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Bolgi O, Silva-Garcia M, Ross B, Pilla E, Kari V, Killisch M, Spitzner M, Stark N, Lenz C, Weiss K, Donzelli L, Gorrell MD, Grade M, Riemer J, Urlaub H, Dobbelstein M, Huber R, Geiss-Friedlander R. Dipeptidyl peptidase 9 triggers BRCA2 degradation and promotes DNA damage repair. EMBO Rep 2022; 23:e54136. [PMID: 35912982 PMCID: PMC9535758 DOI: 10.15252/embr.202154136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 07/01/2022] [Accepted: 07/07/2022] [Indexed: 12/30/2022] Open
Abstract
N-terminal sequences are important sites for post-translational modifications that alter protein localization, activity, and stability. Dipeptidyl peptidase 9 (DPP9) is a serine aminopeptidase with the rare ability to cleave off N-terminal dipeptides with imino acid proline in the second position. Here, we identify the tumor-suppressor BRCA2 as a DPP9 substrate and show this interaction to be induced by DNA damage. We present crystallographic structures documenting intracrystalline enzymatic activity of DPP9, with the N-terminal Met1-Pro2 of a BRCA21-40 peptide captured in its active site. Intriguingly, DPP9-depleted cells are hypersensitive to genotoxic agents and are impaired in the repair of DNA double-strand breaks by homologous recombination. Mechanistically, DPP9 targets BRCA2 for degradation and promotes the formation of RAD51 foci, the downstream function of BRCA2. N-terminal truncation mutants of BRCA2 that mimic a DPP9 product phenocopy reduced BRCA2 stability and rescue RAD51 foci formation in DPP9-deficient cells. Taken together, we present DPP9 as a regulator of BRCA2 stability and propose that by fine-tuning the cellular concentrations of BRCA2, DPP9 alters the BRCA2 interactome, providing a possible explanation for DPP9's role in cancer.
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Affiliation(s)
- Oguz Bolgi
- Institute of Molecular Medicine and Cell Research, Medical Faculty, University of Freiburg, Freiburg, Germany.,Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Maria Silva-Garcia
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Breyan Ross
- Max Planck Institut für Biochemie, Martinsried, Germany.,Proteros Biostructures GmbH, Martinsried, Germany
| | - Esther Pilla
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Vijayalakshmi Kari
- Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, Göttingen, Germany
| | - Markus Killisch
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Melanie Spitzner
- Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, Göttingen, Germany
| | - Nadine Stark
- Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen, Germany
| | - Christof Lenz
- Bioanalytics, Institute of Clinical Chemistry, University Medical Center, Göttingen, Germany.,Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Konstantin Weiss
- Institute of Biochemistry, Redox Biochemistry, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Laura Donzelli
- Institute of Molecular Medicine and Cell Research, Medical Faculty, University of Freiburg, Freiburg, Germany
| | - Mark D Gorrell
- Centenary Institute, The University of Sydney Faculty of Medicine and Health, Sydney, NSW, Australia
| | - Marian Grade
- Department of General, Visceral and Pediatric Surgery, University Medical Center Göttingen, Göttingen, Germany
| | - Jan Riemer
- Institute of Biochemistry, Redox Biochemistry, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Henning Urlaub
- Bioanalytics, Institute of Clinical Chemistry, University Medical Center, Göttingen, Germany.,Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Matthias Dobbelstein
- Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen, Germany
| | - Robert Huber
- Max Planck Institut für Biochemie, Martinsried, Germany.,Zentrum für Medizinische Biotechnologie, Universität Duisburg-Essen, Essen, Germany.,Fakultät für Chemie, Technische Universität München, Garching, Germany
| | - Ruth Geiss-Friedlander
- Institute of Molecular Medicine and Cell Research, Medical Faculty, University of Freiburg, Freiburg, Germany.,Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
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2
