1
|
Ütkür K, Mayer K, Liu S, Brinkmann U, Schaffrath R. Functional Integrity of Radical SAM Enzyme Dph1•Dph2 Requires Non-Canonical Cofactor Motifs with Tandem Cysteines. Biomolecules 2024; 14:470. [PMID: 38672486 PMCID: PMC11048331 DOI: 10.3390/biom14040470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/05/2024] [Accepted: 04/09/2024] [Indexed: 04/28/2024] Open
Abstract
The Dph1•Dph2 heterodimer from yeast is a radical SAM (RS) enzyme that generates the 3-amino-3-carboxy-propyl (ACP) precursor for diphthamide, a clinically relevant modification on eukaryotic elongation factor 2 (eEF2). ACP formation requires SAM cleavage and atypical Cys-bound Fe-S clusters in each Dph1 and Dph2 subunit. Intriguingly, the first Cys residue in each motif is found next to another ill-defined cysteine that we show is conserved across eukaryotes. As judged from structural modeling, the orientation of these tandem cysteine motifs (TCMs) suggests a candidate Fe-S cluster ligand role. Hence, we generated, by site-directed DPH1 and DPH2 mutagenesis, Dph1•Dph2 variants with cysteines from each TCM replaced individually or in combination by serines. Assays diagnostic for diphthamide formation in vivo reveal that while single substitutions in the TCM of Dph2 cause mild defects, double mutations almost entirely inactivate the RS enzyme. Based on enhanced Dph1 and Dph2 subunit instability in response to cycloheximide chases, the variants with Cys substitutions in their cofactor motifs are particularly prone to protein degradation. In sum, we identify a fourth functionally cooperative Cys residue within the Fe-S motif of Dph2 and show that the Cys-based cofactor binding motifs in Dph1 and Dph2 are critical for the structural integrity of the dimeric RS enzyme in vivo.
Collapse
Affiliation(s)
- Koray Ütkür
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany;
| | - Klaus Mayer
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, 82377 Penzberg, Germany; (K.M.); (U.B.)
| | - Shihui Liu
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA;
| | - Ulrich Brinkmann
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, 82377 Penzberg, Germany; (K.M.); (U.B.)
| | - Raffael Schaffrath
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany;
| |
Collapse
|
2
|
Schaffrath R, Brinkmann U. Diphthamide - a conserved modification of eEF2 with clinical relevance. Trends Mol Med 2024; 30:164-177. [PMID: 38097404 DOI: 10.1016/j.molmed.2023.11.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 11/03/2023] [Accepted: 11/09/2023] [Indexed: 02/17/2024]
Abstract
Diphthamide, a complex modification on eukaryotic translation elongation factor 2 (eEF2), assures reading-frame fidelity during translation. Diphthamide and enzymes for its synthesis are conserved in eukaryotes and archaea. Originally identified as target for diphtheria toxin (DT) in humans, its clinical relevance now proves to be broader than the link to pathogenic bacteria. Diphthamide synthesis enzymes (DPH1 and DPH3) are associated with cancer, and DPH gene mutations can cause diphthamide deficiency syndrome (DDS). Finally, new analyses provide evidence that diphthamide may restrict propagation of viruses including SARS-CoV-2 and HIV-1, and that DPH enzymes are targeted by viruses for degradation to overcome this restriction. This review describes how diphthamide is synthesized and functions in translation, and covers its clinical relevance in human development, cancer, and infectious diseases.
Collapse
Affiliation(s)
- Raffael Schaffrath
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, Kassel, Germany.
| | - Ulrich Brinkmann
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, Penzberg, Germany.
| |
Collapse
|
3
|
Ütkür K, Mayer K, Khan M, Manivannan T, Schaffrath R, Brinkmann U. DPH1 and DPH2 variants that confer susceptibility to diphthamide deficiency syndrome in human cells and yeast models. Dis Model Mech 2023; 16:dmm050207. [PMID: 37675463 PMCID: PMC10538292 DOI: 10.1242/dmm.050207] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 08/21/2023] [Indexed: 09/08/2023] Open
Abstract
The autosomal-recessive diphthamide deficiency syndrome presents as intellectual disability with developmental abnormalities, seizures, craniofacial and additional morphological phenotypes. It is caused by reduced activity of proteins that synthesize diphthamide on human translation elongation factor 2. Diphthamide synthesis requires seven proteins (DPH1-DPH7), with clinical deficiency described for DPH1, DPH2 and DPH5. A limited set of variant alleles from syndromic patients has been functionally analyzed, but databases (gnomAD) list additional so far uncharacterized variants in human DPH1 and DPH2. Because DPH enzymes are conserved among eukaryotes, their functionality can be assessed in yeast and mammalian cells. Our experimental assessment of known and uncharacterized DPH1 and DPH2 missense alleles showed that six variants are tolerated despite inter-species conservation. Ten additional human DPH1 (G113R, A114T, H132P, H132R, S136R, C137F, L138P, Y152C, S221P, H240R) and two DPH2 (H105P, C341Y) variants showed reduced functionality and hence are deficiency-susceptibility alleles. Some variants locate close to the active enzyme center and may affect catalysis, while others may impact on enzyme activation. In sum, our study has identified functionally compromised alleles of DPH1 and DPH2 genes that likely cause diphthamide deficiency syndrome.
