1
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Saini S, Goel K, Ghosh S, Das A, Saraogi I. Effects of PNA Sequence and Target Site Selection on Function of a 4.5S Non-Coding RNA. Chembiochem 2024:e202400029. [PMID: 38595046 DOI: 10.1002/cbic.202400029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 04/09/2024] [Accepted: 04/09/2024] [Indexed: 04/11/2024]
Abstract
Peptide nucleic acid (PNA) based antisense strategy is a promising therapeutic approach to specifically inhibit target gene expression. However, unlike protein coding genes, identification of an ideal PNA binding site for non-coding RNA is not straightforward. Here, we compare the inhibitory activities of PNA molecules that bind a non-coding 4.5S RNA called SRP RNA, a key component of the bacterial signal recognition particle (SRP). A 9-mer PNA (PNA9) complementary to the tetraloop region of the RNA was more potent in inhibiting its interaction with the SRP protein, compared to an 8-mer PNA (PNA8) targeting a stem-loop. PNA9, which contained a homo-pyrimidine sequence could form a triplex with the complementary stretch of RNA in vitro as confirmed using a fluorescent derivative of PNA9 (F-PNA13). The RNA-PNA complex formation resulted in inhibition of SRP function with PNA9 and F-PNA13, but not PNA8 highlighting the importance of target site selection. Surprisingly, F-PNA13 which was more potent in inhibiting SRP function in vitro, showed weaker antibacterial activity compared to PNA9 likely due to poor cell penetration of the longer PNA. Our results underscore the importance of suitable target site selection and optimum PNA length to develop better antisense molecules against non-coding RNA.
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Affiliation(s)
- Snehlata Saini
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Khushboo Goel
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Sudipta Ghosh
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Anirban Das
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Ishu Saraogi
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
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2
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Muthukumar G, Stevens TA, Inglis AJ, Esantsi TK, Saunders RA, Schulte F, Voorhees RM, Guna A, Weissman JS. Triaging of α-helical proteins to the mitochondrial outer membrane by distinct chaperone machinery based on substrate topology. Mol Cell 2024; 84:1101-1119.e9. [PMID: 38428433 DOI: 10.1016/j.molcel.2024.01.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/08/2023] [Accepted: 01/31/2024] [Indexed: 03/03/2024]
Abstract
Mitochondrial outer membrane ⍺-helical proteins play critical roles in mitochondrial-cytoplasmic communication, but the rules governing the targeting and insertion of these biophysically diverse proteins remain unknown. Here, we first defined the complement of required mammalian biogenesis machinery through genome-wide CRISPRi screens using topologically distinct membrane proteins. Systematic analysis of nine identified factors across 21 diverse ⍺-helical substrates reveals that these components are organized into distinct targeting pathways that act on substrates based on their topology. NAC is required for the efficient targeting of polytopic proteins, whereas signal-anchored proteins require TTC1, a cytosolic chaperone that physically engages substrates. Biochemical and mutational studies reveal that TTC1 employs a conserved TPR domain and a hydrophobic groove in its C-terminal domain to support substrate solubilization and insertion into mitochondria. Thus, the targeting of diverse mitochondrial membrane proteins is achieved through topological triaging in the cytosol using principles with similarities to ER membrane protein biogenesis systems.
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Affiliation(s)
- Gayathri Muthukumar
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Taylor A Stevens
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alison J Inglis
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Theodore K Esantsi
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Reuben A Saunders
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Tetrad Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabian Schulte
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Rebecca M Voorhees
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alina Guna
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA.
