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Sakato-Antoku M, Balsbaugh JL, King SM. N-Terminal Processing and Modification of Ciliary Dyneins. Cells 2023; 12:2492. [PMID: 37887336 PMCID: PMC10605206 DOI: 10.3390/cells12202492] [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: 09/15/2023] [Revised: 10/17/2023] [Accepted: 10/19/2023] [Indexed: 10/28/2023] Open
Abstract
Axonemal dyneins are highly complex microtubule motors that power ciliary motility. These multi-subunit enzymes are assembled at dedicated sites within the cytoplasm. At least nineteen cytosolic factors are specifically needed to generate dynein holoenzymes and/or for their trafficking to the growing cilium. Many proteins are subject to N-terminal processing and acetylation, which can generate degrons subject to the AcN-end rule, alter N-terminal electrostatics, generate new binding interfaces, and affect subunit stoichiometry through targeted degradation. Here, we have used mass spectrometry of cilia samples and electrophoretically purified dynein heavy chains from Chlamydomonas to define their N-terminal processing; we also detail the N-terminal acetylase complexes present in this organism. We identify four classes of dynein heavy chain based on their processing pathways by two distinct acetylases, one of which is dependent on methionine aminopeptidase activity. In addition, we find that one component of both the outer dynein arm intermediate/light chain subcomplex and the docking complex is processed to yield an unmodified Pro residue, which may provide a setpoint to direct the cytosolic stoichiometry of other dynein complex subunits that contain N-terminal degrons. Thus, we identify and describe an additional level of processing and complexity in the pathways leading to axonemal dynein formation in cytoplasm.
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Affiliation(s)
- Miho Sakato-Antoku
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3305, USA;
| | - Jeremy L. Balsbaugh
- Proteomics and Metabolomics Facility, University of Connecticut, 75 North Eagleville Road, Storrs, CT 06269, USA;
| | - Stephen M. King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3305, USA;
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2
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In vitro production of N-degron fused proteins and its application. Methods Enzymol 2023. [PMID: 37532410 DOI: 10.1016/bs.mie.2023.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
The N-degron pathway, first discovered several decades ago by Varshavsky's laboratory, controls the half-life of target proteins depending on their N-terminal residues. In vivo cell biology studies have established the physiological role of the N-degron pathway. However, in vitro studies such as biochemical assays and structural biology studies are relatively limited. The N-degron substrates cannot be obtained via simple protein expression. The N-degron residues are exposed via the proteolytic process from the translated nascent polypeptide chains. Thus, methods for the fusion expression with several cleavable tags and subsequent treatment with specific proteases to design the exposed N-degron signals have been introduced. Recently, we developed a unique fusion technique using microtubule-associated protein 1A/1B light chain 3B (LC3B), a key marker protein of autophagy, to obtain a high yield of the purified target proteins with variable N-terminal residues for various biochemical studies including enzymatic and binding assays, and crystallization of N-degron complex. This chapter describes the protocols that include the vector map designed for producing LC3B fused target proteins, methods for expression and purification of an example protein, p62/SQSMT1, using different N-terminal residues, and methods to obtain the purified ATG4B protease, which is used for processing LC3B tag and exposing the required N-terminal residues of the target protein.
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3
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Crystal structure of the Ate1 arginyl-tRNA-protein transferase and arginylation of N-degron substrates. Proc Natl Acad Sci U S A 2022; 119:e2209597119. [PMID: 35878037 PMCID: PMC9351520 DOI: 10.1073/pnas.2209597119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
N-degron pathways are proteolytic systems that target proteins bearing N-terminal (Nt) degradation signals (degrons) called N-degrons. Nt-Arg of a protein is among Nt-residues that can be recognized as destabilizing ones by the Arg/N-degron pathway. A proteolytic cleavage of a protein can generate Arg at the N terminus of a resulting C-terminal (Ct) fragment either directly or after Nt-arginylation of that Ct-fragment by the Ate1 arginyl-tRNA-protein transferase (R-transferase), which uses Arg-tRNAArg as a cosubstrate. Ate1 can Nt-arginylate Nt-Asp, Nt-Glu, and oxidized Nt-Cys* (Cys-sulfinate or Cys-sulfonate) of proteins or short peptides. Ate1 genes of fungi, animals, and plants have been cloned decades ago, but a three-dimensional structure of Ate1 remained unknown. A detailed mechanism of arginylation is unknown as well. We describe here the crystal structure of the Ate1 R-transferase from the budding yeast Kluyveromyces lactis. The 58-kDa R-transferase comprises two domains that recognize, together, an acidic Nt-residue of an acceptor substrate, the Arg residue of Arg-tRNAArg, and a 3'-proximal segment of the tRNAArg moiety. The enzyme's active site is located, at least in part, between the two domains. In vitro and in vivo arginylation assays with site-directed Ate1 mutants that were suggested by structural results yielded inferences about specific binding sites of Ate1. We also analyzed the inhibition of Nt-arginylation activity of Ate1 by hemin (Fe3+-heme), and found that hemin induced the previously undescribed disulfide-mediated oligomerization of Ate1. Together, these results advance the understanding of R-transferase and the Arg/N-degron pathway.
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4
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Xiong Y, Li M, Lu W, Wang D, Tang M, Liu Y, Na B, Qin H, Qing G. Discerning Tyrosine Phosphorylation from Multiple Phosphorylations Using a Nanofluidic Logic Platform. Anal Chem 2021; 93:16113-16122. [PMID: 34841853 DOI: 10.1021/acs.analchem.1c03889] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Discerning tyrosine phosphorylation (pTyr) catalyzed by Tyr kinase is central to the revelation of oncogenic mechanisms and the development of targeted anticancer drugs. Despite some techniques, this goal remains challenging, especially when faced with the interference of multiple phosphorylation events, including serine (pSer) and threonine phosphorylation (pThr). We describe here a functional polymer-modified artificial ion nanochannel, which enables the sensitive and selective recognition of phosphotyrosine (pY) peptide by the distinct ionic current change. Such a recognition effect allows for the nanochannel to work in a complex protein digest condition. Further, the implementation of nanofluidic logic functions with the addition of Ca2+ dramatically improves the selectivity of the nanochannel to pY peptide and thus can discern pTyr by the Tyr kinase from pSer by the Ser/Thr kinase through simultaneously monitoring multisite phosphorylation at the same or different peptide substrates in one-pot. This logic sensing platform displays the potential in differentiating Tyr kinase and Ser/Thr kinase and assessing multi-kinase activities in multi-targeted drug design.