Collapse
Affiliation(s)
- Koray Ütkür
- Institut für Biologie,Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany
| | - Klaus Mayer
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, 82377 Penzberg, Germany
| | - Maliha Khan
- Institut für Biologie,Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany
| | - Thirishika Manivannan
- Institut für Biologie,Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany
| | - Raffael Schaffrath
- Institut für Biologie,Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany
| | - Ulrich Brinkmann
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, 82377 Penzberg, Germany
| |
Collapse
|
4
|
Hawer H, Mendelsohn BA, Mayer K, Kung A, Malhotra A, Tuupanen S, Schleit J, Brinkmann U, Schaffrath R. Diphthamide-deficiency syndrome: a novel human developmental disorder and ribosomopathy. Eur J Hum Genet 2020; 28:1497-1508. [PMID: 32576952 PMCID: PMC7575589 DOI: 10.1038/s41431-020-0668-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 04/06/2020] [Accepted: 05/28/2020] [Indexed: 02/06/2023] Open
Abstract
We describe a novel type of ribosomopathy that is defined by deficiency in diphthamidylation of translation elongation factor 2. The ribosomopathy was identified by correlating phenotypes and biochemical properties of previously described patients with diphthamide biosynthesis gene 1 (DPH1) deficiencies with a new patient that carried inactivating mutations in both alleles of the human diphthamide biosynthesis gene 2 (DPH2). The human DPH1 syndrome is an autosomal recessive disorder associated with developmental delay, abnormal head circumference (microcephaly or macrocephaly), short stature, and congenital heart disease. It is defined by variants with reduced functionality of the DPH1 gene observed so far predominantly in consanguineous homozygous patients carrying identical mutant alleles of DPH1. Here we report a child with a very similar phenotype carrying biallelic variants of the human DPH2. The gene products DPH1 and DPH2 are components of a heterodimeric enzyme complex that mediates the first step of the posttranslational diphthamide modification on the nonredundant eukaryotic translation elongation factor 2 (eEF2). Diphthamide deficiency was shown to reduce the accuracy of ribosomal protein biosynthesis. Both DPH2 variants described here severely impair diphthamide biosynthesis as demonstrated in human and yeast cells. This is the first report of a patient carrying compound heterozygous DPH2 loss-of-function variants with a DPH1 syndrome-like phenotype and implicates diphthamide deficiency as the root cause of this patient's clinical phenotype as well as of DPH1-syndrome. These findings define "diphthamide-deficiency syndrome" as a special ribosomopathy due to reduced functionality of components of the cellular machinery for eEF2-diphthamide synthesis.
Collapse
Affiliation(s)
- Harmen Hawer
- Fachgebiet Mikrobiologie, Institut für Biologie, Universität Kassel, D-34132, Kassel, Hessen, Germany
| | | | - Klaus Mayer
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, D-82377, Penzberg, Bavaria, Germany
| | - Ann Kung
- Kaiser Permanente Oakland Medical Center, Oakland, CA, 94611, USA
| | - Amit Malhotra
- Kaiser Permanente Oakland Medical Center, Oakland, CA, 94611, USA
| | - Sari Tuupanen
- Blueprint Genetics Oy, Keilaranta 16 A-B, 02150, Espoo, Finland
| | | | - Ulrich Brinkmann
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, D-82377, Penzberg, Bavaria, Germany.
| | - Raffael Schaffrath
- Fachgebiet Mikrobiologie, Institut für Biologie, Universität Kassel, D-34132, Kassel, Hessen, Germany
| |
Collapse
|
5
|
Liu J, Zuo Z, Zou M, Finkel T, Liu S. Identification of the transcription factor Miz1 as an essential regulator of diphthamide biosynthesis using a CRISPR-mediated genome-wide screen. PLoS Genet 2020; 16:e1009068. [PMID: 33057331 PMCID: PMC7591051 DOI: 10.1371/journal.pgen.1009068] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 10/27/2020] [Accepted: 08/20/2020] [Indexed: 12/15/2022] Open
Abstract
Diphthamide is a unique post-translationally modified histidine residue (His715 in all mammals) found only in eukaryotic elongation factor-2 (eEF-2). The biosynthesis of diphthamide represents one of the most complex modifications, executed by protein factors conserved from yeast to humans. Diphthamide is not only essential for normal physiology (such as ensuring fidelity of mRNA translation), but is also exploited by bacterial ADP-ribosylating toxins (e.g., diphtheria toxin) as their molecular target in pathogenesis. Taking advantage of the observation that cells defective in diphthamide biosynthesis are resistant to ADP-ribosylating toxins, in the past four decades, seven essential genes (Dph1 to Dph7) have been identified for diphthamide biosynthesis. These technically unsaturated screens raise the question as to whether additional genes are required for diphthamide biosynthesis. In this study, we performed two independent, saturating, genome-wide CRISPR knockout screens in human cells. These screens identified all previously known Dph genes, as well as further identifying the BTB/POZ domain-containing transcription factor Miz1. We found that Miz1 is absolutely required for diphthamide biosynthesis via its role in the transcriptional regulation of Dph1 expression. Mechanistically, Miz1 binds to the Dph1 proximal promoter via an evolutionarily conserved consensus binding site to activate Dph1 transcription. Therefore, this work demonstrates that Dph1-7, along with the newly identified Miz1 transcription factor, are likely to represent the essential protein factors required for diphthamide modification on eEF2. Diphthamide is a unique post-translationally modified histidine residue (His699 in yeast, His715 in all mammals) found only in eukaryotic elongation factor-2 (eEF-2). Mice that are deficient in diphthamide biosynthesis are embryonic lethal, attesting to the importance of diphthamide in normal physiology. It has taken four decades to identify the seven non-redundant genes in diphthamide biosynthesis, but whether additional factors are required and how the pathway is regulated remained elusive. To address these issues, we performed two saturating, independent, and unbiased genome-wide CRISPR knockout screens. The screens concluded independently that Dph1-Dph7 and additionally transcription factor Miz1 are the key factors required for diphthamide biosynthesis. Mechanistically, Miz1 binds to the Dph1 proximal promoter via an evolutionarily conserved consensus binding site to activate Dph1 transcription. While diphthamide biosynthesis machinery (Dph1-Dph7) exists across eukaryotes, Miz1 orthologues do not exist in lower species such as yeast, C. elegans, and Drosophila, indicating that the regulation of diphthamide modification by Miz1 emerged much later in evolution. The work opens a new avenue for understanding the role that diphthamide modification plays in normal physiology and bacterial toxin pathogenesis.
