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Romaniuk SI, Kolybo DV, Komisarenko SV. Recombinant diphtheria toxin derivatives: Perspectives of application. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2012; 38:639-52. [DOI: 10.1134/s106816201206012x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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2
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Kaul G, Pattan G, Rafeequi T. Eukaryotic elongation factor-2 (eEF2): its regulation and peptide chain elongation. Cell Biochem Funct 2011; 29:227-34. [PMID: 21394738 DOI: 10.1002/cbf.1740] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 01/17/2011] [Accepted: 01/31/2011] [Indexed: 12/19/2022]
Abstract
Regulation at the level of translation in eukaryotes is feasible because of the longer lifetime of eukaryotic mRNAs in the cell. The elongation stage of mRNA translation requires a substantial amount of energy and also eukaryotic elongation factors (eEFs). The important component of eEFs, i.e. eEF2 promotes the GTP-dependent translocation of the nascent protein chain from the A-site to the P-site of the ribosome. Mostly the eEF2 is regulated by phosphorylation and dephosphorylation by a specific kinase known as eEF2 kinase, which itself is up-regulated by various mechanisms in the eukaryotic cell. The activity of this kinase is dependent on calcium ions and calmodulin. Recently it has been shown that the activity of eEF2 kinase is regulated by MAP kinase signalling and mTOR signalling pathway. There are also various stimuli that control the peptide chain elongation in eukaryotic cell; some stimuli inhibit and some activate eEF2. These reports provide the mechanisms by which cells likely serve to slow down protein synthesis and conserve energy under nutrient deprived conditions via regulation of eEF2. The regulation via eEF2 has also been seen in mammary tissue of lactating cows, suggesting that eEF2 may be a limiting factor in milk protein synthesis. Regulation at this level provides the molecular understanding about the control of protein translocation reactions in eukaryotes, which is critical for numerous biological phenomenons. Further the elongation factors could be potential targets for regulation of protein synthesis like milk protein synthesis and hence probably its foreseeable application to synthetic biology.
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Affiliation(s)
- Gautam Kaul
- N.T Lab-I, National Dairy Research Institute, Karnal, Haryana, India.
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3
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Ivankovic M, Rubelj I, Matulic M, Reich E, Brdar B. Site-specific mutagenesis of the histidine precursor of diphthamide in the human elongation factor-2 gene confers resistance to diphtheria toxin. Mutat Res 2006; 609:34-42. [PMID: 16901746 DOI: 10.1016/j.mrgentox.2006.06.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Revised: 05/23/2006] [Accepted: 06/08/2006] [Indexed: 11/20/2022]
Abstract
Protein synthesis elongation factor 2 (EF-2) from eukaryotes contains a conserved post-translationally modified histidine residue known as diphthamide. Diphthamide is a unique site of ADP-ribosylation by diphtheria toxin (DT), which is responsible for cell killing. In this report, we describe the construction of DT-resistant HeLa cell lines by engineering the toxin-resistant form of its specific substrate, protein elongation factor-2. Using site-specific mutagenesis of the histidine precursor of diphthamide, the histidine residue of codon 715 in human EF-2 cDNA was substituted with one of four amino acid residue codons: leucine, methionine, asparagine or glutamine. Mutant EF-2s were subcloned into a pCMVexSVneo expression vector, transfected into HeLa cells, and DT-resistant cell clones were isolated. The protective effect of mutant EF-2s against cell killing by DT, after exposing all four mutant strains derived from HeLa cells to different concentrations of the toxin (5-20 ng/mL) was demonstrated by: (1) the normal morphological appearance of the cells; (2) their unaffected or slightly slower growth rates; (3) their undisturbed electrophoretic DNA profiles whose integrity was virtually preserved. Mutant cell strains showed also considerable levels of resistance to very high concentrations of DT, in that they maintained slower but consistent rates of cell growth. It was hence concluded that despite its strict conservation and unique modification, the diphthamide histidine appears not to be essential to the function of human EF-2 in protein synthesis. In addition, DT-resistant HeLa cell clones should prove valuable hosts for various DT gene-containing vectors that express the toxin intracellularly.