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Muhamad Ismail NAS, Yap SH, Mohamad Yussoff MA, Nor Muhammad NA, Firdaus-Raih M, Quay DHX. Modeling and computational characterization of a Xanthomonas sp. Hypothetical protein identifies a remote ortholog of Burkholderia lethal factor 1. J Biomol Struct Dyn 2022:1-13. [PMID: 35862639 DOI: 10.1080/07391102.2022.2100827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Burkholderia Lethal Factor 1 (BLF1) is a deamidase first characterized in Burkholderia pseudomallei. This enzyme inhibits cellular protein synthesis by deamidating a glutamine residue to a glutamic acid in its target protein, the eukaryotic translation initiation factor 4 A (eIF4A). In this work, we present the characterization of a hypothetical protein from Xanthomonas sp. Leaf131 as the first report of a BLF1 family ortholog outside of the Burkholderia genus. Although standard sequence similarity searches such as BLAST were not able to detect the homology between the Xanthomonas sp. Leaf131 hypothetical protein sequence and BLF1, our computed structure model for the Xanthomonas sp. hypothetical protein revealed structural similarities with an RMSD of 2.7 Å/164 Cα atoms and a TM-score of 0.72 when superposed. Structural comparisons of the Xanthomonas model structure against BLF1 and Escherichia coli cytotoxic necrotizing factor 1 (CNF1) revealed that the conserved signature LXGC motif and putative catalytic residues are structurally aligned thus signifying a level of functional or mechanistic similarity. Protein-protein docking analysis and molecular dynamics simulations also demonstrated that eIF4A could still be a possible target substrate for deamidation by XLF1 as it is for BLF1. We therefore propose that this Xanthomonas hypothetical protein be renamed as Xanthomonas Lethal Factor 1 (XLF1). Our work also provides further evidence of the utility of programs such as AlphaFold in bridging the computational function annotation transfer gap despite very low sequence identities of under 20%.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
| | - Su Hui Yap
- Bioinformatics Programme, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
| | | | - Nor Azlan Nor Muhammad
- Institute of Systems Biology, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia
| | - Mohd Firdaus-Raih
- Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia.,Bioinformatics Programme, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia.,Institute of Systems Biology, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia
| | - Doris Huai Xia Quay
- Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia.,Bioinformatics Programme, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
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3
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Mobbs GW, Aziz AA, Dix SR, Blackburn GM, Sedelnikova SE, Minshull TC, Dickman MJ, Baker PJ, Nathan S, Raih MF, Rice DW. Molecular basis of specificity and deamidation of eIF4A by Burkholderia Lethal Factor 1. Commun Biol 2022; 5:272. [PMID: 35347220 PMCID: PMC8960835 DOI: 10.1038/s42003-022-03186-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 02/17/2022] [Indexed: 12/22/2022] Open
Abstract
Burkholderiapseudomallei lethal factor 1 (BLF1) exhibits site-specific glutamine deamidase activity against the eukaryotic RNA helicase, eIF4A, thereby blocking mammalian protein synthesis. The structure of a complex between BLF1 C94S and human eIF4A shows that the toxin binds in the cleft between the two RecA-like eIF4A domains forming interactions with residues from both and with the scissile amide of the target glutamine, Gln339, adjacent to the toxin active site. The RecA-like domains adopt a radically twisted orientation compared to other eIF4A structures and the nature and position of conserved residues suggests this may represent a conformation associated with RNA binding. Comparison of the catalytic site of BLF1 with other deamidases and cysteine proteases reveals that they fall into two classes, related by pseudosymmetry, that present either the re or si faces of the target amide/peptide to the nucleophilic sulfur, highlighting constraints in the convergent evolution of their Cys-His active sites. The crystal structure of the toxin from the pathogenic bacterium Burkholderia pseudomallei in complex with its target, human eIF4A, provides insights into substrate specificity and may facilitate the design of inhibitors for the treatment of melioidosis.