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Affiliation(s)
- Yuting Xiong
- Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices, School of Chemistry, Biology and Materials Science, East China University of Technology, 418 Guanglan Avenue, Nanchang 330013, P. R. China.,CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Minmin Li
- Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices, School of Chemistry, Biology and Materials Science, East China University of Technology, 418 Guanglan Avenue, Nanchang 330013, P. R. China.,CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Wenqi Lu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Dongdong Wang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Mingliang Tang
- College of Life Sciences, Wuhan University, Wuhan 430072, P. R. China
| | - Yunhai Liu
- Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices, School of Chemistry, Biology and Materials Science, East China University of Technology, 418 Guanglan Avenue, Nanchang 330013, P. R. China
| | - Bing Na
- Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices, School of Chemistry, Biology and Materials Science, East China University of Technology, 418 Guanglan Avenue, Nanchang 330013, P. R. China
| | - Haijuan Qin
- Research Centre of Modern Analytical Technology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Guangyan Qing
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
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5
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Kats I, Reinbold C, Kschonsak M, Khmelinskii A, Armbruster L, Ruppert T, Knop M. Up-regulation of ubiquitin-proteasome activity upon loss of NatA-dependent N-terminal acetylation. Life Sci Alliance 2021; 5:5/2/e202000730. [PMID: 34764209 PMCID: PMC8605321 DOI: 10.26508/lsa.202000730] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 11/26/2022] Open
Abstract
Inactivation of N-terminal acetyltransferase A is found to alter Rpn4 as well as E3 ligase abundance, causing up-regulation of Ubiquitin–proteasome activity. In this context, Tom1 is also identified as a novel chain-elongating enzyme of the UFD-pathway. N-terminal acetylation is a prominent protein modification, and inactivation of N-terminal acetyltransferases (NATs) cause protein homeostasis stress. Using multiplexed protein stability profiling with linear ubiquitin fusions as reporters for the activity of the ubiquitin proteasome system, we observed increased ubiquitin proteasome system activity in NatA, but not NatB or NatC mutants. We find several mechanisms contributing to this behavior. First, NatA-mediated acetylation of the N-terminal ubiquitin–independent degron regulates the abundance of Rpn4, the master regulator of the expression of proteasomal genes. Second, the abundance of several E3 ligases involved in degradation of UFD substrates is increased in cells lacking NatA. Finally, we identify the E3 ligase Tom1 as a novel chain-elongating enzyme (E4) involved in the degradation of linear ubiquitin fusions via the formation of branched K11, K29, and K48 ubiquitin chains, independently of the known E4 ligases involved in UFD, leading to enhanced ubiquitination of the UFD substrates.
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Affiliation(s)
- Ilia Kats
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Christian Reinbold
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Marc Kschonsak
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | | | - Laura Armbruster
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Thomas Ruppert
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Michael Knop
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany .,Deutsches Krebsforschungszentrum (DKFZ), DKFZ-ZMBH Alliance, Heidelberg, Germany
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6
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Wang DY, Mou YN, Du X, Guan Y, Feng MG. Ubr1-mediated ubiquitylation orchestrates asexual development, polar growth, and virulence-related cellular events in Beauveria bassiana. Appl Microbiol Biotechnol 2021; 105:2747-2758. [PMID: 33686455 DOI: 10.1007/s00253-021-11222-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/16/2021] [Accepted: 03/04/2021] [Indexed: 01/14/2023]
Abstract
The E3 ubiquitin ligase Ubr1 is a core player in yeast ubiquitylation and protein quality control required for cellular events including proteasomal degradation and gene activity but has been rarely explored in filamentous fungi. We show here an essentiality of orthologous Ubr1-mediated ubiquitylation for the activation of central developmental pathway (CPD) and the CPD-controlled cellular events in Beauveria bassiana, a filamentous fungal insect pathogen that undergoes an asexual cycle in vitro or in vivo. As a result of ubr1 disruption, intracellular free ubiquitin accumulation increased by 1.4-fold, indicating an impaired ability for the disruptant to transfer ubiquitin to target proteins. Consequently, the disruptant was compromised in polar growth featured with curved or hook-like germ tubes and abnormally branched hyphae, leading to impeded propagation of aberrant hyphal bodies in infected insect hemocoel and attenuated virulence. In the mutant, sharply repressed expression of three CDP activator genes (brlA, abaA, and wetA) correlated well with severe defects in aerial conidiation and submerged blastospore (hyphal body) production in insect hemolymph or a mimicking medium. Moreover, the disruptant was sensitive to cell wall perturbation or lysing and showed increased catalase activity and resistance to hydrogen peroxide despite null response to high osmolarity or heat shock. Most of the examined genes involved in polar growth and cell wall integrity were down-regulated in the disruptant. These findings uncover that the Ubr1-mediated ubiquitylation orchestrates polar growth and the CDP-regulated asexual cycle in vitro and in vivo in B. bassiana. KEY POINTS: • Ubr1 is an E3 ubiquitin ligase essential for ubiquitylation in Beauveria bassiana. • Ubr1-mediated ubiquitylation is required for activation of central development pathway. • Ubr1 orchestrates polar growth and asexual cycle in vitro and in vivo.
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Affiliation(s)
- Ding-Yi Wang
- Key Laboratory of Subtropical Mountain Ecology, School of Geographical Sciences, Fujian Normal University, Fuzhou, 350007, China
| | - Ya-Ni Mou
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Zhejiang, 310058, Hangzhou, China
| | - Xi Du
- Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou University, Fuzhou, 350108, Fujian, China
| | - Yi Guan
- Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou University, Fuzhou, 350108, Fujian, China
| | - Ming-Guang Feng
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Zhejiang, 310058, Hangzhou, China.
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7
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Chen RP, Gaynor AS, Chen W. Synthetic biology approaches for targeted protein degradation. Biotechnol Adv 2019; 37:107446. [DOI: 10.1016/j.biotechadv.2019.107446] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/03/2019] [Accepted: 09/06/2019] [Indexed: 12/12/2022]
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8
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Control of Hsp90 chaperone and its clients by N-terminal acetylation and the N-end rule pathway. Proc Natl Acad Sci U S A 2017; 114:E4370-E4379. [PMID: 28515311 DOI: 10.1073/pnas.1705898114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We found that the heat shock protein 90 (Hsp90) chaperone system of the yeast Saccharomyces cerevisiae is greatly impaired in naa10Δ cells, which lack the NatA Nα-terminal acetylase (Nt-acetylase) and therefore cannot N-terminally acetylate a majority of normally N-terminally acetylated proteins, including Hsp90 and most of its cochaperones. Chk1, a mitotic checkpoint kinase and a client of Hsp90, was degraded relatively slowly in wild-type cells but was rapidly destroyed in naa10Δ cells by the Arg/N-end rule pathway, which recognized a C terminus-proximal degron of Chk1. Diverse proteins (in addition to Chk1) that are shown here to be targeted for degradation by the Arg/N-end rule pathway in naa10Δ cells include Kar4, Tup1, Gpd1, Ste11, and also, remarkably, the main Hsp90 chaperone (Hsc82) itself. Protection of Chk1 by Hsp90 could be overridden not only by ablation of the NatA Nt-acetylase but also by overexpression of the Arg/N-end rule pathway in wild-type cells. Split ubiquitin-binding assays detected interactions between Hsp90 and Chk1 in wild-type cells but not in naa10Δ cells. These and related results revealed a major role of Nt-acetylation in the Hsp90-mediated protein homeostasis, a strong up-regulation of the Arg/N-end rule pathway in the absence of NatA, and showed that a number of Hsp90 clients are previously unknown substrates of the Arg/N-end rule pathway.