| | - Jonathan S Weissman
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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3
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Julien S, Challier I, Malleter M, Jouen F, Drouot L, Boyer O. Immune-Mediated Necrotizing Myopathy (IMNM): A Story of Antibodies. Antibodies (Basel) 2024; 13:12. [PMID: 38390873 PMCID: PMC10885118 DOI: 10.3390/antib13010012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 01/10/2024] [Accepted: 02/02/2024] [Indexed: 02/24/2024] Open
Abstract
Immune-mediated necrotizing myopathy (IMNM) is a rare and severe disease that corresponds to a specific entity of idiopathic inflammatory myopathy. Patients with IMNM suffer from proximal muscle weakness, and present high levels of creatine kinase and necrotic myofibers. Anti-Signal Recognition Particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase autoantibodies (HMGCR) have recently been identified in two thirds of patients with IMNM and are used as a hallmark of the disease. In this review, we provide a detailed description of these antibodies and the tests used to detect them in the serum of patients. Based on in vitro studies and mouse models of IMNM, we discuss the role of autoantibodies in the pathogenesis of the disease. Finally, in the light of the latest knowledge, we conclude with a review of recent therapeutic approaches in IMNM.
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Affiliation(s)
- Sarah Julien
- INSERM U1234, PAn'THER FOCIS Center of Excellence, Université de Rouen, F-76000 Rouen, France
| | - Inès Challier
- Department of Pharmacy, CHU Rouen, F-76000 Rouen, France
| | - Marine Malleter
- INSERM U1234, PAn'THER FOCIS Center of Excellence, Université de Rouen, F-76000 Rouen, France
| | - Fabienne Jouen
- INSERM U1234, PAn'THER FOCIS Center of Excellence, Université de Rouen, F-76000 Rouen, France
- Department of Immunology and Biotherapy, CHU Rouen, F-76000 Rouen, France
| | - Laurent Drouot
- INSERM U1234, PAn'THER FOCIS Center of Excellence, Université de Rouen, F-76000 Rouen, France
| | - Olivier Boyer
- INSERM U1234, PAn'THER FOCIS Center of Excellence, Université de Rouen, F-76000 Rouen, France
- Department of Immunology and Biotherapy, CHU Rouen, F-76000 Rouen, France
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4
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Gamerdinger M, Deuerling E. Cotranslational sorting and processing of newly synthesized proteins in eukaryotes. Trends Biochem Sci 2024; 49:105-118. [PMID: 37919225 DOI: 10.1016/j.tibs.2023.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/28/2023] [Accepted: 10/06/2023] [Indexed: 11/04/2023]
Abstract
Ribosomes interact with a variety of different protein biogenesis factors that guide newly synthesized proteins to their native 3D shapes and cellular localization. Depending on the type of translated substrate, a distinct set of cotranslational factors must interact with the ribosome in a timely and coordinated manner to ensure proper protein biogenesis. While cytonuclear proteins require cotranslational maturation and folding factors, secretory proteins must be maintained in an unfolded state and processed cotranslationally by transport and membrane translocation factors. Here we explore the specific cotranslational processing steps for cytonuclear, secretory, and membrane proteins in eukaryotes and then discuss how the nascent polypeptide-associated complex (NAC) cotranslationally sorts these proteins into the correct protein biogenesis pathway.
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Affiliation(s)
- Martin Gamerdinger
- Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.
| | - Elke Deuerling
- Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.
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5
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Badelt S, Lorenz R. A Guide to Computational Cotranscriptional Folding Featuring the SRP RNA. Methods Mol Biol 2024; 2726:315-346. [PMID: 38780737 DOI: 10.1007/978-1-0716-3519-3_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Although RNA molecules are synthesized via transcription, little is known about the general impact of cotranscriptional folding in vivo. We present different computational approaches for the simulation of changing structure ensembles during transcription, including interpretations with respect to experimental data from literature. Specifically, we analyze different mutations of the E. coli SRP RNA, which has been studied comparatively well in previous literature, yet the details of which specific metastable structures form as well as when they form are still under debate. Here, we combine thermodynamic and kinetic, deterministic, and stochastic models with automated and visual inspection of those systems to derive the most likely scenario of which substructures form at which point during transcription. The simulations do not only provide explanations for present experimental observations but also suggest previously unnoticed conformations that may be verified through future experimental studies.
