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Grove DJ, Russell PJ, Kearse MG. To initiate or not to initiate: A critical assessment of eIF2A, eIF2D, and MCT-1·DENR to deliver initiator tRNA to ribosomes. WILEY INTERDISCIPLINARY REVIEWS. RNA 2024; 15:e1833. [PMID: 38433101 PMCID: PMC11260288 DOI: 10.1002/wrna.1833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/15/2024] [Accepted: 01/17/2024] [Indexed: 03/05/2024]
Abstract
Selection of the correct start codon is critical for high-fidelity protein synthesis. In eukaryotes, this is typically governed by a multitude of initiation factors (eIFs), including eIF2·GTP that directly delivers the initiator tRNA (Met-tRNAi Met ) to the P site of the ribosome. However, numerous reports, some dating back to the early 1970s, have described other initiation factors having high affinity for the initiator tRNA and the ability of delivering it to the ribosome, which has provided a foundation for further work demonstrating non-canonical initiation mechanisms using alternative initiation factors. Here we provide a critical analysis of current understanding of eIF2A, eIF2D, and the MCT-1·DENR dimer, the evidence surrounding their ability to initiate translation, their implications in human disease, and lay out important key questions for the field. This article is categorized under: RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes Translation > Mechanisms Translation > Regulation.
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Affiliation(s)
- Daisy J. Grove
- The Ohio State Biochemistry Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Paul J. Russell
- The Ohio State Biochemistry Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
- The Cellular, Molecular, Biochemical Sciences Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Michael G. Kearse
- The Ohio State Biochemistry Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
- The Cellular, Molecular, Biochemical Sciences Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
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Lee JC. Protein synthesis initiation factor 2 from chicken reticulocytes: purification by affinity chromatography and preliminary characterization. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1984; 16:1143-7. [PMID: 6526130 DOI: 10.1016/0020-711x(84)90007-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Affinity chromatography on beta,gamma-methylene guanosine 5'-triphosphate-Sepharose was used to purify protein synthesis initiation factor eIF-2 from chicken reticulocytes. Gel filtration of the purified factor gave a molecular weight of 150,000, whereas electrophoresis of the purified factor on polyacrylamide gel containing sodium dodecyl sulfate revealed three non-identical subunits with apparent molecular weight of 57,000, 41,000 and 33,000. With Met-tRNA and GTP, the factor formed a ternary complex which would bind the 40S ribosomal subunits. Treatment of the factor with N-ethylmaleimide resulted in a loss of activity. Two sulfhydryl groups per eIF-2 molecule were essential for activity.
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3
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Studies on the mechanism of action of a eukaryotic codon-dependent factor specific for initiator Met-tRNAf and ribosomal 40 S subunits. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34608-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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4
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Jakubowicz T, Svoboda AJ, Vaughan MH. Purification and phosphorylation of human initiation factor eIF-2. Biochem Biophys Res Commun 1980; 97:1420-8. [PMID: 7213368 DOI: 10.1016/s0006-291x(80)80024-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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5
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Dwyer B, Wasterlain CG. Regulation of the first step of the initiation of brain protein synthesis by guanosine diphosphate. J Neurochem 1980; 34:1639-47. [PMID: 7381490 DOI: 10.1111/j.1471-4159.1980.tb11255.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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6
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Benne R, Kasperaitis M, Voorma HO, Ceglarz E, Legocki AB. Initiation factor eIF-2 from wheat germ. Purification, functional comparison to eIF-2 from rabbit reticulocytes and phosphorylation of its subunits. EUROPEAN JOURNAL OF BIOCHEMISTRY 1980; 104:109-17. [PMID: 7371632 DOI: 10.1111/j.1432-1033.1980.tb04406.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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7
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Peterson D, Safer B, Merrick W. Role of eukaryotic initiation factor 5 in the formation of 80 S initiation complexes. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(18)36007-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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8
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Peterson D, Merrick W, Safer B. Binding and release of radiolabeled eukaryotic initiation factors 2 and 3 during 80 S initiation complex formation. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30251-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Treadwell BV, Mauser L, Robinson WG. Initiation factors for protein synthesis from wheat germ. Methods Enzymol 1979; 60:181-93. [PMID: 459898 DOI: 10.1016/s0076-6879(79)60015-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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10
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Spremulli L, Walthall B, Lax S, Ravel J. Partial purification of the factors required for the initiation of protein synthesis in wheat germ. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30283-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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11
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Walthall BJ, Spremulli LL, Lax SR, Ravel JM. Isolation and purification of protein synthesis initiation factors from wheat germ. Methods Enzymol 1979; 60:193-204. [PMID: 459899 DOI: 10.1016/s0076-6879(79)60016-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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12
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Malathi VG, Mazumder R. An Artemia salina factor which stimulates the activity of highly purified initiation factor eIF-2 from A. salina and reticulocytes. FEBS Lett 1978; 86:155-9. [PMID: 245317 DOI: 10.1016/0014-5793(78)80552-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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13