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9
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Wadas B, Piatkov KI, Brower CS, Varshavsky A. Analyzing N-terminal Arginylation through the Use of Peptide Arrays and Degradation Assays. J Biol Chem 2016; 291:20976-20992. [PMID: 27510035 DOI: 10.1074/jbc.m116.747956] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Indexed: 01/29/2023] Open
Abstract
Nα-terminal arginylation (Nt-arginylation) of proteins is mediated by the Ate1 arginyltransferase (R-transferase), a component of the Arg/N-end rule pathway. This proteolytic system recognizes proteins containing N-terminal degradation signals called N-degrons, polyubiquitylates these proteins, and thereby causes their degradation by the proteasome. The definitively identified ("canonical") residues that are Nt-arginylated by R-transferase are N-terminal Asp, Glu, and (oxidized) Cys. Over the last decade, several publications have suggested (i) that Ate1 can also arginylate non-canonical N-terminal residues; (ii) that Ate1 is capable of arginylating not only α-amino groups of N-terminal residues but also γ-carboxyl groups of internal (non-N-terminal) Asp and Glu; and (iii) that some isoforms of Ate1 are specific for substrates bearing N-terminal Cys residues. In the present study, we employed arrays of immobilized 11-residue peptides and pulse-chase assays to examine the substrate specificity of mouse R-transferase. We show that amino acid sequences immediately downstream of a substrate's canonical (Nt-arginylatable) N-terminal residue, particularly a residue at position 2, can affect the rate of Nt-arginylation by R-transferase and thereby the rate of degradation of a substrate protein. We also show that the four major isoforms of mouse R-transferase have similar Nt-arginylation specificities in vitro, contrary to the claim about the specificity of some Ate1 isoforms for N-terminal Cys. In addition, we found no evidence for a significant activity of the Ate1 R-transferase toward previously invoked non-canonical N-terminal or internal amino acid residues. Together, our results raise technical concerns about earlier studies that invoked non-canonical arginylation specificities of Ate1.
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Affiliation(s)
- Brandon Wadas
- From the Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125
| | - Konstantin I Piatkov
- the Center for Biotechnology and Biomedicine, Skolkovo Institute of Science and Technology, Moscow 143026, Russia, and
| | | | - Alexander Varshavsky
- From the Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125,
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10
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Liu YJ, Liu C, Chang Z, Wadas B, Brower CS, Song ZH, Xu ZL, Shang YL, Liu WX, Wang LN, Dong W, Varshavsky A, Hu RG, Li W. Degradation of the Separase-cleaved Rec8, a Meiotic Cohesin Subunit, by the N-end Rule Pathway. J Biol Chem 2016; 291:7426-38. [PMID: 26858254 DOI: 10.1074/jbc.m116.714964] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Indexed: 02/05/2023] Open
Abstract
The Ate1 arginyltransferase (R-transferase) is a component of the N-end rule pathway, which recognizes proteins containing N-terminal degradation signals called N-degrons, polyubiquitylates these proteins, and thereby causes their degradation by the proteasome. Ate1 arginylates N-terminal Asp, Glu, or (oxidized) Cys. The resulting N-terminal Arg is recognized by ubiquitin ligases of the N-end rule pathway. In the yeastSaccharomyces cerevisiae, the separase-mediated cleavage of the Scc1/Rad21/Mcd1 cohesin subunit generates a C-terminal fragment that bears N-terminal Arg and is destroyed by the N-end rule pathway without a requirement for arginylation. In contrast, the separase-mediated cleavage of Rec8, the mammalian meiotic cohesin subunit, yields a fragment bearing N-terminal Glu, a substrate of the Ate1 R-transferase. Here we constructed and used a germ cell-confinedAte1(-/-)mouse strain to analyze the separase-generated C-terminal fragment of Rec8. We show that this fragment is a short-lived N-end rule substrate, that its degradation requires N-terminal arginylation, and that maleAte1(-/-)mice are nearly infertile, due to massive apoptotic death ofAte1(-/-)spermatocytes during the metaphase of meiosis I. These effects ofAte1ablation are inferred to be caused, at least in part, by the failure to destroy the C-terminal fragment of Rec8 in the absence of N-terminal arginylation.
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Affiliation(s)
- Yu-Jiao Liu
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, the College of Marine Life, Ocean University of China, Qingdao 266003, China, and
| | - Chao Liu
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, the University of the Chinese Academy of Sciences, Beijing 100049, China
| | - ZeNan Chang
- the Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125
| | - Brandon Wadas
- the Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125
| | - Christopher S Brower
- the Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, the Department of Biology, Texas Woman's University, Denton, Texas 76204
| | - Zhen-Hua Song
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, the University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Zhi-Liang Xu
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, the University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Yong-Liang Shang
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, the University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Wei-Xiao Liu
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Li-Na Wang
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, the University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Wen Dong
- the College of Marine Life, Ocean University of China, Qingdao 266003, China, and
| | - Alexander Varshavsky
- the Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125,
| | - Rong-Gui Hu
- the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Wei Li
- From the State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China,
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11
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Park SE, Kim JM, Seok OH, Cho H, Wadas B, Kim SY, Varshavsky A, Hwang CS. Control of mammalian G protein signaling by N-terminal acetylation and the N-end rule pathway. Science 2015; 347:1249-1252. [PMID: 25766235 PMCID: PMC4748709 DOI: 10.1126/science.aaa3844] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Rgs2, a regulator of G proteins, lowers blood pressure by decreasing signaling through Gαq. Human patients expressing Met-Leu-Rgs2 (ML-Rgs2) or Met-Arg-Rgs2 (MR-Rgs2) are hypertensive relative to people expressing wild-type Met-Gln-Rgs2 (MQ-Rgs2). We found that wild-type MQ-Rgs2 and its mutant, MR-Rgs2, were destroyed by the Ac/N-end rule pathway, which recognizes N(α)-terminally acetylated (Nt-acetylated) proteins. The shortest-lived mutant, ML-Rgs2, was targeted by both the Ac/N-end rule and Arg/N-end rule pathways. The latter pathway recognizes unacetylated N-terminal residues. Thus, the Nt-acetylated Ac-MX-Rgs2 (X = Arg, Gln, Leu) proteins are specific substrates of the mammalian Ac/N-end rule pathway. Furthermore, the Ac/N-degron of Ac-MQ-Rgs2 was conditional, and Teb4, an endoplasmic reticulum (ER) membrane-embedded ubiquitin ligase, was able to regulate G protein signaling by targeting Ac-MX-Rgs2 proteins for degradation through their N(α)-terminal acetyl group.
