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Xie W, Sowemimo I, Hayashi R, Wang J, Burkard TR, Brennecke J, Ameres SL, Patel DJ. Structure-function analysis of microRNA 3'-end trimming by Nibbler. Proc Natl Acad Sci U S A 2020; 117:30370-30379. [PMID: 33199607 PMCID: PMC7720153 DOI: 10.1073/pnas.2018156117] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Nibbler (Nbr) is a 3'-to-5' exoribonuclease whose catalytic 3'-end trimming activity impacts microRNA (miRNA) and PIWI-interacting RNA (piRNA) biogenesis. Here, we report on structural and functional studies to decipher the contributions of Nbr's N-terminal domain (NTD) and exonucleolytic domain (EXO) in miRNA 3'-end trimming. We have solved the crystal structures of the NTD core and EXO domains of Nbr, both in the apo-state. The NTD-core domain of Aedes aegypti Nbr adopts a HEAT-like repeat scaffold with basic patches constituting an RNA-binding surface exhibiting a preference for binding double-strand RNA (dsRNA) over single-strand RNA (ssRNA). Structure-guided functional assays in Drosophila S2 cells confirmed a principal role of the NTD in exonucleolytic miRNA trimming, which depends on basic surface patches. Gain-of-function experiments revealed a potential role of the NTD in recruiting Nbr to Argonaute-bound small RNA substrates. The EXO domain of A. aegypti and Drosophila melanogaster Nbr adopt a mixed α/β-scaffold with a deep pocket lined by a DEDDy catalytic cleavage motif. We demonstrate that Nbr's EXO domain exhibits Mn2+-dependent ssRNA-specific 3'-to-5' exoribonuclease activity. Modeling of a 3' terminal Uridine into the catalytic pocket of Nbr EXO indicates that 2'-O-methylation of the 3'-U would result in a steric clash with a tryptophan side chain, suggesting that 2'-O-methylation protects small RNAs from Nbr-mediated trimming. Overall, our data establish that Nbr requires its NTD as a substrate recruitment platform to execute exonucleolytic miRNA maturation, catalyzed by the ribonuclease EXO domain.
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Affiliation(s)
- Wei Xie
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
| | - Ivica Sowemimo
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria
| | - Rippei Hayashi
- Department of Genome Sciences, The John Curtin School of Medical Research, Australian National University, Canberra 2601, Australia
| | - Juncheng Wang
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
| | - Thomas R Burkard
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria
| | - Julius Brennecke
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria;
| | - Stefan L Ameres
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria;
- Max Perutz Labs, University of Vienna, Vienna BioCenter, 1030 Vienna, Austria
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065;
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Hara K, Kinoshita K, Migita T, Murakami K, Shimizu K, Takeuchi K, Hirano T, Hashimoto H. Structural basis of HEAT-kleisin interactions in the human condensin I subcomplex. EMBO Rep 2019; 20:embr.201847183. [PMID: 30858338 PMCID: PMC6501013 DOI: 10.15252/embr.201847183] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 02/13/2019] [Accepted: 02/20/2019] [Indexed: 12/30/2022] Open
Abstract
Condensin I is a multi‐protein complex that plays an essential role in mitotic chromosome assembly and segregation in eukaryotes. It is composed of five subunits: two SMC (SMC2 and SMC4), a kleisin (CAP‐H), and two HEAT‐repeat (CAP‐D2 and CAP‐G) subunits. Although balancing acts of the two HEAT‐repeat subunits have been demonstrated to enable this complex to support the dynamic assembly of chromosomal axes in vertebrate cells, its underlying mechanisms remain poorly understood. Here, we report the crystal structure of a human condensin I subcomplex comprising hCAP‐G and hCAP‐H. hCAP‐H binds to the concave surfaces of a harp‐shaped HEAT‐repeat domain of hCAP‐G. Physical interaction between hCAP‐G and hCAP‐H is indeed essential for mitotic chromosome assembly recapitulated in Xenopus egg cell‐free extracts. Furthermore, this study reveals that the human CAP‐G‐H subcomplex has the ability to interact with not only double‐stranded DNA, but also single‐stranded DNA, suggesting functional divergence of the vertebrate condensin I complex in proper mitotic chromosome assembly.