Collapse
Affiliation(s)
- Jie Liu
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Zehua Zuo
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
| | - Meijuan Zou
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
| | - Toren Finkel
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Shihui Liu
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
- * E-mail:
| |
Collapse
|
6
|
Togami K, Pastika T, Stephansky J, Ghandi M, Christie AL, Jones KL, Johnson CA, Lindsay RW, Brooks CL, Letai A, Craig JW, Pozdnyakova O, Weinstock DM, Montero J, Aster JC, Johannessen CM, Lane AA. DNA methyltransferase inhibition overcomes diphthamide pathway deficiencies underlying CD123-targeted treatment resistance. J Clin Invest 2020; 129:5005-5019. [PMID: 31437130 DOI: 10.1172/jci128571] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 08/13/2019] [Indexed: 12/16/2022] Open
Abstract
The interleukin-3 receptor α subunit, CD123, is expressed in many hematologic malignancies including acute myeloid leukemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN). Tagraxofusp (SL-401) is a CD123-targeted therapy consisting of interleukin-3 fused to a truncated diphtheria toxin payload. Factors influencing response to tagraxofusp other than CD123 expression are largely unknown. We interrogated tagraxofusp resistance in patients and experimental models and found that it was not associated with CD123 loss. Rather, resistant AML and BPDCN cells frequently acquired deficiencies in the diphthamide synthesis pathway, impairing tagraxofusp's ability to ADP-ribosylate cellular targets. Expression of DPH1, encoding a diphthamide pathway enzyme, was reduced by DNA CpG methylation in resistant cells. Treatment with the DNA methyltransferase inhibitor azacitidine restored DPH1 expression and tagraxofusp sensitivity. We also developed a drug-dependent ADP-ribosylation assay in primary cells that correlated with tagraxofusp activity and may represent an additional novel biomarker. As predicted by these results and our observation that resistance also increased mitochondrial apoptotic priming, we found that the combination of tagraxofusp and azacitidine was effective in patient-derived xenografts treated in vivo. These data have important implications for clinical use of tagraxofusp and led to a phase 1 study combining tagraxofusp and azacitidine in myeloid malignancies.
Collapse
Affiliation(s)
- Katsuhiro Togami
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Timothy Pastika
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Jason Stephansky
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Mahmoud Ghandi
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
| | - Amanda L Christie
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Kristen L Jones
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Carl A Johnson
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | | | | | - Anthony Letai
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Jeffrey W Craig
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Olga Pozdnyakova
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - David M Weinstock
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Joan Montero
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - Jon C Aster
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Andrew A Lane
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
| |
Collapse
|
7
|
Lange MJ, Lyddon TD, Johnson MC. Diphtheria Toxin A-Resistant Cell Lines Enable Robust Production and Evaluation of DTA-Encoding Lentiviruses. Sci Rep 2019; 9:8985. [PMID: 31222087 PMCID: PMC6586843 DOI: 10.1038/s41598-019-45481-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 06/06/2019] [Indexed: 02/06/2023] Open
Abstract
Suicide genes have been widely investigated for their utility as therapeutic agents and as tools for in vitro negative selection strategies. Several methods for delivery of suicide genes have been explored. Two important considerations for delivery are the quantity of delivered cargo and the ability to target the cargo to specific cells. Delivery using a lentiviral vector is particularly attractive due to the ability to encode the gene within the viral genome, as well as the ability to limit off-target effects by using cell type-specific glycoproteins. Here, we present the design and validation of a diphtheria toxin A (DTA)-encoding lentiviral vector expressing DTA under the control of a constituitive promoter to allow for expression of DTA in a variety of cell types, with specificity provided via selection of glycoproteins for pseudotyping of the lentiviral particles. DTA exerts its toxic activity through inhibition of eukaryotic translation elongation factor 2 (eEF2) via adenosine diphosphate (ADP)-ribosylation of a modified histidine residue, diphthamide, at His715, which blocks protein translation and leads to cell death. Thus, we also detail development of DTA-resistant cell lines, engineered through CRISPR/Cas9-mediated knockout of the diphthamide 1 (DPH1) gene, which enable both robust virus production by transfection and evaluation of DTA-expressing virus infectivity.