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Affiliation(s)
- Sang-Eun Park
- Department of Life Sciences, Pohang University of Science and
Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Jeong-Mok Kim
- Department of Life Sciences, Pohang University of Science and
Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Ok-Hee Seok
- Department of Life Sciences, Pohang University of Science and
Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Hanna Cho
- Department of Life Sciences, Pohang University of Science and
Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Brandon Wadas
- Division of Biology and Biological Engineering, California Institute
of Technology, Pasadena, CA 91125, USA
| | - Seon-Young Kim
- Medical Genomics Research Center, KRIBB, Daejeon, South Korea
- Department of Functional Genomics, University of Science and
Technology, Daejeon, South Korea
| | - Alexander Varshavsky
- Division of Biology and Biological Engineering, California Institute
of Technology, Pasadena, CA 91125, USA
| | - Cheol-Sang Hwang
- Department of Life Sciences, Pohang University of Science and
Technology, Pohang, Gyeongbuk 790-784, South Korea
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12
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Yu T, Tao Y, Yang M, Chen P, Gao X, Zhang Y, Zhang T, Chen Z, Hou J, Zhang Y, Ruan K, Wang H, Hu R. Profiling human protein degradome delineates cellular responses to proteasomal inhibition and reveals a feedback mechanism in regulating proteasome homeostasis. Cell Res 2014; 24:1214-30. [PMID: 25223703 DOI: 10.1038/cr.2014.122] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 02/14/2014] [Accepted: 06/26/2014] [Indexed: 12/15/2022] Open
Abstract
Global change in protein turnover (protein degradome) constitutes a central part of cellular responses to intrinsic or extrinsic stimuli. However, profiling protein degradome remains technically challenging. Recently, inhibition of the proteasome, e.g., by using bortezomib (BTZ), has emerged as a major chemotherapeutic strategy for treating multiple myeloma and other human malignancies, but systematic understanding of the mechanisms for BTZ drug action and tumor drug resistance is yet to be achieved. Here we developed and applied a dual-fluorescence-based Protein Turnover Assay (ProTA) to quantitatively profile global changes in human protein degradome upon BTZ-induced proteasomal inhibition. ProTA and subsequent network analyses delineate potential molecular basis for BTZ action and tumor drug resistance in BTZ chemotherapy. Finally, combined use of BTZ with drugs targeting the ProTA-identified key genes or pathways in BTZ action reduced BTZ resistance in multiple myeloma cells. Remarkably, BTZ stabilizes proteasome subunit PSMC1 and proteasome assembly factor PSMD10, suggesting a previously under-appreciated mechanism for regulating proteasome homeostasis. Therefore, ProTA is a novel tool for profiling human protein degradome to elucidate potential mechanisms of drug action and resistance, which might facilitate therapeutic development targeting proteostasis to treat human disorders.
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Affiliation(s)
- Tao Yu
- 1] State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China [2] Graduate School, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Yonghui Tao
- 1] State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China [2] Graduate School, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Meiqiang Yang
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Peng Chen
- 1] State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China [2] Graduate School, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Xiaobo Gao
- 1] State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China [2] Graduate School, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Yanbo Zhang
- 1] Graduate School, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China [2] State Key Laboratory of Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Tao Zhang
- Department of Laboratory Medicine, Hua-Shan Hospital, Fudan University, 12 Road Wulumuqi middle Road, Shanghai 200040, China
| | - Zi Chen
- Department of Hematology, Hua-Shan Hospital, Fudan University, 12 Road Wulumuqi middle Road, Shanghai 200040, China
| | - Jian Hou
- Department of Hematology, Changzheng Hospital, The Second Military Medical University, 415 Fengyang Road, Shanghai 200003, China
| | - Yan Zhang
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Kangcheng Ruan
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Hongyan Wang
- State Key Laboratory of Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Ronggui Hu
- 1] State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China [2] Cancer Research Center, SIBS-Xuhui Central Hospital, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
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13
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Functional implications and ubiquitin-dependent degradation of the peptide transporter Ptr2 in Saccharomyces cerevisiae. EUKARYOTIC CELL 2014; 13:1380-92. [PMID: 25172766 DOI: 10.1128/ec.00094-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The peptide transporter Ptr2 plays a central role in di- or tripeptide import in Saccharomyces cerevisiae. Although PTR2 transcription has been extensively analyzed in terms of upregulation by the Ubr1-Cup9 circuit, the structural and functional information for this transporter is limited. Here we identified 14 amino acid residues required for peptide import through Ptr2 based on the crystallographic information of Streptococcus thermophilus peptide transporter PepTst and based on the conservation of primary sequences among the proton-dependent oligopeptide transporters (POTs). Expression of Ptr2 carrying one of the 14 mutations of which the corresponding residues of PepTst are involved in peptide recognition, salt bridge interaction, or peptide translocation failed to enable ptr2Δtrp1 cell growth in alanyl-tryptophan (Ala-Trp) medium. We observed that Ptr2 underwent rapid degradation after cycloheximide treatment (half-life, approximately 1 h), and this degradation depended on Rsp5 ubiquitin ligase. The ubiquitination of Ptr2 most likely occurs at the N-terminal lysines 16, 27, and 34. Simultaneous substitution of arginine for the three lysines fully prevented Ptr2 degradation. Ptr2 mutants of the presumed peptide-binding site (E92Q, R93K, K205R, W362L, and E480D) exhibited severe defects in peptide import and were subjected to Rsp5-dependent degradation when cells were moved to Ala-Trp medium, whereas, similar to what occurs in the wild-type Ptr2, mutant proteins of the intracellular gate were upregulated. These results suggest that Ptr2 undergoes quality control and the defects in peptide binding and the concomitant conformational change render Ptr2 subject to efficient ubiquitination and subsequent degradation.
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14
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Analysing the substrate multispecificity of a proton-coupled oligopeptide transporter using a dipeptide library. Nat Commun 2014; 4:2502. [PMID: 24060756 PMCID: PMC3791473 DOI: 10.1038/ncomms3502] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Accepted: 08/23/2013] [Indexed: 01/26/2023] Open
Abstract
Peptide uptake systems that involve members of the proton-coupled oligopeptide transporter (POT) family are conserved across all organisms. POT proteins have characteristic substrate multispecificity, with which one transporter can recognize as many as 8,400 types of di/tripeptides and certain peptide-like drugs. Here we characterize the substrate multispecificity of Ptr2p, a major peptide transporter of Saccharomyces cerevisiae, using a dipeptide library. The affinities (Ki) of di/tripeptides toward Ptr2p show a wide distribution range from 48 mM to 0.020 mM. This substrate multispecificity indicates that POT family members have an important role in the preferential uptake of vital amino acids. In addition, we successfully establish high performance ligand affinity prediction models (97% accuracy) using our comprehensive dipeptide screening data in conjunction with simple property indices for describing ligand molecules. Our results provide an important clue to the development of highly absorbable peptides and their derivatives including peptide-like drugs. Proton-coupled oligopeptide transporters (POTs) can recognize and mediate the uptake of up to 8,400 di/tripeptides or peptide-like drugs. Ito et al. comprehensively map the substrate specificity of the yeast POT Ptr2p, and use this information to construct models for the prediction of ligand affinity.