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Affiliation(s)
- Kodai Hara
- Department of Physical Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | | | - Tomoko Migita
- Department of Physical Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Kei Murakami
- Department of Physical Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Kenichiro Shimizu
- Department of Physical Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Kozo Takeuchi
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | - Tatsuya Hirano
- Chromosome Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | - Hiroshi Hashimoto
- Department of Physical Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
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Colina-Tenorio L, Miranda-Astudillo H, Dautant A, Vázquez-Acevedo M, Giraud MF, González-Halphen D. Subunit Asa3 ensures the attachment of the peripheral stalk to the membrane sector of the dimeric ATP synthase of Polytomella sp. Biochem Biophys Res Commun 2018; 509:341-347. [PMID: 30585150 DOI: 10.1016/j.bbrc.2018.12.142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 12/19/2018] [Indexed: 02/04/2023]
Abstract
The mitochondrial ATP synthase of Polytomella exhibits a peripheral stalk and a dimerization domain built by the Asa subunits, unique to chlorophycean algae. The topology of these subunits has been extensively studied. Here we explored the interactions of subunit Asa3 using Far Western blotting and subcomplex reconstitution, and found it associates with Asa1 and Asa8. We also identified the novel interactions Asa1-Asa2 and Asa1-Asa7. In silico analyses of Asa3 revealed that it adopts a HEAT repeat-like structure that points to its location within the enzyme based on the available 3D-map of the algal ATP synthase. We suggest that subunit Asa3 is instrumental in securing the attachment of the peripheral stalk to the membrane sector, thus stabilizing the dimeric mitochondrial ATP synthase.
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Affiliation(s)
- Lilia Colina-Tenorio
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | | | - Alain Dautant
- CNRS, UMR5095, IBGC, Bordeaux, France; Energy Transducing Systems and Mitochondrial Morphology, Université de Bordeaux, Bordeaux, France
| | - Miriam Vázquez-Acevedo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Marie-France Giraud
- CNRS, UMR5095, IBGC, Bordeaux, France; Energy Transducing Systems and Mitochondrial Morphology, Université de Bordeaux, Bordeaux, France
| | - Diego González-Halphen
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico.
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Hill A, Niles B, Cuyegkeng A, Powers T. Redesigning TOR Kinase to Explore the Structural Basis for TORC1 and TORC2 Assembly. Biomolecules 2018; 8:biom8020036. [PMID: 29865216 PMCID: PMC6023025 DOI: 10.3390/biom8020036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 05/25/2018] [Accepted: 05/25/2018] [Indexed: 12/21/2022] Open
Abstract
TOR is a serine/threonine protein kinase that assembles into distinct TOR Complexes 1 and 2 (TORC1 or TORC2) to regulate cell growth. In mammalian cells, a single mTOR incorporates stably into mTORC1 and mTORC2. By contrast, in Saccharomyces cerevisiae, two highly similar Tor1 and Tor2 proteins exist, where Tor1 assembles exclusively into TORC1 and Tor2 assembles preferentially into TORC2. To gain insight into TOR complex assembly, we used this bifurcation in yeast to identify structural elements within Tor1 and Tor2 that govern their complex specificity. We have identified a concise region of ~500 amino acids within the N-terminus of Tor2, which we term the Major Assembly Specificity (MAS) domain, that is sufficient to confer significant TORC2 activity when placed into an otherwise Tor1 protein. Consistently, introduction of the corresponding MAS domain from Tor1 into an otherwise Tor2 is sufficient to confer stable association with TORC1-specific components. Remarkably, much like mTOR, this latter chimera also retains stable interactions with TORC2 components, indicating that determinants throughout Tor1/Tor2 contribute to complex specificity. Our findings are in excellent agreement with recent ultrastructural studies of TORC1 and TORC2, where the MAS domain is involved in quaternary interactions important for complex formation and/or stability.