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Affiliation(s)
- Stefan Badelt
- Department of Theoretical Chemistry, University of Vienna, Vienna, Austria.
| | - Ronny Lorenz
- Department of Theoretical Chemistry, University of Vienna, Vienna, Austria
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6
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Pei C, Todorov P, Cao M, Kong Q, Isachenko E, Rahimi G, Mallmann-Gottschalk N, Uribe P, Sanchez R, Isachenko V. Comparative Transcriptomic Analyses for the Optimization of Thawing Regimes during Conventional Cryopreservation of Mature and Immature Human Testicular Tissue. Int J Mol Sci 2023; 25:214. [PMID: 38203385 PMCID: PMC10778995 DOI: 10.3390/ijms25010214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 12/15/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
Cryopreservation of human testicular tissue, as a key element of anticancer therapy, includes the following stages: saturation with cryoprotectants, freezing, thawing, and removal of cryoprotectants. According to the point of view existing in "classical" cryobiology, the thawing mode is the most important consideration in the entire process of cryopreservation of any type of cells, including cells of testicular tissue. The existing postulate in cryobiology states that any frozen types of cells must be thawed as quickly as possible. The technologically maximum possible thawing temperature is 100 °C, which is used in our technology for the cryopreservation of testicular tissue. However, there are other points of view on the rate of cell thawing, according to how thawing should be carried out at physiological temperatures. In fact, there are morphological and functional differences between immature (from prepubertal patients) and mature testicular tissue. Accordingly, the question of the influence of thawing temperature on both types of tissues is relevant. The purpose of this study is to explore the transcriptomic differences of cryopreserved mature and immature testicular tissue subjected to different thawing methods by RNA sequencing. Collected and frozen testicular tissue samples were divided into four groups: quickly (in boiling water at 100 °C) thawed cryopreserved mature testicular tissue (group 1), slowly (by a physiological temperature of 37 °C) thawed mature testicular tissue (group 2), quickly thawed immature testicular tissue (group 3), and slowly thawed immature testicular tissue (group 4). Transcriptomic differences were assessed using differentially expressed genes (DEG), the Kyoto Encyclopedia of Genes and Genomes (KEGG), gene ontology (GO), and protein-protein interaction (PPI) analyses. No fundamental differences in the quality of cells of mature and immature testicular tissue after cryopreservation were found. Generally, thawing of mature and immature testicular tissue was more effective at 100 °C. The greatest difference in the intensity of gene expression was observed in ribosomes of cells thawed at 100 °C in comparison with cells thawed at 37 °C. In conclusion, an elevated speed of thawing is beneficial for frozen testicular tissue.
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Affiliation(s)
- Cheng Pei
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
| | - Plamen Todorov
- Institute of Biology and Immunology of Reproduction of Bulgarian Academy of Sciences (BAS), 1113 Sofia, Bulgaria;
| | - Mengyang Cao
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
| | - Qingduo Kong
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
| | - Evgenia Isachenko
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
| | - Gohar Rahimi
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
- Medizinisches Versorgungszentrum AMEDES für IVF- und Pränatalmedizin in Köln GmbH, 50968 Cologne, Germany
| | - Nina Mallmann-Gottschalk
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
| | - Pamela Uribe
- Center of Excellence in Translational Medicine, Scientific and Technological Bioresource Nucleus (CEMT-BIOREN), Temuco 4810296, Chile; (P.U.); (R.S.)
- Department of Internal Medicine, Faculty of Medicine, Universidad de la Frontera, Temuco 4811230, Chile
| | - Raul Sanchez
- Center of Excellence in Translational Medicine, Scientific and Technological Bioresource Nucleus (CEMT-BIOREN), Temuco 4810296, Chile; (P.U.); (R.S.)
- Department of Preclinical Sciences, Faculty of Medicine, Universidad de la Frontera, Temuco 4811230, Chile
| | - Volodimir Isachenko
- Department of Obstetrics and Gynecology, Medical Faculty, Cologne University, 50931 Cologne, Germany; (C.P.); (Q.K.); (E.I.); (N.M.-G.)