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15
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Kim HK, Kim RR, Oh JH, Cho H, Varshavsky A, Hwang CS. The N-terminal methionine of cellular proteins as a degradation signal. Cell 2013; 156:158-69. [PMID: 24361105 DOI: 10.1016/j.cell.2013.11.031] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Revised: 09/26/2013] [Accepted: 11/20/2013] [Indexed: 11/28/2022]
Abstract
The Arg/N-end rule pathway targets for degradation proteins that bear specific unacetylated N-terminal residues while the Ac/N-end rule pathway targets proteins through their N(α)-terminally acetylated (Nt-acetylated) residues. Here, we show that Ubr1, the ubiquitin ligase of the Arg/N-end rule pathway, recognizes unacetylated N-terminal methionine if it is followed by a hydrophobic residue. This capability of Ubr1 expands the range of substrates that can be targeted for degradation by the Arg/N-end rule pathway because virtually all nascent cellular proteins bear N-terminal methionine. We identified Msn4, Sry1, Arl3, and Pre5 as examples of normal or misfolded proteins that can be destroyed through the recognition of their unacetylated N-terminal methionine. Inasmuch as proteins bearing the Nt-acetylated N-terminal methionine residue are substrates of the Ac/N-end rule pathway, the resulting complementarity of the Arg/N-end rule and Ac/N-end rule pathways enables the elimination of protein substrates regardless of acetylation state of N-terminal methionine in these substrates.
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Affiliation(s)
- Heon-Ki Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Ryu-Ryun Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Jang-Hyun Oh
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Hanna Cho
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea
| | - Alexander Varshavsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Cheol-Sang Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea.
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16
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Moir RD, Willis IM. Regulation of pol III transcription by nutrient and stress signaling pathways. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:361-75. [PMID: 23165150 DOI: 10.1016/j.bbagrm.2012.11.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 11/06/2012] [Accepted: 11/08/2012] [Indexed: 12/29/2022]
Abstract
Transcription by RNA polymerase III (pol III) is responsible for ~15% of total cellular transcription through the generation of small structured RNAs such as tRNA and 5S RNA. The coordinate synthesis of these molecules with ribosomal protein mRNAs and rRNA couples the production of ribosomes and their tRNA substrates and balances protein synthetic capacity with the growth requirements of the cell. Ribosome biogenesis in general and pol III transcription in particular is known to be regulated by nutrient availability, cell stress and cell cycle stage and is perturbed in pathological states. High throughput proteomic studies have catalogued modifications to pol III subunits, assembly, initiation and accessory factors but most of these modifications have yet to be linked to functional consequences. Here we review our current understanding of the major points of regulation in the pol III transcription apparatus, the targets of regulation and the signaling pathways known to regulate their function. This article is part of a Special Issue entitled: Transcription by Odd Pols.
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Affiliation(s)
- Robyn D Moir
- Departments of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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17
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McQueen J, van Dyk D, Young B, Loewen C, Measday V. The Mck1 GSK-3 kinase inhibits the activity of Clb2-Cdk1 post-nuclear division. Cell Cycle 2012; 11:3421-32. [PMID: 22918234 DOI: 10.4161/cc.21731] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The glycogen synthase kinase-3 homolog, Mck1, has been implicated in many cellular functions, from sporulation to calcium stress response in budding yeast. Here, we report a novel function for Mck1 in the inhibition of Clb2-Cdk1 activity post nuclear division. Clb2-Cdk1, the major mitotic cyclin-Cdk complex in yeast, accumulates before anaphase and must be inhibited in telophase for cells to exit mitosis and enter into the next cell cycle. We show that the mck1Δ mutant is highly sensitive to increased Clb2-Cdk1 activity caused either by overexpression of Clb2 or the Cdk1-activating phosphatase Mih1. Deletion of the Cdk1 inhibitory kinase, SWE1, in combination with a mck1Δ mutant results in a synthetic growth defect, suggesting that Mck1 and Swe1 function in parallel pathways to inhibit Clb2-Cdk1. We find that mck1Δ strains have a delay in mitotic exit as well as elevated levels of Clb2-Cdk1 activity post-nuclear division. Using a co-immunoprecipitation assay, we identify a physical interaction between Mck1 and both Clb2 and Mih1. Finally, we demonstrate that phosphorylation of purified Clb2 by Cdk1 is inhibited by catalytically active Mck1 but not catalytically inactive Mck1 in vitro. We propose that Mck1 inhibits the activity of Clb2-Cdk1 via interaction with Clb2. The mammalian glycogen synthase kinase-3 homolog has been implicated in cyclin inhibition, suggesting a conserved cell cycle function for both yeast and mammalian glycogen synthase kinases.
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Affiliation(s)
- Jennifer McQueen
- Genetics Graduate Program; University of British Columbia; Vancouver, BC Canada
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18
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Affiliation(s)
- Alexander Varshavsky
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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19
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Regulation of amino acid, nucleotide, and phosphate metabolism in Saccharomyces cerevisiae. Genetics 2012; 190:885-929. [PMID: 22419079 DOI: 10.1534/genetics.111.133306] [Citation(s) in RCA: 338] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Ever since the beginning of biochemical analysis, yeast has been a pioneering model for studying the regulation of eukaryotic metabolism. During the last three decades, the combination of powerful yeast genetics and genome-wide approaches has led to a more integrated view of metabolic regulation. Multiple layers of regulation, from suprapathway control to individual gene responses, have been discovered. Constitutive and dedicated systems that are critical in sensing of the intra- and extracellular environment have been identified, and there is a growing awareness of their involvement in the highly regulated intracellular compartmentalization of proteins and metabolites. This review focuses on recent developments in the field of amino acid, nucleotide, and phosphate metabolism and provides illustrative examples of how yeast cells combine a variety of mechanisms to achieve coordinated regulation of multiple metabolic pathways. Importantly, common schemes have emerged, which reveal mechanisms conserved among various pathways, such as those involved in metabolite sensing and transcriptional regulation by noncoding RNAs or by metabolic intermediates. Thanks to the remarkable sophistication offered by the yeast experimental system, a picture of the intimate connections between the metabolomic and the transcriptome is becoming clear.
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Abstract
The N-end rule pathway is a proteolytic system in which N-terminal residues of short-lived proteins are recognized by recognition components (N-recognins) as essential components of degrons, called N-degrons. Known N-recognins in eukaryotes mediate protein ubiquitylation and selective proteolysis by the 26S proteasome. Substrates of N-recognins can be generated when normally embedded destabilizing residues are exposed at the N terminus by proteolytic cleavage. N-degrons can also be generated through modifications of posttranslationally exposed pro-N-degrons of otherwise stable proteins; such modifications include oxidation, arginylation, leucylation, phenylalanylation, and acetylation. Although there are variations in components, degrons, and hierarchical structures, the proteolytic systems based on generation and recognition of N-degrons have been observed in all eukaryotes and prokaryotes examined thus far. The N-end rule pathway regulates homeostasis of various physiological processes, in part, through interaction with small molecules. Here, we review the biochemical mechanisms, structures, physiological functions, and small-molecule-mediated regulation of the N-end rule pathway.