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Affiliation(s)
- Andrew Hill
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
| | - Brad Niles
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
| | - Andrew Cuyegkeng
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
| | - Ted Powers
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
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Shin B, Jung R, Oh H, Owens GE, Lee H, Kwak S, Lee R, Cotman SL, Lee JM, MacDonald ME, Song JJ, Vijayvargia R, Seong IS. Novel DNA Aptamers that Bind to Mutant Huntingtin and Modify Its Activity. Mol Ther Nucleic Acids 2018; 11:416-428. [PMID: 29858077 PMCID: PMC5992459 DOI: 10.1016/j.omtn.2018.03.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 02/22/2018] [Accepted: 03/13/2018] [Indexed: 12/28/2022]
Abstract
The CAG repeat expansion that elongates the polyglutamine tract in huntingtin is the root genetic cause of Huntington’s disease (HD), a debilitating neurodegenerative disorder. This seemingly slight change to the primary amino acid sequence alters the physical structure of the mutant protein and alters its activity. We have identified a set of G-quadruplex-forming DNA aptamers (MS1, MS2, MS3, MS4) that bind mutant huntingtin proximal to lysines K2932/K2934 in the C-terminal CTD-II domain. Aptamer binding to mutant huntingtin abrogated the enhanced polycomb repressive complex 2 (PRC2) stimulatory activity conferred by the expanded polyglutamine tract. In HD, but not normal, neuronal progenitor cells (NPCs), MS3 aptamer co-localized with endogenous mutant huntingtin and was associated with significantly decreased PRC2 activity. Furthermore, MS3 transfection protected HD NPCs against starvation-dependent stress with increased ATP. Therefore, DNA aptamers can preferentially target mutant huntingtin and modulate a gain of function endowed by the elongated polyglutamine segment. These mutant huntingtin binding aptamers provide novel molecular tools for delineating the effects of the HD mutation and encourage mutant huntingtin structure-based approaches to therapeutic development.
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Affiliation(s)
- Baehyun Shin
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Roy Jung
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Hyejin Oh
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Gwen E Owens
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Hyeongseok Lee
- Department of Biological Sciences, KAIST Institute for the BioCentury, Center for Cancer Metastasis, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Seung Kwak
- CHDI Foundation, Princeton, NJ 08540, USA
| | - Ramee Lee
- CHDI Foundation, Princeton, NJ 08540, USA
| | - Susan L Cotman
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Jong-Min Lee
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Marcy E MacDonald
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Ji-Joon Song
- Department of Biological Sciences, KAIST Institute for the BioCentury, Center for Cancer Metastasis, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Ravi Vijayvargia
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA.
| | - Ihn Sik Seong
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02114, USA.
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Moriyama K, Yoshizawa-Sugata N, Masai H. Oligomer formation and G-quadruplex binding by purified murine Rif1 protein, a key organizer of higher-order chromatin architecture. J Biol Chem 2018; 293:3607-3624. [PMID: 29348174 DOI: 10.1074/jbc.ra117.000446] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 12/21/2017] [Indexed: 11/06/2022] Open
Abstract
Rap1-interacting protein 1 (Rif1) regulates telomere length in budding yeast. We previously reported that, in metazoans and fission yeast, Rif1 also plays pivotal roles in controlling genome-wide DNA replication timing. We proposed that Rif1 may assemble chromatin compartments that contain specific replication-timing domains by promoting chromatin loop formation. Rif1 also is involved in DNA lesion repair, restart after replication fork collapse, anti-apoptosis activities, replicative senescence, and transcriptional regulation. Although multiple physiological functions of Rif1 have been characterized, biochemical and structural information on mammalian Rif1 is limited, mainly because of difficulties in purifying the full-length protein. Here, we expressed and purified the 2418-amino-acid-long, full-length murine Rif1 as well as its partially truncated variants in human 293T cells. Hydrodynamic analyses indicated that Rif1 forms elongated or extended homo-oligomers in solution, consistent with the presence of a HEAT-type helical repeat segment known to adopt an elongated shape. We also observed that the purified murine Rif1 bound G-quadruplex (G4) DNA with high specificity and affinity, as was previously shown for Rif1 from fission yeast. Both the N-terminal (HEAT-repeat) and C-terminal segments were involved in oligomer formation and specifically bound G4 DNA, and the central intrinsically disordered polypeptide segment increased the affinity for G4. Of note, pulldown assays revealed that Rif1 simultaneously binds multiple G4 molecules. Our findings support a model in which Rif1 modulates chromatin loop structures through binding to multiple G4 assemblies and by holding chromatin fibers together.
