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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.
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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;
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Chen Y, Yang B, Zhang XM, Chen S, Wang M, Hu L, Pan N, Li S, Shi W, Yang Z, Wang L, Tan Y, Wang J, Wang Y, Xing Q, Ma Z, Li J, Huang HF, Zhang J, Xu C. Biallelic variants in RBM42 cause a multisystem disorder with neurological, facial, cardiac, and musculoskeletal involvement. Protein Cell 2024; 15:52-68. [PMID: 37294900 PMCID: PMC10762670 DOI: 10.1093/procel/pwad034] [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: 12/28/2022] [Accepted: 04/29/2023] [Indexed: 06/11/2023] Open
Abstract
Here, we report a previously unrecognized syndromic neurodevelopmental disorder associated with biallelic loss-of-function variants in the RBM42 gene. The patient is a 2-year-old female with severe central nervous system (CNS) abnormalities, hypotonia, hearing loss, congenital heart defects, and dysmorphic facial features. Familial whole-exome sequencing (WES) reveals that the patient has two compound heterozygous variants, c.304C>T (p.R102*) and c.1312G>A (p.A438T), in the RBM42 gene which encodes an integral component of splicing complex in the RNA-binding motif protein family. The p.A438T variant is in the RRM domain which impairs RBM42 protein stability in vivo. Additionally, p.A438T disrupts the interaction of RBM42 with hnRNP K, which is the causative gene for Au-Kline syndrome with overlapping disease characteristics seen in the index patient. The human R102* or A438T mutant protein failed to fully rescue the growth defects of RBM42 ortholog knockout ΔFgRbp1 in Fusarium while it was rescued by the wild-type (WT) human RBM42. A mouse model carrying Rbm42 compound heterozygous variants, c.280C>T (p.Q94*) and c.1306_1308delinsACA (p.A436T), demonstrated gross fetal developmental defects and most of the double mutant animals died by E13.5. RNA-seq data confirmed that Rbm42 was involved in neurological and myocardial functions with an essential role in alternative splicing (AS). Overall, we present clinical, genetic, and functional data to demonstrate that defects in RBM42 constitute the underlying etiology of a new neurodevelopmental disease which links the dysregulation of global AS to abnormal embryonic development.
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Affiliation(s)
- Yiyao Chen
- Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Bingxin Yang
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Xiaoyu Merlin Zhang
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Songchang Chen
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai 200011, China
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
| | - Minhui Wang
- State Key Laboratory of Rice Biology, the Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Liya Hu
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Nina Pan
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
| | - Shuyuan Li
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Weihui Shi
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai 200011, China
| | - Zhenhua Yang
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
- School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, Zhejiang, China
| | - Li Wang
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Yajing Tan
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Jian Wang
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Yanlin Wang
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Qinghe Xing
- Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
- Children’s hospital of Fudan University, Shanghai 201102, China
| | - Zhonghua Ma
- State Key Laboratory of Rice Biology, the Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai 201210, China
- School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, Zhejiang, China
| | - He-Feng Huang
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai 200011, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
- Research Units of Embryo Original Diseases, Chinese Academy of Medical Sciences (No. 2019RU056), Shanghai 200011, China
| | - Jinglan Zhang
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai 200011, China
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
- Shanghai Key Laboratory of Embryo Original Diseases, Shanghai 200030, China
| | - Chenming Xu
- Obstetrics and Gynecology Hospital, Institute of Reproduction and Development, Fudan University, Shanghai 200011, China
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
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Milicevic N, Jenner L, Myasnikov A, Yusupov M, Yusupova G. mRNA reading frame maintenance during eukaryotic ribosome translocation. Nature 2024; 625:393-400. [PMID: 38030725 DOI: 10.1038/s41586-023-06780-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 10/24/2023] [Indexed: 12/01/2023]