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Affiliation(s)
- Takafumi Tasaki
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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21
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Abstract
Many intracellular proteins are metabolically unstable or can become unstable during their lifetime in a cell. The in vivo half-lives of specific proteins range from less than a minute to many days. Among the functions of intracellular proteolysis are the elimination of misfolded or otherwise abnormal proteins; maintenance of amino acid pools in cells affected by stresses such as starvation; and generation of protein fragments that act as hormones, antigens, or other effectors. One major function of proteolytic pathways is the selective destruction of proteins whose concentrations must vary with time and alterations in the state of a cell. Short in vivo half-lives of such proteins provide a way to generate their spatial gradients and to rapidly adjust their concentration or subunit composition through changes in the rate of their degradation. The regulated (and processive) degradation of intracellular proteins is carried out largely by the ubiquitin-proteasome system (Ub system), in conjunction with autophagy-lysosome pathways. Other contributors to intracellular proteolysis include cytosolic and nuclear proteases, such as caspases, calpains, and separases. They often function as "upstream" components of the Ub system, which destroys protein fragments that had been produced by these (nonprocessive) proteases. Ub, a 76-residue protein, mediates selective proteolysis through its enzymatic conjugation to proteins that contain primary degradation signals (degrons (1)), thereby marking such proteins for degradation by the 26S proteasome, an ATP-dependent multisubunit protease. Ub conjugation involves the formation of a poly-Ub chain that is linked (in most cases) to the ε-amino group of an internal Lys residue in a substrate protein. Ub is a "secondary" degron, in that Ub is conjugated to proteins that contain primary degradation signals.
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22
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Hwang CS, Sukalo M, Batygin O, Addor MC, Brunner H, Aytes AP, Mayerle J, Song HK, Varshavsky A, Zenker M. Ubiquitin ligases of the N-end rule pathway: assessment of mutations in UBR1 that cause the Johanson-Blizzard syndrome. PLoS One 2011; 6:e24925. [PMID: 21931868 PMCID: PMC3172311 DOI: 10.1371/journal.pone.0024925] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 08/19/2011] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Johanson-Blizzard syndrome (JBS; OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, facial dysmorphism with the characteristic nasal wing hypoplasia, multiple malformations, and frequent mental retardation. Our previous work has shown that JBS is caused by mutations in human UBR1, which encodes one of the E3 ubiquitin ligases of the N-end rule pathway. The N-end rule relates the regulation of the in vivo half-life of a protein to the identity of its N-terminal residue. One class of degradation signals (degrons) recognized by UBR1 are destabilizing N-terminal residues of protein substrates. METHODOLOGY/PRINCIPAL FINDINGS Most JBS-causing alterations of UBR1 are nonsense, frameshift or splice-site mutations that abolish UBR1 activity. We report here missense mutations of human UBR1 in patients with milder variants of JBS. These single-residue changes, including a previously reported missense mutation, involve positions in the RING-H2 and UBR domains of UBR1 that are conserved among eukaryotes. Taking advantage of this conservation, we constructed alleles of the yeast Saccharomyces cerevisiae UBR1 that were counterparts of missense JBS-UBR1 alleles. Among these yeast Ubr1 mutants, one of them (H160R) was inactive in yeast-based activity assays, the other one (Q1224E) had a detectable but weak activity, and the third one (V146L) exhibited a decreased but significant activity, in agreement with manifestations of JBS in the corresponding JBS patients. CONCLUSIONS/SIGNIFICANCE These results, made possible by modeling defects of a human ubiquitin ligase in its yeast counterpart, verified and confirmed the relevance of specific missense UBR1 alleles to JBS, and suggested that a residual activity of a missense allele is causally associated with milder variants of JBS.
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Affiliation(s)
- Cheol-Sang Hwang
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | - Maja Sukalo
- Institute of Human Genetics, University Hospital, Magdeburg, Germany
| | - Olga Batygin
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | | | - Han Brunner
- Department of Human Genetics, University Medical Center Nijmegen, Nijmegen, The Netherlands
| | - Antonio Perez Aytes
- Dismorfologia y Genetica Reproductiva, Grupo de Investigacion en Perinatologia, Instituto de Investigacion Sanitari, Fundacion Hospital La Fe, Valencia, Spain
| | - Julia Mayerle
- Department of Gastroenterology and Nutrition, University Hospital, Greifswald, Germany
| | - Hyun Kyu Song
- School of Life Sciences and Biotechnology, Korea University, Seoul, South Korea
| | - Alexander Varshavsky
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
- * E-mail: (AV); (MZ)
| | - Martin Zenker
- Institute of Human Genetics, University Hospital, Magdeburg, Germany
- Institute of Human Genetics, University Hospital Erlangen, University of Erlangen-Nuremberg, Erlangen, Germany
- * E-mail: (AV); (MZ)
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23
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Varshavsky A. The N-end rule pathway and regulation by proteolysis. Protein Sci 2011; 20:1298-345. [PMID: 21633985 PMCID: PMC3189519 DOI: 10.1002/pro.666] [Citation(s) in RCA: 509] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 05/16/2011] [Accepted: 05/18/2011] [Indexed: 01/12/2023]
Abstract
The N-end rule relates the regulation of the in vivo half-life of a protein to the identity of its N-terminal residue. Degradation signals (degrons) that are targeted by the N-end rule pathway include a set called N-degrons. The main determinant of an N-degron is a destabilizing N-terminal residue of a protein. In eukaryotes, the N-end rule pathway is a part of the ubiquitin system and consists of two branches, the Ac/N-end rule and the Arg/N-end rule pathways. The Ac/N-end rule pathway targets proteins containing N(α) -terminally acetylated (Nt-acetylated) residues. The Arg/N-end rule pathway recognizes unacetylated N-terminal residues and involves N-terminal arginylation. Together, these branches target for degradation a majority of cellular proteins. For example, more than 80% of human proteins are cotranslationally Nt-acetylated. Thus most proteins harbor a specific degradation signal, termed (Ac)N-degron, from the moment of their birth. Specific N-end rule pathways are also present in prokaryotes and in mitochondria. Enzymes that produce N-degrons include methionine-aminopeptidases, caspases, calpains, Nt-acetylases, Nt-amidases, arginyl-transferases and leucyl-transferases. Regulated degradation of specific proteins by the N-end rule pathway mediates a legion of physiological functions, including the sensing of heme, oxygen, and nitric oxide; selective elimination of misfolded proteins; the regulation of DNA repair, segregation and condensation; the signaling by G proteins; the regulation of peptide import, fat metabolism, viral and bacterial infections, apoptosis, meiosis, spermatogenesis, neurogenesis, and cardiovascular development; and the functioning of adult organs, including the pancreas and the brain. Discovered 25 years ago, this pathway continues to be a fount of biological insights.