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Tying up loose ends: the N-degron and C-degron pathways of protein degradation. Biochem Soc Trans 2021; 48:1557-1567. [PMID: 32627813 PMCID: PMC7458402 DOI: 10.1042/bst20191094] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/11/2020] [Accepted: 06/15/2020] [Indexed: 12/13/2022]
Abstract
Selective protein degradation by the ubiquitin-proteasome system (UPS) is thought to be governed primarily by the recognition of specific motifs — degrons — present in substrate proteins. The ends of proteins — the N- and C-termini – have unique properties, and an important subset of protein–protein interactions involve the recognition of free termini. The first degrons to be discovered were located at the extreme N-terminus of proteins, a finding which initiated the study of the N-degron (formerly N-end rule) pathways, but only in the last few years has it emerged that a diverse set of C-degron pathways target analogous degron motifs located at the extreme C-terminus of proteins. In this minireview we summarise the N-degron and C-degron pathways currently known to operate in human cells, focussing primarily on those that have been discovered in recent years. In each case we describe the cellular machinery responsible for terminal degron recognition, and then consider some of the functional roles of terminal degron pathways. Altogether, a broad spectrum of E3 ubiquitin ligases mediate the recognition of a diverse array of terminal degron motifs; these degradative pathways have the potential to influence a wide variety of cellular functions.
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5
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The Arg/N-degron pathway targets transcription factors and regulates specific genes. Proc Natl Acad Sci U S A 2020; 117:31094-31104. [PMID: 33229537 DOI: 10.1073/pnas.2020124117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The Arg/N-degron pathway targets proteins for degradation by recognizing their N-terminal or internal degrons. Our previous work produced double-knockout (2-KO) HEK293T human cell lines that lacked the functionally overlapping UBR1 and UBR2 E3 ubiquitin ligases of the Arg/N-degron pathway. Here, we studied these cells in conjunction with RNA-sequencing, mass spectrometry (MS), and split-ubiquitin binding assays. 1) Some mRNAs, such as those encoding lactate transporter MCT2 and β-adrenergic receptor ADRB2, are strongly (∼20-fold) up-regulated in 2-KO cells, whereas other mRNAs, including those encoding MAGEA6 (a regulator of ubiquitin ligases) and LCP1 (an actin-binding protein), are completely repressed in 2-KO cells, in contrast to wild-type cells. 2) Glucocorticoid receptor (GR), an immunity-modulating transcription factor (TF), is up-regulated in 2-KO cells and also physically binds to UBR1, strongly suggesting that GR is a physiological substrate of the Arg/N-degron pathway. 3) PREP1, another TF, was also found to bind to UBR1. 4) MS-based analyses identified ∼160 proteins whose levels were increased or decreased by more than 2-fold in 2-KO cells. For example, the homeodomain TF DACH1 and the neurofilament subunits NF-L (NFEL) and NF-M (NFEM) were expressed in wild-type cells but were virtually absent in 2-KO cells. 5) The disappearance of some proteins in 2-KO cells took place despite up-regulation of their mRNAs, strongly suggesting that the Arg/N-degron pathway can also modulate translation of specific mRNAs. In sum, this multifunctional proteolytic system has emerged as a regulator of mammalian gene expression, in part through conditional targeting of TFs that include ATF3, GR, and PREP1.
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6
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Vu TTM, Varshavsky A. The ATF3 Transcription Factor Is a Short-Lived Substrate of the Arg/N-Degron Pathway. Biochemistry 2020; 59:2796-2812. [PMID: 32692156 DOI: 10.1021/acs.biochem.0c00514] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The Arg/N-degron pathway targets proteins for degradation by recognizing their specific N-terminal residues or, alternatively, their non-N-terminal degrons. In mammals, this pathway is mediated by the UBR1, UBR2, UBR4, and UBR5 E3 ubiquitin ligases, and by the p62 regulator of autophagy. UBR1 and UBR2 are sequelogous, functionally overlapping, and dominate the targeting of Arg/N-degron substrates in examined cell lines. We constructed, here, mouse strains in which the double mutant [UBR1-/- UBR2-/-] genotype can be induced conditionally, in adult mice. We also constructed human [UBR1-/- UBR2-/-] HEK293T cell lines that unconditionally lack UBR1/UBR2. ATF3 is a basic leucine zipper transcription factor that regulates hundreds of genes and can act as either a repressor or an activator of transcription. Using the above double-mutant mice and human cells, we found that the levels of endogenous, untagged ATF3 were significantly higher in both of these [UBR1-/- UBR2-/-] settings than in wild-type cells. We also show, through chase-degradation assays with [UBR1-/- UBR2-/-] and wild-type human cells, that the Arg/N-degron pathway mediates a large fraction of ATF3 degradation. Furthermore, we used split-ubiquitin and another protein interaction assay to detect the binding of ATF3 to both UBR1 and UBR2, in agreement with the UBR1/UBR2-mediated degradation of endogenous ATF3. Full-length 24 kDa ATF3 binds to ∼100 kDa fragments of 200 kDa UBR1 and UBR2 but does not bind (in the setting of interaction assays) to full-length UBR1/UBR2. These and other binding patterns, whose mechanics remain to be understood, may signify a conditional (regulated) degradation of ATF3 by the Arg/N-degron pathway.