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7
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Child JR, Hofler AC, Chen Q, Yang BH, Kristofich J, Zheng T, Hannigan MM, Elles AL, Reid DW, Nicchitta CV. Examining SRP pathway function in mRNA localization to the endoplasmic reticulum. RNA (NEW YORK, N.Y.) 2023; 29:1703-1724. [PMID: 37643813 PMCID: PMC10578483 DOI: 10.1261/rna.079643.123] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Accepted: 07/17/2023] [Indexed: 08/31/2023]
Abstract
Signal recognition particle (SRP) pathway function in protein translocation across the endoplasmic reticulum (ER) is well established; its role in RNA localization to the ER remains, however, unclear. In current models, mRNAs undergo translation- and SRP-dependent trafficking to the ER, with ER localization mediated via interactions between SRP-bound translating ribosomes and the ER-resident SRP receptor (SR), a heterodimeric complex comprising SRA, the SRP-binding subunit, and SRB, an integral membrane ER protein. To study SRP pathway function in RNA localization, SR knockout (KO) mammalian cell lines were generated and the consequences of SR KO on steady-state and dynamic mRNA localization examined. CRISPR/Cas9-mediated SRPRB KO resulted in profound destabilization of SRA. Pairing siRNA silencing of SRPRA in SRPRB KO cells yielded viable SR KO cells. Steady-state mRNA compositions and ER-localization patterns in parental and SR KO cells were determined by cell fractionation and deep sequencing. Notably, steady-state cytosol and ER mRNA compositions and partitioning patterns were largely unaltered by loss of SR expression. To examine SRP pathway function in RNA localization dynamics, the subcellular trafficking itineraries of newly exported mRNAs were determined by 4-thiouridine (4SU) pulse-labeling/4SU-seq/cell fractionation. Newly exported mRNAs were distinguished by high ER enrichment, with ER localization being SR-independent. Intriguingly, under conditions of translation initiation inhibition, the ER was the default localization site for all newly exported mRNAs. These data demonstrate that mRNA localization to the ER can be uncoupled from the SRP pathway function and reopen questions regarding the mechanism of RNA localization to the ER.
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Affiliation(s)
- Jessica R Child
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Alex C Hofler
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Qiang Chen
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Brenda H Yang
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - JohnCarlo Kristofich
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Tianli Zheng
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Molly M Hannigan
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Andrew L Elles
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - David W Reid
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Christopher V Nicchitta
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
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8
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Weigert N, Schweiger AL, Gross J, Matthes M, Corbacioglu S, Sommer G, Heise T. Detection of a 7SL RNA-derived small non-coding RNA using Molecular Beacons in vitro and in cells. Biol Chem 2023; 404:1123-1136. [PMID: 37632732 DOI: 10.1515/hsz-2023-0185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 08/11/2023] [Indexed: 08/28/2023]
Abstract
Small non-coding RNAs (sncRNA) are involved in many steps of the gene expression cascade and regulate processing and expression of mRNAs by the formation of ribonucleoprotein complexes (RNP) such as the RNA-induced silencing complex (RISC). By analyzing small RNA Seq data sets, we identified a sncRNA annotated as piR-hsa-1254, which is likely derived from the 3'-end of 7SL RNA2 (RN7SL2), herein referred to as snc7SL RNA. The 7SL RNA is an abundant long non-coding RNA polymerase III transcript and serves as structural component of the cytoplasmic signal recognition particle (SRP). To evaluate a potential functional role of snc7SL RNA, we aimed to define its cellular localization by live cell imaging. Therefore, a Molecular Beacon (MB)-based method was established to compare the subcellular localization of snc7SL RNA with its precursor 7SL RNA. We designed and characterized several MBs in vitro and tested those by live cell fluorescence microscopy. Using a multiplex approach, we show that 7SL RNA localizes mainly to the endoplasmic reticulum (ER), as expected for the SRP, whereas snc7SL RNA predominately localizes to the nucleus. This finding suggests a fundamentally different function of 7SL RNA and its derivate snc7SL RNA.