Collapse
Affiliation(s)
- Margaret J Lange
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA. .,Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA. .,Department of Molecular Microbiology & Immunology, Bond Life Sciences Center, University of Missouri, Columbia, MO, 65211, United States.
| | - Terri D Lyddon
- Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
| | - Marc C Johnson
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA. .,Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA. .,Department of Molecular Microbiology & Immunology, Bond Life Sciences Center, University of Missouri, Columbia, MO, 65211, United States.
| |
Collapse
|
8
|
Mayer K, Mundigl O, Kettenberger H, Birzele F, Stahl S, Pastan I, Brinkmann U. Diphthamide affects selenoprotein expression: Diphthamide deficiency reduces selenocysteine incorporation, decreases selenite sensitivity and pre-disposes to oxidative stress. Redox Biol 2019; 20:146-156. [PMID: 30312900 PMCID: PMC6180344 DOI: 10.1016/j.redox.2018.09.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 09/17/2018] [Accepted: 09/24/2018] [Indexed: 12/31/2022] Open
Abstract
The diphthamide modification of translation elongation factor 2 is highly conserved in eukaryotes and archaebacteria. Nevertheless, cells lacking diphthamide can carry out protein synthesis and are viable. We have analyzed the phenotypes of diphthamide deficient cells and found that diphthamide deficiency reduces selenocysteine incorporation into selenoproteins. Additional phenotypes resulting from diphthamide deficiency include altered tRNA-synthetase and selenoprotein transcript levels, hypersensitivity to oxidative stress and increased selenite tolerance. Diphthamide-eEF2 occupies the aminoacyl-tRNA translocation site at which UGA either stalls translation or decodes selenocysteine. Its position is in close proximity and mutually exclusive to the ribosomal binding site of release/recycling factor ABCE1, which harbors a redox-sensitive Fe-S cluster and, like diphthamide, is present in eukaryotes and archaea but not in eubacteria. Involvement of diphthamide in UGA-SECIS decoding may explain deregulated selenoprotein expression and as a consequence oxidative stress, NFkB activation and selenite tolerance in diphthamide deficient cells.
Collapse
Affiliation(s)
- Klaus Mayer
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Penzberg, Germany
| | - Olaf Mundigl
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Penzberg, Germany
| | - Hubert Kettenberger
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Penzberg, Germany
| | - Fabian Birzele
- Roche Pharma Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Basel, Switzerland
| | - Sebastian Stahl
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Penzberg, Germany
| | - Ira Pastan
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Ulrich Brinkmann
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Penzberg, Germany.
| |
Collapse
|
9
|
Roles of Elongator Dependent tRNA Modification Pathways in Neurodegeneration and Cancer. Genes (Basel) 2018; 10:genes10010019. [PMID: 30597914 PMCID: PMC6356722 DOI: 10.3390/genes10010019] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 12/18/2018] [Accepted: 12/20/2018] [Indexed: 02/07/2023] Open
Abstract
Transfer RNA (tRNA) is subject to a multitude of posttranscriptional modifications which can profoundly impact its functionality as the essential adaptor molecule in messenger RNA (mRNA) translation. Therefore, dynamic regulation of tRNA modification in response to environmental changes can tune the efficiency of gene expression in concert with the emerging epitranscriptomic mRNA regulators. Several of the tRNA modifications are required to prevent human diseases and are particularly important for proper development and generation of neurons. In addition to the positive role of different tRNA modifications in prevention of neurodegeneration, certain cancer types upregulate tRNA modification genes to sustain cancer cell gene expression and metastasis. Multiple associations of defects in genes encoding subunits of the tRNA modifier complex Elongator with human disease highlight the importance of proper anticodon wobble uridine modifications (xm⁵U34) for health. Elongator functionality requires communication with accessory proteins and dynamic phosphorylation, providing regulatory control of its function. Here, we summarized recent insights into molecular functions of the complex and the role of Elongator dependent tRNA modification in human disease.
Collapse
|
10
|
Abstract
Transition state theory teaches that chemically stable mimics of enzymatic transition states will bind tightly to their cognate enzymes. Kinetic isotope effects combined with computational quantum chemistry provides enzymatic transition state information with sufficient fidelity to design transition state analogues. Examples are selected from various stages of drug development to demonstrate the application of transition state theory, inhibitor design, physicochemical characterization of transition state analogues, and their progress in drug development.