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Affiliation(s)
- Kenji Moriyama
- From the Genome Dynamics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Naoko Yoshizawa-Sugata
- From the Genome Dynamics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Hisao Masai
- From the Genome Dynamics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
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Abstract
The steps leading to constitutive exocytosis are poorly understood. In Dictyostelium WASH complex mutants, exocytosis is blocked, so cells that take up fluorescent dextran from the medium retain it and remain fluorescent. Here, we establish a FACS-based method to select cells that retain fluorescent dextran, allowing identification of mutants with disrupted exocytosis. Screening a pool of random mutants identified members of the WASH complex, as expected, and multiple mutants in the conserved HEAT-repeat-containing protein Mroh1. In mroh1 mutants, endosomes develop normally until the stage where lysosomes neutralize to postlysosomes, but thereafter the WASH complex is recycled inefficiently, and subsequent exocytosis is substantially delayed. Mroh1 protein localizes to lysosomes in mammalian and Dictyostelium cells. In Dictyostelium, it accumulates on lysosomes as they mature and is removed, together with the WASH complex, shortly before the postlysosomes are exocytosed. WASH-generated F-actin is required for correct subcellular localization; in WASH complex mutants, and immediately after latrunculin treatment, Mroh1 relocalizes from the cytoplasm to small vesicles. Thus, Mroh1 is involved in a late and hitherto undefined actin-dependent step in exocytosis.
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Affiliation(s)
- Peter A Thomason
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Jason S King
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Robert H Insall
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
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Burgess SG, Bayliss R, Pfuhl M. Solution NMR assignment of the cryptic sixth TOG domain of mini spindles. Biomol NMR Assign 2015; 9:411-413. [PMID: 25971232 DOI: 10.1007/s12104-015-9620-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 05/07/2015] [Indexed: 06/04/2023]
Abstract
TOG domains contribute to the organisation of microtubules through their ability to bind tubulin. They are found in members of the XMAP215 family of proteins, which act as microtubule polymerases and fulfill important roles in the formation of the mitotic spindle and in the assembly of kinetochore fibres. We recently identified a cryptic TOG domain in the XMAP215 family proteins, chTOG and its Drosophila homologue, mini spindles. This domain is not part of the well-established array of TOG domains involved in tubulin polymerisation. Instead it forms part of a binding site for TACC3 family proteins. This interaction is required for the assembly of kinetochore bridges in a trimeric complex with clathrin. Here we present the first NMR assignment of a sixth TOG domain from mini spindles as a first step to elucidate its structure and function.
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Affiliation(s)
- Selena G Burgess
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester, LE1 9HN, UK
- Cancer Research UK Leicester Centre, Lancaster Road, Leicester, LE1 9HN, UK
| | - Richard Bayliss
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester, LE1 9HN, UK
- Cancer Research UK Leicester Centre, Lancaster Road, Leicester, LE1 9HN, UK
| | - Mark Pfuhl
- Cardiovascular and Randall Division, King's College London, Guy's Campus, London, SE1 1UL, UK.