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Affiliation(s)
- Milena Ivankovic
- Department of Molecular Biology, Ruder Bosković Institute, Bijenicka 54, 10000 Zagreb, Croatia
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4
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Abstract
Targeted cancer therapy in general and immunotherapy in particular combines rational drug design with the progress in understanding cancer biology. This approach takes advantage of our recent knowledge of the mechanisms by which normal cells are transformed into cancer cells, thus using the special properties of cancer cells to device novel therapeutic strategies. Recombinant immunotoxins are excellent examples of such processes, combining the knowledge of antigen expression by cancer cells with the enormous developments in recombinant DNA technology and antibody engineering. Recombinant immunotoxins are composed of a very potent protein toxin fused to a targeting moiety such as a recombinant antibody fragment or growth factor. These molecules bind to surface antigens specific for cancer cells and kill the target cells by catalytic inhibition of protein synthesis. Recombinant immunotoxins are developed for solid tumors and hematological malignancies and have been characterized intensively for their biological activity in vitro on cultured tumor cell lines as well as in vivo in animal models of human tumor xenografts. The excellent in vitro and in vivo activities of recombinant immunotoxins have lead to their preclinical development and to the initiation of clinical trail protocols. Recent trail results have demonstrated potent clinical efficacy in patients with malignant diseases that are refractory to traditional modalities of cancer treatment: surgery, radiation therapy, and chemotherapy. The results demonstrate that such strategies can be developed into a separate modality of cancer treatment with the basic rationale of specifically targeting cancer cells on the basis of their unique surface markers. Efforts are now being made to improve the current molecules and to develop new agents with better clinical efficacy. This can be achieved by development of novel targeting moieties with improved specificity that will reduce toxicity to normal tissues. In this review, the design, construction, characterization, and applications of recombinant immunotoxins are described. Results of recent clinical trails are presented, and future directions for development of recombinant immunotoxins as a new modality for cancer treatment are discussed.
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Affiliation(s)
- Y Reiter
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa
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Parrado J, Bougria M, Ayala A, Castaño A, Machado A. Effects of aging on the various steps of protein synthesis: fragmentation of elongation factor 2. Free Radic Biol Med 1999; 26:362-70. [PMID: 9895228 DOI: 10.1016/s0891-5849(98)00202-0] [Citation(s) in RCA: 229] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The possible mechanism responsible for the in vivo protein synthesis decline during aging was studied. In order to determine the effect of aging on the various steps of protein synthesis, we determined the ribosomal state of aggregation and the time of assembly and release of polypeptide chains in the process of protein synthesis in rat liver. The results suggest that elongation is the most sensitive step to aging. A molecular study of the Elongation Factor 2 (EF-2), the main protein involved in the elongation step, shows that this protein has a higher content of carbonyl groups and is less active in old rats. In addition, the molecular mass analysis of EF-2 shows that this protein becomes fragmented in old rats. A similar pattern of fragmentation is found in 3-month-old rats suffering oxidative stress, in that the decline in protein synthesis is similar to that found in old rats. These data suggest that: i) oxidative stress seems to be involved in the modifications of EF-2 observed during aging, and ii) the observed modifications (oxidation and fragmentation) of EF-2 could account for the decline in protein synthesis in old animals.
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Affiliation(s)
- J Parrado
- Departamento de Bioquimica, Bromatologia y Toxicologia, Facultad de Farmacia, Universidad de Sevilla, Spain
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6
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Martemyanov KA, Yarunin AS, Liljas A, Gudkov AT. An intact conformation at the tip of elongation factor G domain IV is functionally important. FEBS Lett 1998; 434:205-8. [PMID: 9738479 DOI: 10.1016/s0014-5793(98)00982-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Three variants of Thermus thermophilus EF-G with mutations in the loop at the distal end of its domain IV were obtained. The replacement of His-573 by Ala and double mutation H573A/D576A did not influence the functional activity of EF-G. On the other hand, the insertion of six amino acids into the loop between residues Asp-576 and Ser-577 reduced the translocational activity of EF-G markedly, while its GTPase activity was not affected. It is concluded that the native conformation of the loop is important for the factor-promoted translocation in the ribosome. The functional importance of the entire EF-G domain IV is discussed.