Collapse
Affiliation(s)
- Vern L. Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| |
Collapse
|
11
|
Hawer H, Ütkür K, Arend M, Mayer K, Adrian L, Brinkmann U, Schaffrath R. Importance of diphthamide modified EF2 for translational accuracy and competitive cell growth in yeast. PLoS One 2018; 13:e0205870. [PMID: 30335802 PMCID: PMC6193676 DOI: 10.1371/journal.pone.0205870] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/02/2018] [Indexed: 01/23/2023] Open
Abstract
In eukaryotes, the modification of an invariant histidine (His-699 in yeast) residue in translation elongation factor 2 (EF2) with diphthamide involves a conserved pathway encoded by the DPH1-DPH7 gene network. Diphthamide is the target for diphtheria toxin and related lethal ADP ribosylases, which collectively kill cells by inactivating the essential translocase function of EF2 during mRNA translation and protein biosynthesis. Although this notion emphasizes the pathological importance of diphthamide, precisely why cells including our own require EF2 to carry it, is unclear. Mining the synthetic genetic array (SGA) landscape from the budding yeast Saccharomyces cerevisiae has revealed negative interactions between EF2 (EFT1-EFT2) and diphthamide (DPH1-DPH7) gene deletions. In line with these correlations, we confirm in here that loss of diphthamide modification (dphΔ) on EF2 combined with EF2 undersupply (eft2Δ) causes synthetic growth phenotypes in the composite mutant (dphΔ eft2Δ). These reflect negative interference with cell performance under standard as well as thermal and/or chemical stress conditions, cell growth rates and doubling times, competitive fitness, cell viability in the presence of TOR inhibitors (rapamycin, caffeine) and translation indicator drugs (hygromycin, anisomycin). Together with significantly suppressed tolerance towards EF2 inhibition by cytotoxic DPH5 overexpression and increased ribosomal -1 frame-shift errors in mutants lacking modifiable pools of EF2 (dphΔ, dphΔ eft2Δ), our data indicate that diphthamide is important for the fidelity of the EF2 translocation function during mRNA translation.
Collapse
Affiliation(s)
- Harmen Hawer
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, Kassel, Germany
| | - Koray Ütkür
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, Kassel, Germany
| | - Meike Arend
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, Kassel, Germany
| | - Klaus Mayer
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center München, Penzberg, Germany
| | - Lorenz Adrian
- AG Geobiochemie, Department Isotopenbiogeochemie, Helmholtz-Zentrum für Umweltforschung GmbH–UFZ, Leipzig, Germany
- Fachgebiet Geobiotechnologie, Technische Universität Berlin, Berlin, Germany
| | - Ulrich Brinkmann
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center München, Penzberg, Germany
| | - Raffael Schaffrath
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, Kassel, Germany
- * E-mail:
| |
Collapse
|
12
|
Mayer K, Schröder A, Schnitger J, Stahl S, Brinkmann U. Influence of DPH1 and DPH5 Protein Variants on the Synthesis of Diphthamide, the Target of ADPRibosylating Toxins. Toxins (Basel) 2017; 9:E78. [PMID: 28245596 PMCID: PMC5371833 DOI: 10.3390/toxins9030078] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 02/20/2017] [Indexed: 01/22/2023] Open
Abstract
The diphthamide on eukaryotic translation elongation factor 2 (eEF2) is the target of ADPribosylating toxins and -derivatives that serve as payloads in targeted tumor therapy. Diphthamide is generated by seven DPH proteins; cells deficient in these (DPHko) lack diphthamide and are toxin-resistant. We have established assays to address the functionality of DPH1 (OVCA1) and DPH5 variants listed in dbSNP and cosmic databases: plasmids encoding wildtype and mutant DPHs were transfected into DPHko cells. Supplementation of DPH1 and DPH5 restores diphthamide synthesis and toxin sensitivity in DPH1ko and DPH5ko cells, respectively. Consequently, the determination of the diphthamide status of cells expressing DPH variants differentiates active and compromised proteins. The DPH1 frameshift variant L96fs* (with Nterminal 96 amino acids, truncated thereafter) and two splice isoforms lacking 80 or 140 amino acids at their N-termini failed to restore DPH1ko deficiency. The DPH1 frameshift variant R312fs* retained some residual activity even though it lacks a large C-terminal portion. DPH1 missense variants R27W and S56F retained activity while S221P had reduced activity, indicated by a decreased capability to restore diphthamide synthesis. The DPH5 nonsense or frameshift variants E60*, W136fs* and R207* (containing intact N-termini with truncations after 60, 136 or 207 amino acids, respectively) were inactive: none compensated the deficiency of DPH5ko cells. In contrast, missense variants D57G, G87R, S123C and Q170H as well as the frequently occurring DPH5 isoform delA212 retained activity. Sensitivity to ADP-ribosylating toxins and tumor-targeted immunotoxins depends on diphthamide which, in turn, requires DPH functionality. Because of that, DPH variants (in particular those that are functionally compromised) may serve as a biomarker and correlate with the efficacy of immunotoxin-based therapies.
Collapse
Affiliation(s)
- Klaus Mayer
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Nonnenwald 2, 82377 Penzberg, Germany.
| | - Anna Schröder
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Nonnenwald 2, 82377 Penzberg, Germany.
| | - Jerome Schnitger
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Nonnenwald 2, 82377 Penzberg, Germany.
| | - Sebastian Stahl
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Nonnenwald 2, 82377 Penzberg, Germany.
| | - Ulrich Brinkmann
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, Nonnenwald 2, 82377 Penzberg, Germany.