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Affiliation(s)
- Nina Weigert
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
| | - Anna-Lena Schweiger
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
| | - Jonas Gross
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
| | - Marie Matthes
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
| | - Selim Corbacioglu
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
| | - Gunhild Sommer
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
| | - Tilman Heise
- Department for Pediatric Hematology, Oncology and Stem Cell Transplantation, University Hospital Regensburg, Franz-Josef-Strauß Allee 11, D-93053 Regensburg, Germany
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9
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Zaragoza-Gómez A, García-Caffarel E, Cruz-Zamora Y, González J, Anaya-Muñoz VH, Cruz-García F, Juárez-Díaz JA. The Nβ motif of NaTrxh directs secretion as an endoplasmic reticulum transit peptide and variations might result in different cellular targeting. PLoS One 2023; 18:e0287087. [PMID: 37824466 PMCID: PMC10569557 DOI: 10.1371/journal.pone.0287087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Accepted: 09/29/2023] [Indexed: 10/14/2023] Open
Abstract
Soluble secretory proteins with a signal peptide reach the extracellular space through the endoplasmic reticulum-Golgi conventional pathway. During translation, the signal peptide is recognised by the signal recognition particle and results in a co-translational translocation to the endoplasmic reticulum to continue the secretory pathway. However, soluble secretory proteins lacking a signal peptide are also abundant, and several unconventional (endoplasmic reticulum/Golgi independent) pathways have been proposed and some demonstrated. This work describes new features of the secretion signal called Nβ, originally identified in NaTrxh, a plant extracellular thioredoxin, that does not possess an orthodox signal peptide. We provide evidence that other proteins, including thioredoxins type h, with similar sequences are also signal peptide-lacking secretory proteins. To be a secretion signal, positions 5, 8 and 9 must contain neutral residues in plant proteins-a negative residue in position 8 is suggested in animal proteins-to maintain the Nβ motif negatively charged and a hydrophilic profile. Moreover, our results suggest that the NaTrxh translocation to the endoplasmic reticulum occurs as a post-translational event. Finally, the Nβ motif sequence at the N- or C-terminus could be a feature that may help to predict protein localisation, mainly in plant and animal proteins.
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Affiliation(s)
- Andre Zaragoza-Gómez
- Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, UNAM, Ciudad de Mexico, México
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Ciudad de Mexico, México
| | - Emilio García-Caffarel
- Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, UNAM, Ciudad de Mexico, México
| | - Yuridia Cruz-Zamora
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, UNAM, Ciudad de Mexico, México
| | - James González
- Departamento de Biología Celular, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, UNAM, Ciudad de Mexico, México
| | - Víctor Hugo Anaya-Muñoz
- Escuela Nacional Estudios Superiores unidad Morelia, Universidad Nacional Autónoma de México, Campus Morelia, Morelia, Michoacán, México
| | - Felipe Cruz-García
- Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, UNAM, Ciudad de Mexico, México
| | - Javier Andrés Juárez-Díaz
- Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, UNAM, Ciudad de Mexico, México
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10
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Muthukumar G, Stevens TA, Inglis AJ, Esantsi TK, Saunders RA, Schulte F, Voorhees RM, Guna A, Weissman JS. Triaging of α-helical proteins to the mitochondrial outer membrane by distinct chaperone machinery based on substrate topology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.16.553624. [PMID: 37645817 PMCID: PMC10462106 DOI: 10.1101/2023.08.16.553624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Mitochondrial outer membrane α-helical proteins play critical roles in mitochondrial-cytoplasmic communication, but the rules governing the targeting and insertion of these biophysically diverse substrates remain unknown. Here, we first defined the complement of required mammalian biogenesis machinery through genome-wide CRISPRi screens using topologically distinct membrane proteins. Systematic analysis of nine identified factors across 21 diverse α-helical substrates reveals that these components are organized into distinct targeting pathways which act on substrates based on their topology. NAC is required for efficient targeting of polytopic proteins whereas signal-anchored proteins require TTC1, a novel cytosolic chaperone which physically engages substrates. Biochemical and mutational studies reveal that TTC1 employs a conserved TPR domain and a hydrophobic groove in its C-terminal domain to support substrate solubilization and insertion into mitochondria. Thus, targeting of diverse mitochondrial membrane proteins is achieved through topological triaging in the cytosol using principles with similarities to ER membrane protein biogenesis systems.