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Affiliation(s)
- K A Martemyanov
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region
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7
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Rodnina MV, Savelsbergh A, Katunin VI, Wintermeyer W. Hydrolysis of GTP by elongation factor G drives tRNA movement on the ribosome. Nature 1997; 385:37-41. [PMID: 8985244 DOI: 10.1038/385037a0] [Citation(s) in RCA: 368] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Elongation factor G (EF-G) is a GTPase that is involved in the translocation of bacterial ribosomes along messenger RNA during protein biosynthesis. In contrast to current models, EF-G-dependent GTP hydrolysis is shown to precede, and greatly accelerate, the rearrangement of the ribosome that leads to translocation. Domain IV of the EF-G structure is crucial for both rapid translocation and subsequent release of the factor from the ribosome. By coupling the free energy of GTP hydrolysis to translocation, EF-G serves as a motor protein to drive the directional movement of transfer and messenger RNAs on the ribosome.
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Affiliation(s)
- M V Rodnina
- Institute of Molecular Biology, University of Witten/Herdecke, Germany
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8
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Abstract
Protein synthesis in both eukaryotic and prokaryotic cells is a complex process requiring a large number of macromolecules: initiation factors, elongation factors, termination factors, ribosomes, mRNA, amino-acylsynthetases and tRNAs. This review focuses on our current knowledge of protein synthesis in higher plants.
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Affiliation(s)
- K S Browning
- Department of Chemistry and Biochemistry, University of Texas at Austin 78712, USA
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9
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Ayala A, Parrado J, Bougria M, Machado A. Effect of oxidative stress, produced by cumene hydroperoxide, on the various steps of protein synthesis. Modifications of elongation factor-2. J Biol Chem 1996; 271:23105-10. [PMID: 8798501 DOI: 10.1074/jbc.271.38.23105] [Citation(s) in RCA: 256] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have studied the effect of oxidative stress on protein synthesis in rat liver. Cumene hydroperoxide (CH) was used as an oxidant agent. The approach used was to determine the ribosomal state of aggregation and the time for assembly and release of polypeptide chains in the process of protein synthesis in rat liver in vivo. The results suggest that the elongation step is the most sensitive to CH treatment. The measurement of both carbonyl groups content and ADP-ribosylatable elongation factor 2 (EF-2), the main protein involved in the elongation step, indicates that under CH treatment EF-2 is oxidatively modified and a lower amount of active EF-2 is present. These results are corroborated by in vitro oxidation of EF-2 and could explain for the decline in the elongation step.
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Affiliation(s)
- A Ayala
- Departamento de Bioquimica, Bromatologia y Toxicologia, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
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Borowski C, Rodnina MV, Wintermeyer W. Truncated elongation factor G lacking the G domain promotes translocation of the 3' end but not of the anticodon domain of peptidyl-tRNA. Proc Natl Acad Sci U S A 1996; 93:4202-6. [PMID: 8633041 PMCID: PMC39512 DOI: 10.1073/pnas.93.9.4202] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The mechanism by which elongation factor G (EF-G) catalyzes the translocation of tRNAs and mRNA on the ribosome is not known. The reaction requires GTP, which is hydrolyzed to GDP. Here we show that EF-G from Escherichia coli lacking the G domain still catalyzed partial translocation in that it promoted the transfer of the 3' end of peptidyl-tRNA to the P site on the 50S ribosomal subunit into a puromycin-reactive state in a slow-turnover reaction. In contrast, it did not bring about translocation on the 30S subunit, since (i) deacylated tRNA was not released from the P site and (ii) the A site remained blocked for aminoacyl-tRNA binding during and after partial translocation. The reaction probably represents the first EF-G-dependent step of translocation that follows the spontaneous formation of the A/P state that is not puromycin-reactive [Moazed, D. & Noller, H. F. (1989) Nature (London) 342, 142-148]. In the complete system--i.e., with intact EF-G and GTP--the 50S phase of translocation is rapidly followed by the 30S phase during which the tRNAs together with the mRNA are shifted on the small ribosomal subunit, and GTP is hydrolyzed. As to the mechanism of EF-G function, the results show that the G domain has an important role, presumably exerted through interactions with other domains of EF-G, in the promotion of translocation on the small ribosomal subunit. The G domain's intramolecular interactions are likely to be modulated by GTP binding and hydrolysis.