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Ochiai-Yanagi S, Malathi VG, Mazumder R. Inhibition of initiation factor eIF-2 activity from artemia salina embryos by transfer RNAs. FEBS Lett 1977; 80:148-52. [PMID: 891960 DOI: 10.1016/0014-5793(77)80427-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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14
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Spremulli LL, Walthall BJ, Lax SR, Ravel JM. Purification and properties of a Met-tRNAf binding factor from wheat germ. Arch Biochem Biophys 1977; 178:565-75. [PMID: 836045 DOI: 10.1016/0003-9861(77)90227-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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15
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Chatterjee B, Dasgupta A, Palmieri S, Gupta NK. Protein synthesis in rabbit reticulocytes. Characteristics of mRNA (AUG codon)-dependent binding of Met-tRNAfMet to 40 S and 80 S ribosomes. J Biol Chem 1976. [DOI: 10.1016/s0021-9258(20)81872-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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16
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Formation of an 80 S methionyl-tRNA initiation complex with soluble factors from wheat germ. J Biol Chem 1976. [DOI: 10.1016/s0021-9258(17)33061-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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17
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Fresno M, Carrasco L, Vazquez D. Initiation of the polypeptide chain by reticulocyte cell-free systems. Survey of different inhibitors of translation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1976; 68:355-64. [PMID: 976261 DOI: 10.1111/j.1432-1033.1976.tb10822.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In order to elucidate the mechanism of action of inhibitors that block the initiation of protein synthesis in mammalian systems, we have studied the following steps: (a) formation of the ternary complex Met-tRNAr-IF-E2-GTP, (b) binding of the initiator Met-tRNAf to the 40-S ribosomal subunit in the presence of initiation factors and dependent or not on the addition of mRNA, (c) formation of the initiation complex with 80-S ribosomes and (d) formation of the first peptide bond. Adrenochrome, aurintricarboxylic acid, polydextran sulphate, pyrochatechol violet and showdomycin block the formation of the ternary complex Met-tRNAf-IF-E2-GTP. Edeine A1, aurintricarboxylic acid and polydextran sulphate block the binding of the mRNA to the 40-S ribosomal subunit. Pactamycin induces the formation of stable smaller initiation complexes which are unable to go through the subsequent steps of initiation. Stimulation of the binding of the initiator Met-tRNAf to the 80-S ribosome in the presence of initiation factors is observed with sparsomycin and antibiotics of the sesquiterpene family (verrucarin A, trichodermin and trichothecin). However, these antibiotics block the reaction of the bound Met-tRNAf with puromycin. Narciclasine has no effect on the binding of the initiator to the ribosome but strongly blocks its reaction with puromycin. We have developed a simple technique to detect the Met-tRNAf-40-S-subunit-poly(A, G, U) initiation complexes by chromatography on Sepharose 6B columns. The requirements for the formation of such complexes measured by this technique and its comparison with the sucrose gradient centrifugation method are described.
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Ochiai-Yanagi S, Mazumder R. Role of GTP in eukaryotic polypeptide-chain initiation. Purification and properties of a factor from Artemia salina embryos which interacts with initiator transfer RNA and guanine nucleotides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1976; 68:395-402. [PMID: 976264 DOI: 10.1111/j.1432-1033.1976.tb10826.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
1. A factor, which makes a ternary complex with GTP and eukaryotic initiator tRNA (Met-tRNAi), has been purified 100-fold from developed cysts of Artemia salina. Some of the properties of the purified factor have been studied. 2. Mg2+ appears to inhibit ternary complex formation. 3. Little or no ternary complex is formed when 5 muM GTP is replaced by an identical concentration of UTP, CTP or ATP. The analog, guanosine 5'-(beta, gamma-imino)triphosphate [GMP-P(NHP)] seems to be a much better substitute for GTP than guanosine 5'-(beta, gamma-methylene)triphosphate [GMP-P(CH2)P]. Since GMP-P(NH)P is as effective as GTP in ternary complex formation, it would appear that GTP plays the role of an allosteric effector in this step of eukaryotic polypeptide chain initiation. 4. GDP inhibits both the rate and extent of ternary complex formation. The inhibition is largely reversed by adding a 5-fold molar excess of GTP over GDP. DGDP is slightly less inhibitory than GDP. UDP and CDP are much less inhibitory than GDP and very little inhibition is obtained with ADP. 5. The preformed ternary complex is rapidly and completely destroyed in the presence of N-ethylmaleimide. The results suggest that free--SH groups of the factor may be essential for maintaining the integrity of the ternary complex.
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20
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Adams SL, Safer B, Anderson WF, Merrick WC. Eukaryotic initiation complex formation. Evidence for two distinct pathways. J Biol Chem 1975. [DOI: 10.1016/s0021-9258(19)40696-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Majumdar A, Reynolds S, Gupta NK. Protein synthesis in rabbit reticulocytes. XIII. Lack of mRNA (poly r (A)) binding activity in highly purified EIF-1. Biochem Biophys Res Commun 1975; 67:689-95. [PMID: 1201048 DOI: 10.1016/0006-291x(75)90867-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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22
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Filipowicz W, Sierra JM, Ochoa S. Polypeptide chain initiation in eukaryotes: initiation factor MP in Artemia salina embryos. Proc Natl Acad Sci U S A 1975; 72:3947-51. [PMID: 1105571 PMCID: PMC433114 DOI: 10.1073/pnas.72.10.3947] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The activity of IF-MP, a polypeptide chain initiation factor that forms a ternary complex with eukaryotic initiator Met-tRNA and GTP and promotes binding of the initiator to 40S ribosomes, is very low in undeveloped Artemia salina embryos but increases over 20-fold following resumption of development upon hydration of the cysts. The factor is present in both the ribosomal salt wash and high-speed-supernatant. Its specific activity is 50 times higher in the wash but its total activity is only about twice as high in the wash as in the supernatant. As is true of IF-MP from other eukaryotic sources, the A. salina factor is specific for eukaryotic Met-tRNAi and sensitive to SH-reagents, and its activity is GTP dependent.
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