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Affiliation(s)
- Alexander Varshavsky
- 1Division of Biology, California Institute of Technology, Pasadena, California 91125.
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24
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Dougan DA, Micevski D, Truscott KN. The N-end rule pathway: from recognition by N-recognins, to destruction by AAA+proteases. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:83-91. [PMID: 21781991 DOI: 10.1016/j.bbamcr.2011.07.002] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 07/03/2011] [Accepted: 07/06/2011] [Indexed: 11/26/2022]
Abstract
Intracellular proteolysis is a tightly regulated process responsible for the targeted removal of unwanted or damaged proteins. The non-lysosomal removal of these proteins is performed by processive enzymes, which belong to the AAA+superfamily, such as the 26S proteasome and Clp proteases. One important protein degradation pathway, that is common to both prokaryotes and eukaryotes, is the N-end rule. In this pathway, proteins bearing a destabilizing amino acid residue at their N-terminus are degraded either by the ClpAP protease in bacteria, such as Escherichia coli or by the ubiquitin proteasome system in the eukaryotic cytoplasm. A suite of enzymes and other molecular components are also required for the successful generation, recognition and delivery of N-end rule substrates to their cognate proteases. In this review we examine the similarities and differences in the N-end rule pathway of bacterial and eukaryotic systems, focusing on the molecular determinants of this pathway.
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Affiliation(s)
- D A Dougan
- Department of Biochemistry, L Trobe Institute for Molecular Science, La Trobe University, Melbourne, 3086, Australia.
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25
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Papanayotou I, Sun B, Roth AF, Davis NG. Protein aggregation induced during glass bead lysis of yeast. Yeast 2011; 27:801-16. [PMID: 20641011 DOI: 10.1002/yea.1771] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Yeast cell lysates produced by mechanical glass bead disruption are widely used in a variety of applications, including for the analysis of native function, e.g. protein-protein interaction, enzyme assays and membrane fractionations. Below, we report a striking case of protein denaturation and aggregation that is induced by this lysis protocol. Most of this analysis focuses on the type 1 casein kinase Yck2, which normally tethers to the plasma membrane through C-terminal palmitoylation. Surprisingly, when cells are subjected to glass bead disruption, non-palmitoylated, cytosolic forms of the kinase denature and aggregate, while membrane-associated forms, whether attached through their native palmitoyl tethers or through a variety of artificial membrane-tethering sequences, are wholly protected from denaturation and aggregation. A wider look at the yeast proteome finds that, while the majority of proteins resist glass bead-induced aggregation, a significant subset does, in fact, succumb to such denaturation. Thus, yeast researchers should be aware of this potential artifact when embarking on biochemical analyses that employ glass bead lysates to look at native protein function. Finally, we demonstrate an experimental utility for glass bead-induced aggregation, using its fine discrimination of membrane-associated from non-associated Yck2 forms to discern fractional palmitoylation states of Yck2 mutants that are partially defective for palmitoylation.
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Affiliation(s)
- Irene Papanayotou
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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26
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Hwang CS, Shemorry A, Auerbach D, Varshavsky A. The N-end rule pathway is mediated by a complex of the RING-type Ubr1 and HECT-type Ufd4 ubiquitin ligases. Nat Cell Biol 2010; 12:1177-85. [PMID: 21076411 PMCID: PMC3003441 DOI: 10.1038/ncb2121] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Accepted: 10/18/2010] [Indexed: 02/07/2023]
Abstract
Substrates of the N-end rule pathway are recognized by the Ubr1 E3 ubiquitin ligase through their destabilizing N-terminal residues. Our previous work showed that the Ubr1 E3 and the Ufd4 E3 co-target an internal degron of the Mgt1 DNA repair protein. Ufd4 is an E3 of the ubiquitin-fusion degradation (UFD) pathway that recognizes an N-terminal ubiquitin moiety. Here we report that the RING-type Ubr1 E3 and the HECT-type Ufd4 E3 interact, both physically and functionally. Although Ubr1 can recognize and polyubiquitylate an N-end rule substrate in the absence of Ufd4, the Ubr1-Ufd4 complex is more processive in that it produces a longer substrate-linked polyubiquitin chain. Conversely, Ubr1 can function as a polyubiquitylation-enhancing component of the Ubr1-Ufd4 complex in its targeting of UFD substrates. We also found that Ubr1 can recognize the N-terminal ubiquitin moiety. These and related advances unify two proteolytic systems that have been studied separately over two decades.
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Affiliation(s)
- Cheol-Sang Hwang
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA
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27
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Graciet E, Wellmer F. The plant N-end rule pathway: structure and functions. TRENDS IN PLANT SCIENCE 2010; 15:447-453. [PMID: 20627801 DOI: 10.1016/j.tplants.2010.04.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2010] [Revised: 04/25/2010] [Accepted: 04/29/2010] [Indexed: 05/29/2023]
Abstract
The N-end rule pathway is a protein degradation pathway that relates the stability of a protein to the nature of its N-terminal amino acid residue. This pathway is part of the ubiquitin-proteasome system in eukaryotes and has been shown to be involved in a multitude of cellular and developmental processes in animals and fungi. However, in plants, its structure and functions have long been enigmatic. In this review, we discuss recent advances in the identification of the enzymatic components that mediate protein degradation through the N-end rule pathway in plants. We further describe the known functions of this pathway in the control of plant growth and development and outline open questions that will likely be the focus of future research.
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Affiliation(s)
- Emmanuelle Graciet
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland.
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Brower CS, Veiga L, Jones RH, Varshavsky A. Mouse Dfa is a repressor of TATA-box promoters and interacts with the Abt1 activator of basal transcription. J Biol Chem 2010; 285:17218-34. [PMID: 20356838 DOI: 10.1074/jbc.m110.118638] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Our study of the mouse Ate1 arginyltransferase, a component of the N-end rule pathway, has shown that Ate1 pre-mRNA is produced from a bidirectional promoter that also expresses, in the opposite direction, a previously uncharacterized gene (Hu, R. G., Brower, C. S., Wang, H., Davydov, I. V., Sheng, J., Zhou, J., Kwon, Y. T., and Varshavsky, A. (2006) J. Biol. Chem. 281, 32559-32573). In this work, we began analyzing this gene, termed Dfa (divergent from Ate1). Mouse Dfa was found to be transcribed from both the bidirectional P(Ate1/Dfa) promoter and other nearby promoters. The resulting transcripts are alternatively spliced, yielding a complex set of Dfa mRNAs that are present largely, although not exclusively, in the testis. A specific Dfa mRNA encodes, via its 3'-terminal exon, a 217-residue protein termed Dfa(A). Other Dfa mRNAs also contain this exon. Dfa(A) is sequelogous (similar in sequence) to a region of the human/mouse HTEX4 protein, whose physiological function is unknown. We produced an affinity-purified antibody to recombinant mouse Dfa(A) that detected a 35-kDa protein in the mouse testis and in several cell lines. Experiments in which RNA interference was used to down-regulate Dfa indicated that the 35-kDa protein was indeed Dfa(A). Furthermore, Dfa(A) was present in the interchromatin granule clusters and was also found to bind to the Ggnbp1 gametogenetin-binding protein-1 and to the Abt1 activator of basal transcription that interacts with the TATA-binding protein. Given these results, RNA interference was used to probe the influence of Dfa levels in luciferase reporter assays. We found that Dfa(A) acts as a repressor of TATA-box transcriptional promoters.