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Affiliation(s)
- C Borowski
- Institute of Molecular Biology, University of Witten/Herdecke, Germany
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11
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Foley BT, Moehring JM, Moehring TJ. Mutations in the elongation factor 2 gene which confer resistance to diphtheria toxin and Pseudomonas exotoxin A. Genetic and biochemical analyses. J Biol Chem 1995; 270:23218-25. [PMID: 7559470 DOI: 10.1074/jbc.270.39.23218] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Both diphtheria toxin and Pseudomonas exotoxin A inhibit eukaryotic protein synthesis by ADP-ribosylating diphthamide, a posttranslationally modified histidine residue present in the elongation factor 2 (EF-2) protein. Elongation factor 2 cannot be ADP-ribosylated by the toxins unless this histidine is modified. In this report we identify three new point mutations in toxin-resistant alleles of the Chinese hamster ovary cell elongation factor 2 gene. The mutations resulted in amino acid substitutions at positions 584 (serine to glycine), 714 (isoleucine to asparagine), and 719 (glycine to aspartic acid). All three amino acid substitutions prevented the biosynthesis of diphthamide. The amount by which the toxins reduced protein synthesis in each of these mutant cell strains suggested that all three mutations also either impaired the function of EF-2 or reduced its steady state level in the cytoplasm. Western blot analysis showed that equal amounts of EF-2 were present in each of the cell strains, indicating that the mutations impaired the catalytic function of EF-2.
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Affiliation(s)
- B T Foley
- University of Vermont, Department of Microbiology and Molecular Genetics, Markey Center for Molecular Genetics, Burlington 05405, USA
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Wellner RB, Pless DD, Thompson WL. Characterization of 3'-azido-3'-deoxythymidine inhibition of ricin and Pseudomonas exotoxin A toxicity in CHO and Vero cells. J Cell Physiol 1994; 159:495-505. [PMID: 8188764 DOI: 10.1002/jcp.1041590314] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Ricin (RIC), modeccin (MOD), Pseudomonas exotoxin A (PE), and diphtheria toxin (DT) are protein toxins that enter cells by receptor-mediated endocytosis. After intracellular transport and membrane translocation to the cytosol, these toxins inhibit protein synthesis by enzymatically removing a specific adenine residue from ribosomal RNA (RIC, MOD), or by ADP-ribosylation of elongation factor-2 (PE, DT). Recently, Thompson and Pace (1992) reported that AZT (3'-azido-3'-deoxythymidine) inhibited RIC toxicity in Vero cells, and this inhibition was not due to a block of RIC enzymatic activity. This paper extends these findings and examines the effects of AZT treatment on the toxicities of other protein toxins in Chinese hamster ovary (CHO) and Vero cell lines. AZT treatment did not significantly alter the toxicity of DT or MOD in either cell line, but it markedly reduced RIC and PE toxicity in both cell lines. The ID50 values (concentration of toxin required to inhibit protein synthesis by 50%) for RIC and PE in CHO cells increased approximately 6.5- and 12.5-fold, respectively; while in Vero cells the ID50 values increased ca. 8.5- and 4.5-fold, respectively. Results of further studies revealed differences in the mechanisms by which AZT inhibited RIC and PE toxicity. Results of cell-free translation indicated that, unlike its effects on RIC, AZT blocked the ability of PE to perform its enzymatic activity. As AZT did not block RIC enzymatic activity, we examined the effects of AZT on earlier steps in the RIC intoxication process. AZT treatment did not inhibit cell-surface binding or internalization of [125I]-RIC. Results of kinetic studies showed that when AZT was incubated with cells at the time of RIC exposure, it caused no major change in the lag phase, during which RIC reaches the site of translocation. However, it clearly reduced the subsequent first-order reduction in the rate of protein synthesis, suggesting an effect on translocation. Monensin (an ionophore that perturbs intracellular trafficking and increases the toxicities of RIC and PE) reduced AZT protection against both toxins. Nocodazole and colchicine (agents that disrupt microtubules and some routes of intracellular trafficking) reduced the ability of AZT to inhibit RIC, but not PE, toxicity. In summary, our results suggest that (1) AZT acts within the cytosol to inhibit (directly or indirectly) the enzymatic action of PE, and (2) the AZT inhibition of RIC cytotoxicity does not involve perturbations of RIC cell-surface binding, internalization, or enzymatic activity but might result from an alteration in RIC translocation.