| |
Collapse
|
13
|
Denisova E, Heidenreich B, Nagore E, Rachakonda PS, Hosen I, Akrap I, Traves V, García-Casado Z, López-Guerrero JA, Requena C, Sanmartin O, Serra-Guillén C, Llombart B, Guillén C, Ferrando J, Gimeno E, Nordheim A, Hemminki K, Kumar R. Frequent DPH3 promoter mutations in skin cancers. Oncotarget 2016; 6:35922-30. [PMID: 26416425 PMCID: PMC4742151 DOI: 10.18632/oncotarget.5771] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 09/12/2015] [Indexed: 12/24/2022] Open
Abstract
Recent reports suggested frequent occurrence of cancer associated somatic mutations within regulatory elements of the genome. Based on initial exome sequencing of 21 melanomas, we report frequent somatic mutations in skin cancers in a bidirectional promoter of diphthamide biosynthesis 3 (DPH3) and oxidoreductase NAD-binding domain containing 1 (OXNAD1) genes. The UV-signature mutations occurred at sites adjacent and within a binding motif for E-twenty six/ternary complex factors (Ets/TCF), at -8 and -9 bp from DPH3 transcription start site. Follow up screening of 586 different skin lesions showed that the DPH3 promoter mutations were present in melanocytic nevi (2/114; 2%), melanoma (30/304; 10%), basal cell carcinoma of skin (BCC; 57/137; 42%) and squamous cell carcinoma of skin (SCC; 12/31; 39%). Reporter assays carried out in one melanoma cell line for DPH3 and OXNAD1 orientations showed statistically significant increased promoter activity due to -8/-9CC > TT tandem mutations; although, no effect of the mutations on DPH3 and OXNAD1 transcription in tumors was observed. The results from this study show occurrence of frequent somatic non-coding mutations adjacent to a pre-existing binding site for Ets transcription factors within the directional promoter of DPH3 and OXNAD1 genes in three major skin cancers. The detected mutations displayed typical UV signature; however, the functionality of the mutations remains to be determined.
Collapse
Affiliation(s)
- Evgeniya Denisova
- Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany
| | - Barbara Heidenreich
- Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany
| | - Eduardo Nagore
- Department of Dermatology, Instituto Valenciano de Oncologia, Valencia, Spain
| | | | - Ismail Hosen
- Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany
| | - Ivana Akrap
- Interfaculty Institute of Cell Biology, Tuebingen University, and IMPRS ("From Molecules to Organisms"), Tuebingen, Germany
| | - Víctor Traves
- Department of Pathology, Instituto Valenciano de Oncologia, Valencia, Spain
| | - Zaida García-Casado
- Laboratory of Molecular Biology, Instituto Valenciano de Oncologia, Valencia, Spain
| | | | - Celia Requena
- Department of Dermatology, Instituto Valenciano de Oncologia, Valencia, Spain
| | - Onofre Sanmartin
- Department of Dermatology, Instituto Valenciano de Oncologia, Valencia, Spain
| | | | - Beatriz Llombart
- Department of Dermatology, Instituto Valenciano de Oncologia, Valencia, Spain
| | - Carlos Guillén
- Department of Dermatology, Instituto Valenciano de Oncologia, Valencia, Spain
| | - Jose Ferrando
- Departments of Pathology & Dermatology, Hospital Arnau de Vilanova, Valencia, Spain
| | - Enrique Gimeno
- Departments of Pathology & Dermatology, Hospital Arnau de Vilanova, Valencia, Spain
| | - Alfred Nordheim
- Interfaculty Institute of Cell Biology, Tuebingen University, and IMPRS ("From Molecules to Organisms"), Tuebingen, Germany.,German Cancer Consortium (DKTK/DKFZ), Heidelberg, Germany
| | - Kari Hemminki
- Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany.,Center for Primary Health Care Research, Lund University, Malmö, Sweden
| | - Rajiv Kumar
- Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany
| |
Collapse
|
14
|
Billod JM, Saenz-Mendez P, Blomberg A, Eriksson LA. Structures, Properties, and Dynamics of Intermediates in eEF2-Diphthamide Biosynthesis. J Chem Inf Model 2016; 56:1776-86. [PMID: 27525663 DOI: 10.1021/acs.jcim.6b00223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The eukaryotic translation Elongation Factor 2 (eEF2) is an essential enzyme in protein synthesis. eEF2 contains a unique modification of a histidine (His699 in yeast; HIS) into diphthamide (DTA), obtained via 3-amino-3-carboxypropyl (ACP) and diphthine (DTI) intermediates in the biosynthetic pathway. This essential and unique modification is also vulnerable, in that it can be efficiently targeted by NAD(+)-dependent ADP-ribosylase toxins, such as diphtheria toxin (DT). However, none of the intermediates in the biosynthesis path is equally vulnerable against the toxins. This study aims to address the different susceptibility of DTA and its precursors against bacterial toxins. We have herein undertaken a detailed in silico study of the structural features and dynamic motion of different His699 intermediates along the diphthamide synthesis pathway (HIS, ACP, DTI, DTA). The study points out that DTA forms a strong hydrogen bond with an asparagine which might explain the ADP-ribosylation mechanism caused by the diphtheria toxin (DT). Finally, in silico mutagenesis studies were performed on the DTA modified protein, in order to hamper the formation of such a hydrogen bond. The results indicate that the mutant structure might in fact be less susceptible to attack by DT and thereby behave similarly to DTI in this respect.