Abstract
One of the most critical steps of protein synthesis is coupled translocation of messenger RNA (mRNA) and transfer RNAs (tRNAs) required to advance the mRNA reading frame by one codon. In eukaryotes, translocation is accelerated and its fidelity is maintained by elongation factor 2 (eEF2)1,2. At present, only a few snapshots of eukaryotic ribosome translocation have been reported3-5. Here we report ten high-resolution cryogenic-electron microscopy (cryo-EM) structures of the elongating eukaryotic ribosome bound to the full translocation module consisting of mRNA, peptidyl-tRNA and deacylated tRNA, seven of which also contained ribosome-bound, naturally modified eEF2. This study recapitulates mRNA-tRNA2-growing peptide module progression through the ribosome, from the earliest states of eEF2 translocase accommodation until the very late stages of the process, and shows an intricate network of interactions preventing the slippage of the translational reading frame. We demonstrate how the accuracy of eukaryotic translocation relies on eukaryote-specific elements of the 80S ribosome, eEF2 and tRNAs. Our findings shed light on the mechanism of translation arrest by the anti-fungal eEF2-binding inhibitor, sordarin. We also propose that the sterically constrained environment imposed by diphthamide, a conserved eukaryotic posttranslational modification in eEF2, not only stabilizes correct Watson-Crick codon-anticodon interactions but may also uncover erroneous peptidyl-tRNA, and therefore contribute to higher accuracy of protein synthesis in eukaryotes.
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Affiliation(s)
- Nemanja Milicevic
- Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR7104, INSERM U1258, University of Strasbourg, Strasbourg, France
| | - Lasse Jenner
- Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR7104, INSERM U1258, University of Strasbourg, Strasbourg, France
| | | | - Marat Yusupov
- Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR7104, INSERM U1258, University of Strasbourg, Strasbourg, France
| | - Gulnara Yusupova
- Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR7104, INSERM U1258, University of Strasbourg, Strasbourg, France.
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Ütkür K, Schmidt S, Mayer K, Klassen R, Brinkmann U, Schaffrath R. DPH1 Gene Mutations Identify a Candidate SAM Pocket in Radical Enzyme Dph1•Dph2 for Diphthamide Synthesis on EF2. Biomolecules 2023; 13:1655. [PMID: 38002337 PMCID: PMC10669111 DOI: 10.3390/biom13111655] [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: 10/24/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
In eukaryotes, the Dph1•Dph2 dimer is a non-canonical radical SAM enzyme. Using iron-sulfur (FeS) clusters, it cleaves the cosubstrate S-adenosyl-methionine (SAM) to form a 3-amino-3-carboxy-propyl (ACP) radical for the synthesis of diphthamide. The latter decorates a histidine residue on elongation factor 2 (EF2) conserved from archaea to yeast and humans and is important for accurate mRNA translation and protein synthesis. Guided by evidence from archaeal orthologues, we searched for a putative SAM-binding pocket in Dph1•Dph2 from Saccharomyces cerevisiae. We predict an SAM-binding pocket near the FeS cluster domain that is conserved across eukaryotes in Dph1 but not Dph2. Site-directed DPH1 mutagenesis and functional characterization through assay diagnostics for the loss of diphthamide reveal that the SAM pocket is essential for synthesis of the décor on EF2 in vivo. Further evidence from structural modeling suggests particularly critical residues close to the methionine moiety of SAM. Presumably, they facilitate a geometry specific for SAM cleavage and ACP radical formation that distinguishes Dph1•Dph2 from classical radical SAM enzymes, which generate canonical 5'-deoxyadenosyl (dAdo) radicals.
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Affiliation(s)
- Koray Ütkür
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany; (K.Ü.); (S.S.); (R.K.)
| | - Sarina Schmidt
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany; (K.Ü.); (S.S.); (R.K.)
| | - Klaus Mayer
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, 82377 Penzberg, Germany; (K.M.); (U.B.)
| | - Roland Klassen
- Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany; (K.Ü.); (S.S.); (R.K.)
| | - 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
- Roche Pharma Research and Early Development (pRED), Large Molecule Research, Roche Innovation Center Munich, 82377 Penzberg, Germany; (K.M.); (U.B.)
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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: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [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.
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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
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