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Monecke T, Dickmanns A, Ficner R. Allosteric control of the exportin CRM1 unraveled by crystal structure analysis. FEBS J 2014; 281:4179-94. [PMID: 24823279 PMCID: PMC4231977 DOI: 10.1111/febs.12842] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/02/2014] [Accepted: 05/12/2014] [Indexed: 01/07/2023]
Abstract
Nucleocytoplasmic trafficking in eukaryotic cells is a highly regulated and coordinated process which involves an increasing variety of soluble nuclear transport receptors. Generally, transport receptors specifically bind their cargo and facilitate its transition through nuclear pore complexes, aqueous channels connecting the two compartments. Directionality of such transport events by receptors of the importin β superfamily requires the interaction with the small GTPase Ras-related nuclear antigen (Ran). While importins need RanGTP to release their cargo in the nucleus and thus to terminate import, exportins recruit cargo in the RanGTP-bound state. The exportin chromosome region maintenance 1 (CRM1) is a highly versatile transport receptor that exports a plethora of different protein and RNP cargoes. Moreover, binding of RanGTP and of cargo to CRM1 are highly cooperative events despite the fact that cargo and RanGTP do not interact directly in crystal structures of assembled export complexes. Integrative approaches have recently unraveled the individual steps of the CRM1 transport cycle at a structural level and explained how the HEAT-repeat architecture of CRM1 provides a framework for the key elements to mediate allosteric interactions with RanGTP, Ran binding proteins and cargo. Moreover, during the last decade, CRM1 has become a more and more appreciated target for anti-cancer drugs. Hence, detailed understanding of the flexibility, the regulatory features and the positive binding cooperativity between CRM1, Ran and cargo is a prerequisite for the development of highly effective drugs. Here we review recent structural advances in the characterization of CRM1 and CRM1-containing complexes with a special emphasis on X-ray crystallographic studies.
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Affiliation(s)
- Thomas Monecke
- Abteilung für Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August-Universität Göttingen, Germany
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Tsai JY, Chu CC, Yeh YH, Chen LJ, Li HM, Hsiao CD. Structural characterizations of the chloroplast translocon protein Tic110. Plant J 2013; 75:847-57. [PMID: 23711301 PMCID: PMC3823011 DOI: 10.1111/tpj.12249] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 05/07/2013] [Accepted: 05/14/2013] [Indexed: 05/07/2023]
Abstract
Tic110 is a major component of the chloroplast protein import translocon. Two functions with mutually exclusive structures have been proposed for Tic110: a protein-conducting channel with six transmembrane domains and a scaffold with two N-terminal transmembrane domains followed by a large soluble domain for binding transit peptides and other stromal translocon components. To investigate the structure of Tic110, Tic110 from Cyanidioschyzon merolae (CmTic110) was characterized. We constructed three fragments, CmTic110A , CmTic110B and CmTic110C , with increasing N-terminal truncations, to perform small-angle X-ray scattering (SAXS) and X-ray crystallography analyses and Dali structural comparison. Here we report the molecular envelope of CmTic110B and CmTic110C determined by SAXS, and the crystal structure of CmTic110C at 4.2 Å. Our data indicate that the C-terminal half of CmTic110 possesses a rod-shaped helix-repeat structure that is too flattened and elongated to be a channel. The structure is most similar to the HEAT-repeat motif that functions as scaffolds for protein-protein interactions.
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Wang H, Nong Y, Bazan F, Greengard P, Flajolet M. Norbin: A promising central nervous system regulator. Commun Integr Biol 2010; 3:487-90. [PMID: 21331221 DOI: 10.4161/cib.3.6.12844] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 06/29/2010] [Indexed: 11/19/2022] Open
Abstract
Norbin, a neurite-outgrowth promoting protein, has been found to interact with and regulate several membrane proteins, including metabotropic glutamate receptor 5 (mGluR5). The disruption of both Norbin alleles leads to early embryonic death between 3.5 and 6.5 day post coitus.1 Forebrain specific Norbin knockout (KO) mice are defective in synaptic plasticity,2 an interesting feature considering that Norbin was initially discovered in the context of chemical-induced long term potentiation (LTP),3 a form of synaptic plasticity extensively studied in the context of learning and memory.4 The behavioral phenotypes associated with Norbin conditional KO suggest reduced mGluR5 function. Because of its fundamental functions, Norbin is emerging as a key neuronal regulator. The aim of the present review is to summarize current knowledge about Norbin while emphasizing its role in the nervous system.
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Affiliation(s)
- Hong Wang
- Laboratory of Molecular and Cellular Neuroscience; The Rockefeller University; New York, NY USA
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