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Affiliation(s)
- R B Wellner
- Toxinology Division, U.S. Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21702-5011
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13
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Kimata Y, Kohno K. Elongation factor 2 mutants deficient in diphthamide formation show temperature-sensitive cell growth. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36859-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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14
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Phan L, Perentesis J, Bodley J. Saccharomyces cerevisiae elongation factor 2. Mutagenesis of the histidine precursor of diphthamide yields a functional protein that is resistant to diphtheria toxin. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)52926-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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15
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DPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae. Mol Cell Biol 1992. [PMID: 1508200 DOI: 10.1128/mcb.12.9.4026] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A mutant of Saccharomyces cerevisiae defective in the S-adenosylmethionine (AdoMet)-dependent methyltransferase step of diphthamide biosynthesis was selected by intracellular expression of the F2 fragment of diphtheria toxin (DT) and shown to belong to complementation group DPH5. The DPH5 gene was cloned, sequenced, and found to encode a 300-residue protein with sequence similarity to bacterial AdoMet:uroporphyrinogen III methyltransferases, enzymes involved in cobalamin (vitamin B12) biosynthesis. Both DPH5 and AdoMet:uroporphyrinogen III methyltransferases lack sequence motifs commonly found in other methyltransferases and may represent a new family of AdoMet:methyltransferases. The DPH5 protein was produced in Escherichia coli and shown to be active in methylation of elongation factor 2 partially purified from the dph5 mutant. A null mutation of the chromosomal DPH5 gene did not affect cell viability, in agreement with other studies indicating that diphthamide is not required for cell survival. The dph5 null mutant survived expression of three enzymically attenuated DT fragments but was killed by expression of fully active DT fragment A. Consistent with these results, elongation factor 2 from the dph5 null mutant was found to have weak ADP-ribosyl acceptor activity, which was detectable only in the presence of high concentrations of fragment A.
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Mattheakis LC, Shen WH, Collier RJ. DPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae. Mol Cell Biol 1992; 12:4026-37. [PMID: 1508200 PMCID: PMC360293 DOI: 10.1128/mcb.12.9.4026-4037.1992] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A mutant of Saccharomyces cerevisiae defective in the S-adenosylmethionine (AdoMet)-dependent methyltransferase step of diphthamide biosynthesis was selected by intracellular expression of the F2 fragment of diphtheria toxin (DT) and shown to belong to complementation group DPH5. The DPH5 gene was cloned, sequenced, and found to encode a 300-residue protein with sequence similarity to bacterial AdoMet:uroporphyrinogen III methyltransferases, enzymes involved in cobalamin (vitamin B12) biosynthesis. Both DPH5 and AdoMet:uroporphyrinogen III methyltransferases lack sequence motifs commonly found in other methyltransferases and may represent a new family of AdoMet:methyltransferases. The DPH5 protein was produced in Escherichia coli and shown to be active in methylation of elongation factor 2 partially purified from the dph5 mutant. A null mutation of the chromosomal DPH5 gene did not affect cell viability, in agreement with other studies indicating that diphthamide is not required for cell survival. The dph5 null mutant survived expression of three enzymically attenuated DT fragments but was killed by expression of fully active DT fragment A. Consistent with these results, elongation factor 2 from the dph5 null mutant was found to have weak ADP-ribosyl acceptor activity, which was detectable only in the presence of high concentrations of fragment A.