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Affiliation(s)
- Gayathri Muthukumar
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Taylor A. Stevens
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alison J. Inglis
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Theodore K. Esantsi
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Reuben A. Saunders
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- Tetrad Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabian Schulte
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Rebecca M. Voorhees
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alina Guna
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Jonathan S. Weissman
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute Technology, Cambridge 02142, MA
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11
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Höpfler M, Hegde RS. Control of mRNA fate by its encoded nascent polypeptide. Mol Cell 2023; 83:2840-2855. [PMID: 37595554 PMCID: PMC10501990 DOI: 10.1016/j.molcel.2023.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 07/03/2023] [Accepted: 07/11/2023] [Indexed: 08/20/2023]
Abstract
Cells tightly regulate mRNA processing, localization, and stability to ensure accurate gene expression in diverse cellular states and conditions. Most of these regulatory steps have traditionally been thought to occur before translation by the action of RNA-binding proteins. Several recent discoveries highlight multiple co-translational mechanisms that modulate mRNA translation, localization, processing, and stability. These mechanisms operate by recognition of the nascent protein, which is necessarily coupled to its encoding mRNA during translation. Hence, the distinctive sequence or structure of a particular nascent chain can recruit recognition factors with privileged access to the corresponding mRNA in an otherwise crowded cellular environment. Here, we draw on both well-established and recent examples to provide a conceptual framework for how cells exploit nascent protein recognition to direct mRNA fate. These mechanisms allow cells to dynamically and specifically regulate their transcriptomes in response to changes in cellular states to maintain protein homeostasis.
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12
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Nguyen T, Mills JC, Cho CJ. The coordinated management of ribosome and translation during injury and regeneration. Front Cell Dev Biol 2023; 11:1186638. [PMID: 37427381 PMCID: PMC10325863 DOI: 10.3389/fcell.2023.1186638] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 06/06/2023] [Indexed: 07/11/2023] Open
Abstract
Diverse acute and chronic injuries induce damage responses in the gastrointestinal (GI) system, and numerous cell types in the gastrointestinal tract demonstrate remarkable resilience, adaptability, and regenerative capacity in response to stress. Metaplasias, such as columnar and secretory cell metaplasia, are well-known adaptations that these cells make, the majority of which are epidemiologically associated with an elevated cancer risk. On a number of fronts, it is now being investigated how cells respond to injury at the tissue level, where diverse cell types that differ in proliferation capacity and differentiation state cooperate and compete with one another to participate in regeneration. In addition, the cascades or series of molecular responses that cells show are just beginning to be understood. Notably, the ribosome, a ribonucleoprotein complex that is essential for translation on the endoplasmic reticulum (ER) and in the cytoplasm, is recognized as the central organelle during this process. The highly regulated management of ribosomes as key translational machinery, and their platform, rough endoplasmic reticulum, are not only essential for maintaining differentiated cell identity, but also for achieving successful cell regeneration after injury. This review will cover in depth how ribosomes, the endoplasmic reticulum, and translation are regulated and managed in response to injury (e.g., paligenosis), as well as why this is essential for the proper adaptation of a cell to stress. For this, we will first discuss how multiple gastrointestinal organs respond to stress through metaplasia. Next, we will cover how ribosomes are generated, maintained, and degraded, in addition to the factors that govern translation. Finally, we will investigate how ribosomes and translation machinery are dynamically regulated in response to injury. Our increased understanding of this overlooked cell fate decision mechanism will facilitate the discovery of novel therapeutic targets for gastrointestinal tract tumors, focusing on ribosomes and translation machinery.