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Affiliation(s)
- Tri T M Vu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Alexander Varshavsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
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Enríquez-Flores S, Flores-López LA, García-Torres I, de la Mora-de la Mora I, Cabrera N, Gutiérrez-Castrellón P, Martínez-Pérez Y, López-Velázquez G. Deamidated Human Triosephosphate Isomerase is a Promising Druggable Target. Biomolecules 2020; 10:E1050. [PMID: 32679775 PMCID: PMC7407242 DOI: 10.3390/biom10071050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 07/04/2020] [Accepted: 07/10/2020] [Indexed: 12/27/2022] Open
Abstract
Therapeutic strategies for the treatment of any severe disease are based on the discovery and validation of druggable targets. The human genome encodes only 600-1500 targets for small-molecule drugs, but posttranslational modifications lead to a considerably larger druggable proteome. The spontaneous conversion of asparagine (Asn) residues to aspartic acid or isoaspartic acid is a frequent modification in proteins as part of the process called deamidation. Triosephosphate isomerase (TIM) is a glycolytic enzyme whose deamidation has been thoroughly studied, but the prospects of exploiting this phenomenon for drug design remain poorly understood. The purpose of this study is to demonstrate the properties of deamidated human TIM (HsTIM) as a selective molecular target. Using in silico prediction, in vitro analyses, and a bacterial model lacking the tim gene, this study analyzed the structural and functional differences between deamidated and nondeamidated HsTIM, which account for the efficacy of this protein as a druggable target. The highly increased permeability and loss of noncovalent interactions of deamidated TIM were found to play a central role in the process of selective enzyme inactivation and methylglyoxal production. This study elucidates the properties of deamidated HsTIM regarding its selective inhibition by thiol-reactive drugs and how these drugs can contribute to the development of cell-specific therapeutic strategies for a variety of diseases, such as COVID-19 and cancer.
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Affiliation(s)
- Sergio Enríquez-Flores
- Grupo de Investigación en Biomoléculas y Salud Infantil, Laboratorio de EIMyT, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.A.F.-L.); (I.G.-T.); (I.d.l.M.-d.l.M.)
| | - Luis Antonio Flores-López
- Grupo de Investigación en Biomoléculas y Salud Infantil, Laboratorio de EIMyT, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.A.F.-L.); (I.G.-T.); (I.d.l.M.-d.l.M.)
- CONACYT-Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
| | - Itzhel García-Torres
- Grupo de Investigación en Biomoléculas y Salud Infantil, Laboratorio de EIMyT, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.A.F.-L.); (I.G.-T.); (I.d.l.M.-d.l.M.)
| | - Ignacio de la Mora-de la Mora
- Grupo de Investigación en Biomoléculas y Salud Infantil, Laboratorio de EIMyT, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.A.F.-L.); (I.G.-T.); (I.d.l.M.-d.l.M.)
| | - Nallely Cabrera
- Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
| | | | - Yoalli Martínez-Pérez
- Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
| | - Gabriel López-Velázquez
- Grupo de Investigación en Biomoléculas y Salud Infantil, Laboratorio de EIMyT, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.A.F.-L.); (I.G.-T.); (I.d.l.M.-d.l.M.)