Collapse
Affiliation(s)
- Jean-Marc Billod
- Department of Chemical and Physical Biology, Center for Biological Research, CIB-CSIC , 28040 Madrid, Spain
| | - Patricia Saenz-Mendez
- Computational Chemistry and Biology Group, Facultad de Química, Universidad de la República , 11800 Montevideo, Uruguay
| | | | | |
Collapse
|
15
|
Michalska M, Wolf P. Pseudomonas Exotoxin A: optimized by evolution for effective killing. Front Microbiol 2015; 6:963. [PMID: 26441897 PMCID: PMC4584936 DOI: 10.3389/fmicb.2015.00963] [Citation(s) in RCA: 160] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 08/31/2015] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas Exotoxin A (PE) is the most toxic virulence factor of the pathogenic bacterium Pseudomonas aeruginosa. This review describes current knowledge about the intoxication pathways of PE. Moreover, PE represents a remarkable example for pathoadaptive evolution, how bacterial molecules have been structurally and functionally optimized under evolutionary pressure to effectively impair and kill their host cells.
Collapse
Affiliation(s)
- Marta Michalska
- Department of Urology, Medical Center, University of Freiburg Freiburg, Germany
| | - Philipp Wolf
- Department of Urology, Medical Center, University of Freiburg Freiburg, Germany
| |
Collapse
|
16
|
Whole-genome RNAi screen highlights components of the endoplasmic reticulum/Golgi as a source of resistance to immunotoxin-mediated cytotoxicity. Proc Natl Acad Sci U S A 2015; 112:E1135-42. [PMID: 25713356 DOI: 10.1073/pnas.1501958112] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Immunotoxins (antibody-toxin fusion proteins) target surface antigens on cancer cells and kill these cells via toxin-mediated inhibition of protein synthesis. To identify genes controlling this process, an RNAi whole-genome screen (∼ 22,000 genes at three siRNAs per gene) was conducted via monitoring the cytotoxicity of the mesothelin-directed immunotoxin SS1P. SS1P, a Pseudomonas exotoxin-based immunotoxin, was chosen because it is now in clinical trials and has produced objective tumor regressions in patients. High and low concentrations of SS1P were chosen to allow for the identification of both mitigators and sensitizers. As expected, silencing known essential genes in the immunotoxin pathway, such as mesothelin, furin, KDEL receptor 2, or members of the diphthamide pathway, protected cells. Of greater interest was the observation that many RNAi targets increased immunotoxin sensitivity, indicating that these gene products normally contribute to inefficiencies in the killing pathway. Of the top sensitizers, many genes encode proteins that locate to either the endoplasmic reticulum (ER) or Golgi and are annotated as part of the secretory system. Genes related to the ER-associated degradation system were not among high-ranking mitigator or sensitizer candidates. However, the p97 inhibitor eeyarestatin 1 enhanced immunotoxin killing. Our results highlight potential targets for chemical intervention that could increase immunotoxin killing of cancer cells and enhance our understanding of toxin trafficking.
Collapse
|
17
|
Glatt S, Zabel R, Vonkova I, Kumar A, Netz DJ, Pierik AJ, Rybin V, Lill R, Gavin AC, Balbach J, Breunig KD, Müller CW. Structure of the Kti11/Kti13 heterodimer and its double role in modifications of tRNA and eukaryotic elongation factor 2. Structure 2014; 23:149-160. [PMID: 25543256 DOI: 10.1016/j.str.2014.11.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 11/11/2014] [Accepted: 11/13/2014] [Indexed: 12/14/2022]
Abstract
The small, highly conserved Kti11 alias Dph3 protein encoded by the Kluyveromyces lactis killer toxin insensitive gene KTI11/DPH3 is involved in the diphthamide modification of eukaryotic elongation factor 2 and, together with Kti13, in Elongator-dependent tRNA wobble base modifications, thereby affecting the speed and accuracy of protein biosynthesis through two distinct mechanisms. We have solved the crystal structures of Saccharomyces cerevisiae Kti13 and the Kti11/Kti13 heterodimer at 2.4 and 2.9 Å resolution, respectively, and validated interacting residues through mutational analysis in vitro and in vivo. We show that metal coordination by Kti11 and its heterodimerization with Kti13 are essential for both translational control mechanisms. Our structural and functional analyses identify Kti13 as an additional component of the diphthamide modification pathway and provide insight into the molecular mechanisms that allow the Kti11/Kti13 heterodimer to coregulate two consecutive steps in ribosomal protein synthesis.
Collapse
Affiliation(s)
- Sebastian Glatt
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Rene Zabel
- Martin-Luther-Universität Halle-Wittenberg, Institut für Biologie, Weinbergweg 10, 06120 Halle (Saale), Germany
| | - Ivana Vonkova
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Amit Kumar
- Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, Betty-Heimann-Straße 7, 06120 Halle (Saale), Germany
| | - Daili J Netz
- Institut für Zytobiologie, Philipps-Universität Marburg, Robert-Koch-Straße 6, 35037 Marburg, Germany
| | - Antonio J Pierik
- Institut für Zytobiologie, Philipps-Universität Marburg, Robert-Koch-Straße 6, 35037 Marburg, Germany
| | - Vladimir Rybin
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Roland Lill
- Institut für Zytobiologie, Philipps-Universität Marburg, Robert-Koch-Straße 6, 35037 Marburg, Germany; LOEWE Zentrum für Synthetische Mikrobiologie SynMikro, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - Anne-Claude Gavin
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Jochen Balbach
- Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, Betty-Heimann-Straße 7, 06120 Halle (Saale), Germany
| | - Karin D Breunig
- Martin-Luther-Universität Halle-Wittenberg, Institut für Biologie, Weinbergweg 10, 06120 Halle (Saale), Germany.
