only on the regulation of protein kinases which are vital in the regulation of various cellular processes, but also on the regulation of heme proteins.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK053223-02
Application #
2872246
Study Section
Hematology Subcommittee 2 (HEM)
Program Officer
Badman, David G
Project Start
1998-02-15
Project End
2002-01-31
Budget Start
1999-02-01
Budget End
2000-01-31
Support Year
2
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Type
Organized Research Units
DUNS #
City
Cambridge
State
MA
Country
United States
Zip Code
02139
Chen, Jane-Jane (2007) Regulation of protein synthesis by the heme-regulated eIF2alpha kinase: relevance to anemias. Blood 109:2693-9
Rafie-Kolpin, Maryam; Han, An-Ping; Chen, Jane-Jane (2003) Autophosphorylation of threonine 485 in the activation loop is essential for attaining eIF2alpha kinase activity of HRI. Biochemistry 42:6536-44
Zhan, Ke; Vattem, Krishna M; Bauer, Bettina N et al. (2002) Phosphorylation of eukaryotic initiation factor 2 by heme-regulated inhibitor kinase-related protein kinases in Schizosaccharomyces pombe is important for fesistance to environmental stresses. Mol Cell Biol 22:7134-46
Bauer, B N; Rafie-Kolpin, M; Lu, L et al. (2001) Multiple autophosphorylation is essential for the formation of the active and stable homodimer of heme-regulated eIF2alpha kinase. Biochemistry 40:11543-51
Shao, J; Grammatikakis, N; Scroggins, B T et al. (2001) Hsp90 regulates p50(cdc37) function during the biogenesis of the activeconformation of the heme-regulated eIF2 alpha kinase. J Biol Chem 276:206-14
Rafie-Kolpin, M; Chefalo, P J; Hussain, Z et al. (2000) Two heme-binding domains of heme-regulated eukaryotic initiation factor-2alpha kinase. N terminus and kinase insertion. J Biol Chem 275:5171-8
Uma, S; Matts, R L; Guo, Y et al. (2000) The N-terminal region of the heme-regulated eIF2alpha kinase is an autonomous heme binding domain. Eur J Biochem 267:498-506
Chefalo, P J; Oh, J; Rafie-Kolpin, M et al. (1998) Heme-regulated eIF-2alpha kinase purifies as a hemoprotein. Eur J Biochem 258:820-30