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Affiliation(s)
- L C Mattheakis
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
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Abstract
The combination of genetic, molecular and biochemical approaches have made the yeast Saccharomyces cerevisiae a convenient organism to study translation. The sequence similarity of translation factors from yeast and other organisms suggests a high degree of conservation in the translational machineries. This view is also strengthened by a functional analogy of some proteins implicated in translation. Beautiful genetic experiments have confirmed existing models and added new insights in the mechanism of translation. This review summarizes recent experiments using yeast as a model system for the analysis of this complex process.
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Affiliation(s)
- P Linder
- Department of Microbiology, Biozentrum, Basel, Switzerland
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Abstract
This review presents a description of the numerous eukaryotic protein synthesis factors and their apparent sequential utilization in the processes of initiation, elongation, and termination. Additionally, the rare use of reinitiation and internal initiation is discussed, although little is known biochemically about these processes. Subsequently, control of translation is addressed in two different settings. The first is the global control of translation, which is effected by protein phosphorylation. The second is a series of specific mRNAs for which there is a direct and unique regulation of the synthesis of the gene product under study. Other examples of translational control are cited but not discussed, because the general mechanism for the regulation is unknown. Finally, as is often seen in an active area of investigation, there are several observations that cannot be readily accommodated by the general model presented in the first part of the review. Alternate explanations and various lines of experimentation are proposed to resolve these apparent contradictions.
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Affiliation(s)
- W C Merrick
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
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Abstract
The molecular events responsible for controlling cell growth and development, as well as their coordinate interaction is only beginning to be revealed. At the basis of these controlling events are hormones, growth factors and mitogens which, through transmembrane signalling trigger an array of cellular responses, initiated by receptor-associated tyrosine kinases, which in turn either directly or indirectly mediate their effects through serine/threonine protein kinases. Utilizing the obligatory response of activation of protein synthesis in cell growth and development, we describe efforts to work backwards along the regulatory pathway to the receptor, identifying those molecular components involved in modulating the rate of translation. We begin by describing the components and steps of protein synthesis and then discuss in detail the regulatory pathways involved in the mitogenic response of eukaryotic cells and during meiotic maturation of oocytes. Finally we discuss possible future work which will further our understanding of these systems.
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Affiliation(s)
- S J Morley
- Friedrich Miescher-Institut, Basel, Switzerland
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20
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Abstract
In eukaryotes, peptide chain elongation is mediated by elongation factors EF-1 and EF-2. EF-1 is composed of a nucleotide-binding protein EF-1 alpha, and a nucleotide exchange protein complex, EF-1 beta gamma, while EF-2 catalyses the translocation of peptidyl-tRNA on the ribosome. Elongation factors are highly conserved among different species and may be involved in functions other than protein synthesis, such as organization of the mitotic apparatus, signal transduction, developmental regulation, ageing and transformation. Yeast contains a third factor, EF-3, whose structure and function is not yet well understood.