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Affiliation(s)
- Christopher S Brower
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA
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Hwang CS, Shemorry A, Varshavsky A. N-terminal acetylation of cellular proteins creates specific degradation signals. Science 2010; 327:973-7. [PMID: 20110468 DOI: 10.1126/science.1183147] [Citation(s) in RCA: 493] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The retained N-terminal methionine (Met) residue of a nascent protein is often N-terminally acetylated (Nt-acetylated). Removal of N-terminal Met by Met-aminopeptidases frequently leads to Nt-acetylation of the resulting N-terminal alanine (Ala), valine (Val), serine (Ser), threonine (Thr), and cysteine (Cys) residues. Although a majority of eukaryotic proteins (for example, more than 80% of human proteins) are cotranslationally Nt-acetylated, the function of this extensively studied modification is largely unknown. Using the yeast Saccharomyces cerevisiae, we found that the Nt-acetylated Met residue could act as a degradation signal (degron), targeted by the Doa10 ubiquitin ligase. Moreover, Doa10 also recognized the Nt-acetylated Ala, Val, Ser, Thr, and Cys residues. Several examined proteins of diverse functions contained these N-terminal degrons, termed AcN-degrons, which are a prevalent class of degradation signals in cellular proteins.
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Affiliation(s)
- Cheol-Sang Hwang
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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Brower CS, Varshavsky A. Ablation of arginylation in the mouse N-end rule pathway: loss of fat, higher metabolic rate, damaged spermatogenesis, and neurological perturbations. PLoS One 2009; 4:e7757. [PMID: 19915679 PMCID: PMC2773024 DOI: 10.1371/journal.pone.0007757] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 10/13/2009] [Indexed: 12/30/2022] Open
Abstract
In the N-end rule pathway of protein degradation, the destabilizing activity of N-terminal Asp, Glu or (oxidized) Cys residues requires their conjugation to Arg, which is recognized directly by pathway's ubiquitin ligases. N-terminal arginylation is mediated by the Ate1 arginyltransferase, whose physiological substrates include the Rgs4, Rgs5 and Rgs16 regulators of G proteins. Here, we employed the Cre-lox technique to uncover new physiological functions of N-terminal arginylation in adult mice. We show that postnatal deletion of mouse Ate1 (its unconditional deletion is embryonic lethal) causes a rapid decrease of body weight and results in early death of approximately 15% of Ate1-deficient mice. Despite being hyperphagic, the surviving Ate1-deficient mice contain little visceral fat. They also exhibit an increased metabolic rate, ectopic induction of the Ucp1 uncoupling protein in white fat, and are resistant to diet-induced obesity. In addition, Ate1-deficient mice have enlarged brains, an enhanced startle response, are strikingly hyperkinetic, and are prone to seizures and kyphosis. Ate1-deficient males are also infertile, owing to defects in Ate1(-/-) spermatocytes. The remarkably broad range of specific biological processes that are shown here to be perturbed by the loss of N-terminal arginylation will make possible the dissection of regulatory circuits that involve Ate1 and either its known substrates, such as Rgs4, Rgs5 and Rgs16, or those currently unknown.
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Affiliation(s)
- Christopher S. Brower
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | - Alexander Varshavsky
- Division of Biology, California Institute of Technology, Pasadena, California, United States of America
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Wang H, Piatkov KI, Brower CS, Varshavsky A. Glutamine-specific N-terminal amidase, a component of the N-end rule pathway. Mol Cell 2009; 34:686-95. [PMID: 19560421 DOI: 10.1016/j.molcel.2009.04.032] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 04/14/2009] [Accepted: 04/24/2009] [Indexed: 11/15/2022]
Abstract
Deamidation of N-terminal Gln by Nt(Q)-amidase, an N-terminal amidohydrolase, is a part of the N-end rule pathway of protein degradation. We detected the activity of Nt(Q)-amidase, termed Ntaq1, in mouse tissues, purified Ntaq1 from bovine brains, identified its gene, and began analyzing this enzyme. Ntaq1 is highly conserved among animals, plants, and some fungi, but its sequence is dissimilar to sequences of other amidases. An earlier mutant in the Drosophila Cg8253 gene that we show here to encode Nt(Q)-amidase has defective long-term memory. Other studies identified protein ligands of the uncharacterized human C8orf32 protein that we show here to be the Ntaq1 Nt(Q)-amidase. Remarkably, "high-throughput" studies have recently solved the crystal structure of C8orf32 (Ntaq1). Our site-directed mutagenesis of Ntaq1 and its crystal structure indicate that the active site and catalytic mechanism of Nt(Q)-amidase are similar to those of transglutaminases.
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Affiliation(s)
- Haiqing Wang
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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Two proteolytic pathways regulate DNA repair by cotargeting the Mgt1 alkylguanine transferase. Proc Natl Acad Sci U S A 2009; 106:2142-7. [PMID: 19164530 DOI: 10.1073/pnas.0812316106] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
O(6)-methylguanine (O(6)meG) and related modifications of guanine in double-stranded DNA are functionally severe lesions that can be produced by many alkylating agents, including N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a potent carcinogen. O(6)meG is repaired through its demethylation by the O(6)-alkylguanine-DNA alkyltransferase (AGT). This protein is called Mgmt (or MGMT) in mammals and Mgt1 in the yeast Saccharomyces cerevisiae. AGT proteins remove methyl and other alkyl groups from an alkylated O(6) in guanine by transferring the adduct to an active-site cysteine residue. The resulting S-alkyl-Cys of AGT is not restored back to Cys, so repair proteins of this kind can act only once. We report here that S. cerevisiae Mgt1 is cotargeted for degradation, through a degron near its N terminus, by 2 ubiquitin-mediated proteolytic systems, the Ubr1/Rad6-dependent N-end rule pathway and the Ufd4/Ubc4-dependent ubiquitin fusion degradation (UFD) pathway. The cotargeting of Mgt1 by these pathways is synergistic, in that it increases not only the yield of polyubiquitylated Mgt1, but also the processivity of polyubiquitylation. The N-end rule and UFD pathways comediate both the constitutive and MNNG-accelerated degradation of Mgt1. Yeast cells lacking the Ubr1 and Ufd4 ubiquitin ligases were hyperresistant to MNNG but hypersensitive to the toxicity of overexpressed Mgt1. We consider ramifications of this discovery for the control of DNA repair and mechanisms of substrate targeting by the ubiquitin system.
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