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8
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Wu Z, Liu C, Zhang Z, Zheng R, Zheng Y. Amidase as a versatile tool in amide-bond cleavage: From molecular features to biotechnological applications. Biotechnol Adv 2020; 43:107574. [PMID: 32512219 DOI: 10.1016/j.biotechadv.2020.107574] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 05/31/2020] [Accepted: 06/01/2020] [Indexed: 12/27/2022]
Abstract
Amidases (EC 3. 5. 1. X) are versatile biocatalysts for synthesis of chiral carboxylic acids, α-amino acids and amides due to their hydrolytic and acyl transfer activity towards the C-N linkages. They have been extensively exploited and studied during the past years for their high specific activity and excellent enantioselectivity involved in various biotechnological applications in pharmaceutical and agrochemical industries. Additionally, they have attracted considerable attentions in biodegradation and bioremediation owing to environmental pressures. Motivated by industrial demands, crystallographic investigations and catalytic mechanisms of amidases based on structural biology have witnessed a dramatic promotion in the last two decades. The protein structures showed that different types of amidases have their typical stuctural elements, such as the conserved AS domains in signature amidases and the typical architecture of metal-associated active sites in acetamidase/formamidase family amidases. This review provides an overview of recent research advances in various amidases, with a focus on their structural basis of phylogenetics, substrate specificities and catalytic mechanisms as well as their biotechnological applications. As more crystal structures of amidases are determined, the structure/function relationships of these enzymes will also be further elucidated, which will facilitate molecular engineering and design of amidases to meet industrial requirements.
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Affiliation(s)
- Zheming Wu
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; Engineering Research Center of Bioconversion and Biopurification of Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
| | - Changfeng Liu
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; Engineering Research Center of Bioconversion and Biopurification of Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
| | - Zhaoyu Zhang
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; Engineering Research Center of Bioconversion and Biopurification of Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
| | - Renchao Zheng
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; Engineering Research Center of Bioconversion and Biopurification of Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China.
| | - Yuguo Zheng
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; Engineering Research Center of Bioconversion and Biopurification of Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China; The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
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Five enzymes of the Arg/N-degron pathway form a targeting complex: The concept of superchanneling. Proc Natl Acad Sci U S A 2020; 117:10778-10788. [PMID: 32366662 DOI: 10.1073/pnas.2003043117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Arg/N-degron pathway targets proteins for degradation by recognizing their N-terminal (Nt) residues. If a substrate bears, for example, Nt-Asn, its targeting involves deamidation of Nt-Asn, arginylation of resulting Nt-Asp, binding of resulting (conjugated) Nt-Arg to the UBR1-RAD6 E3-E2 ubiquitin ligase, ligase-mediated synthesis of a substrate-linked polyubiquitin chain, its capture by the proteasome, and substrate's degradation. We discovered that the human Nt-Asn-specific Nt-amidase NTAN1, Nt-Gln-specific Nt-amidase NTAQ1, arginyltransferase ATE1, and the ubiquitin ligase UBR1-UBE2A/B (or UBR2-UBE2A/B) form a complex in which NTAN1 Nt-amidase binds to NTAQ1, ATE1, and UBR1/UBR2. In addition, NTAQ1 Nt-amidase and ATE1 arginyltransferase also bind to UBR1/UBR2. In the yeast Saccharomyces cerevisiae, the Nt-amidase, arginyltransferase, and the double-E3 ubiquitin ligase UBR1-RAD6/UFD4-UBC4/5 are shown to form an analogous targeting complex. These complexes may enable substrate channeling, in which a substrate bearing, for example, Nt-Asn, would be captured by a complex-bound Nt-amidase, followed by sequential Nt modifications of the substrate and its polyubiquitylation at an internal Lys residue without substrate's dissociation into the bulk solution. At least in yeast, the UBR1/UFD4 ubiquitin ligase interacts with the 26S proteasome, suggesting an even larger Arg/N-degron-targeting complex that contains the proteasome as well. In addition, specific features of protein-sized Arg/N-degron substrates, including their partly sequential and partly nonsequential enzymatic modifications, led us to a verifiable concept termed "superchanneling." In superchanneling, the synthesis of a substrate-linked poly-Ub chain can occur not only after a substrate's sequential Nt modifications, but also before them, through a skipping of either some or all of these modifications within a targeting complex.
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