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Affiliation(s)
- B Riis
- Department of Chemistry, Aarhus University, Denmark
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21
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Dordick JS. Protein engineering and site-directed mutagenesis. Patents and literature. Appl Biochem Biotechnol 1990; 26:107-13. [PMID: 2268144 DOI: 10.1007/bf02798396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- J S Dordick
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, 52242
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22
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Nygård O, Nilsson L. Translational dynamics. Interactions between the translational factors, tRNA and ribosomes during eukaryotic protein synthesis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 191:1-17. [PMID: 2199194 DOI: 10.1111/j.1432-1033.1990.tb19087.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- O Nygård
- Department of Cell Biology, Wenner-Gren Institute, University of Stockholm, Sweden
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23
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Lavergne JP, Marzouki A, Reboud AM, Reboud JP. Modification of the reactivity of three amino-acid residues in elongation factor 2 during its binding to ribosomes and translocation. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1048:231-7. [PMID: 2322578 DOI: 10.1016/0167-4781(90)90061-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The accessibility of three amino acids of EF-2, located within highly conserved regions near the N- and C-terminal extremities of the molecule (the E region and the ADPR region, respectively) to modifying enzymes has been compared within nucleotide-complexed EF-2 and ribosomal complexes that mimic the pre- and posttranslocational ones: the high-affinity complex (EF-2)-nonhydrolysable GTP analog GuoPP[CH2]P ribosome and the low-affinity (EF-2)-GDP-ribosome complex, EF-2 and ribosomes being from rat liver. We studied the reactivity of two highly conserved residues diphthamide-715 and Arg-66, to diphtheria-toxin-dependent ADP-ribosylation and trypsin attack, and of a threonine that probably lies between residues 51 and 60, to phosphorylation by a Ca2+/calmodulin-dependent protein kinase. Diphthamide 715 and this threonine residue were unreactive within the high-affinity complex but seemed fully reactive in the low-affinity complex. Arg-66 was resistant to trypsin in both complexes. The possible involvement of the E and ADPR regions of EF-2 in the interaction with ribosome in the two complexes is discussed.
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Affiliation(s)
- J P Lavergne
- Laboratoire de Biochimie Médicale, Université Claude Bernard, Villeurbanne, France
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24
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Nygård O, Nilsson L. Kinetic determination of the effects of ADP-ribosylation on the interaction of eukaryotic elongation factor 2 with ribosomes. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39286-5] [Citation(s) in RCA: 15] [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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Dever T, Costello C, Owens C, Rosenberry T, Merrick W. Location of Seven Post-translational Modifications in Rabbit Elongation Factor 1α Including Dimethyllysine, Trimethyllysine, and Glycerylphosphorylethanolamine. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)47093-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Riis B, Rattan SI, Clark BF. Estimating the amounts of ADP-ribosylatable active elongation factor-2 in mammalian cell-free extracts. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 1989; 19:319-25. [PMID: 2693515 DOI: 10.1016/0165-022x(89)90063-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The content of the elongation factor (EF-2) can be measured by diphtheria toxin-dependent ADP-ribosylation in cell-free extracts of samples prepared from small amounts of tissues and cells containing less than 100 micrograms of total protein. A 20 min in vitro assay, in which a radioactive ADP-ribosyl residue is transferred specifically and 1:1 stoichiometrically to EF-2, is sufficient to estimate the total amounts of ADP-ribosylatable active EF-2. The method is very useful for monitoring changing levels of EF-2 during various pathological and biological processes, including cell cycle, ageing, cancer and other diseases.
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Affiliation(s)
- B Riis
- Department of Chemistry, Aarhus University, Denmark
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Abstract
The high heterogeneity of native rat liver EF-2 prepared from either 105000 x g supernatant or microsome high-salt extract was detected by two-dimensional equilibrium isoelectric focusing-SDS-polyacrylamide gel electrophoresis in the presence of 9.5 M urea. Five spots were always detected, all of Mr 95,000, which were not artefactual for their amount varied when EF-2 was specifically ADP-ribosylated by diphtheria toxin in the presence of NAD+, and/or phosphorylated on a threonine residue by a Ca2+/calmodulin-dependent protein kinase (most likely Ca2+/calmodulin-dependent protein kinase III described by others [(1987) J. Biol. Chem. 262, 17299-17303; (1988) Nature 334, 170-173]). Results of ADP-ribosylation and/or phosphorylation experiments with either unlabeled or labeled reagents ([14C]NAD and [32P]ATP) strongly suggest that our preparation contained native ADP-ribosylated and native phosphorylated forms which could be estimated at about 20% and 40% of the whole EF-2. Phosphorylated and ADP-ribosylated forms of EF-2 could be ADP-ribosylated and phosphorylated, respectively, but a native form both ADP-ribosylated and phosphorylated was not detected. Our results also suggest the existence of a minor native form of EF-2 and of its phosphorylated and ADP-ribosylated derivatives.
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Affiliation(s)
- A Marzouki
- Laboratoire de Biochimie Médicale, Université Lyon I, UM CNRS 24, Villeurbanne, France
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