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany.
| |
Collapse
|
18
|
Schaffrath R, Abdel-Fattah W, Klassen R, Stark MJR. The diphthamide modification pathway from Saccharomyces cerevisiae--revisited. Mol Microbiol 2014; 94:1213-26. [PMID: 25352115 DOI: 10.1111/mmi.12845] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2014] [Indexed: 01/09/2023]
Abstract
Diphthamide is a conserved modification in archaeal and eukaryal translation elongation factor 2 (EF2). Its name refers to the target function for diphtheria toxin, the disease-causing agent that, through ADP ribosylation of diphthamide, causes irreversible inactivation of EF2 and cell death. Although this clearly emphasizes a pathobiological role for diphthamide, its physiological function is unclear, and precisely why cells need EF2 to contain diphthamide is hardly understood. Nonetheless, the conservation of diphthamide biosynthesis together with syndromes (i.e. ribosomal frame-shifting, embryonic lethality, neurodegeneration and cancer) typical of mutant cells that cannot make it strongly suggests that diphthamide-modified EF2 occupies an important and translation-related role in cell proliferation and development. Whether this is structural and/or regulatory remains to be seen. However, recent progress in dissecting the diphthamide gene network (DPH1-DPH7) from the budding yeast Saccharomyces cerevisiae has significantly advanced our understanding of the mechanisms required to initiate and complete diphthamide synthesis on EF2. Here, we review recent developments in the field that not only have provided novel, previously overlooked and unexpected insights into the pathway and the biochemical players required for diphthamide synthesis but also are likely to foster innovative studies into the potential regulation of diphthamide, and importantly, its ill-defined biological role.
Collapse
Affiliation(s)
- Raffael Schaffrath
- Department of Genetics, University of Leicester, Leicester, LE1 7RH, UK; Institut für Biologie, Abteilung Mikrobiologie, Universität Kassel, 34132, Kassel, Germany
| | | | | | | |
Collapse
|
19
|
Dong M, Su X, Dzikovski B, Dando EE, Zhu X, Du J, Freed JH, Lin H. Dph3 is an electron donor for Dph1-Dph2 in the first step of eukaryotic diphthamide biosynthesis. J Am Chem Soc 2014; 136:1754-7. [PMID: 24422557 PMCID: PMC3985478 DOI: 10.1021/ja4118957] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Diphthamide, the target of diphtheria toxin, is a unique posttranslational modification on translation elongation factor 2 (EF2) in archaea and eukaryotes. The biosynthesis of diphthamide was proposed to involve three steps. The first step is the transfer of the 3-amino-3-carboxypropyl group from S-adenosyl-l-methionine (SAM) to the histidine residue of EF2, forming a C-C bond. Previous genetic studies showed this step requires four proteins in eukaryotes, Dph1-Dph4. However, the exact molecular functions for the four proteins are unknown. Previous study showed that Pyrococcus horikoshii Dph2 (PhDph2), a novel iron-sulfur cluster-containing enzyme, forms a homodimer and is sufficient for the first step of diphthamide biosynthesis in vitro. Here we demonstrate by in vitro reconstitution that yeast Dph1 and Dph2 form a complex (Dph1-Dph2) that is equivalent to the homodimer of PhDph2 and is sufficient to catalyze the first step in vitro in the presence of dithionite as the reductant. We further demonstrate that yeast Dph3 (also known as KTI11), a CSL-type zinc finger protein, can bind iron and in the reduced state can serve as an electron donor to reduce the Fe-S cluster in Dph1-Dph2. Our study thus firmly establishes the functions for three of the proteins involved in eukaryotic diphthamide biosynthesis. For most radical SAM enzymes in bacteria, flavodoxins and flavodoxin reductases are believed to serve as electron donors for the Fe-S clusters. The finding that Dph3 is an electron donor for the Fe-S clusters in Dph1-Dph2 is thus interesting and opens up new avenues of research on electron transfer to Fe-S proteins in eukaryotic cells.
Collapse
Affiliation(s)
- Min Dong
- Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Abstract
Eukaryotic and archaeal elongation factor 2 contains a unique post-translationally modified histidine residue, named diphthamide. Genetic and biochemical studies have revealed that diphthamide biosynthesis involves a multi-step pathway that is evolutionally conserved among lower and higher eukaryotes. During certain bacterial infections, diphthamide is specifically recognized by bacterial toxins, including diphtheria toxin, Pseudomonas exotoxin A and cholix toxin. Although the pathological relevance is well studied, the physiological function of diphthamide is still poorly understood. Recently, many new interesting developments in understanding the biosynthesis have been reported. Here, we review the current understanding of the biosynthesis and biological function of diphthamide.
Collapse
Affiliation(s)
- Xiaoyang Su
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850, USA
| | - Zhewang Lin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850, USA
| | - Hening Lin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850, USA
| |
Collapse
|