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Affiliation(s)
- Thanh Nguyen
- Department of Medicine, Baylor College of Medicine, Houston, TX, United States
| | - Jason C. Mills
- Department of Medicine, Baylor College of Medicine, Houston, TX, United States
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, United States
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, United States
| | - Charles J. Cho
- Department of Medicine, Baylor College of Medicine, Houston, TX, United States
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13
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Nguyen NH, Brodsky JL. The cellular pathways that maintain the quality control and transport of diverse potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194908. [PMID: 36638864 PMCID: PMC9908860 DOI: 10.1016/j.bbagrm.2023.194908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
Potassium channels are multi-subunit transmembrane proteins that permit the selective passage of potassium and play fundamental roles in physiological processes, such as action potentials in the nervous system and organismal salt and water homeostasis, which is mediated by the kidney. Like all ion channels, newly translated potassium channels enter the endoplasmic reticulum (ER) and undergo the error-prone process of acquiring post-translational modifications, folding into their native conformations, assembling with other subunits, and trafficking through the secretory pathway to reach their final destinations, most commonly the plasma membrane. Disruptions in these processes can result in detrimental consequences, including various human diseases. Thus, multiple quality control checkpoints evolved to guide potassium channels through the secretory pathway and clear potentially toxic, aggregation-prone misfolded species. We will summarize current knowledge on the mechanisms underlying potassium channel quality control in the secretory pathway, highlight diseases associated with channel misfolding, and suggest potential therapeutic routes.
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Affiliation(s)
- Nga H Nguyen
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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14
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Heo P, Culver JA, Miao J, Pincet F, Mariappan M. The Get1/2 insertase forms a channel to mediate the insertion of tail-anchored proteins into the ER. Cell Rep 2023; 42:111921. [PMID: 36640319 PMCID: PMC9932932 DOI: 10.1016/j.celrep.2022.111921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 11/07/2022] [Accepted: 12/13/2022] [Indexed: 12/29/2022] Open
Abstract
Tail-anchored (TA) proteins contain a single C-terminal transmembrane domain (TMD) that is captured by the cytosolic Get3 in yeast (TRC40 in humans). Get3 delivers TA proteins to the Get1/2 complex for insertion into the endoplasmic reticulum (ER) membrane. How Get1/2 mediates insertion of TMDs of TA proteins into the membrane is poorly understood. Using bulk fluorescence and microfluidics assays, we show that Get1/2 forms an aqueous channel in reconstituted bilayers. We estimate the channel diameter to be ∼2.5 nm wide, corresponding to the circumference of two Get1/2 complexes. We find that the Get3 binding can seal the Get1/2 channel, which dynamically opens and closes. Our mutation analysis further shows that the Get1/2 channel activity is required to release TA proteins from Get3 for insertion into the membrane. Hence, we propose that the Get1/2 channel functions as an insertase for insertion of TMDs and as a translocase for translocation of C-terminal hydrophilic segments.
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Affiliation(s)
- Paul Heo
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France; Institute of Psychiatry and Neuroscience of Paris, INSERM U1266, 75014 Paris, France.
| | - Jacob A. Culver
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA,Nanobiology Institute, Yale University West Campus, West Haven, CT 06516, USA
| | - Jennifer Miao
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA,Nanobiology Institute, Yale University West Campus, West Haven, CT 06516, USA
| | - Frederic Pincet
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France.
| | - Malaiyalam Mariappan
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA; Nanobiology Institute, Yale University West Campus, West Haven, CT 06516, USA.
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15
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Qiu R, Wang Z, Wei X, Sui H, Jiang Z, Yu XF. The pathogenesis of anti-signal recognition particle necrotizing myopathy: A Review. Biomed Pharmacother 2022; 156:113936. [DOI: 10.1016/j.biopha.2022.113936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/22/2022] [Accepted: 10/26/2022] [Indexed: 11/06/2022] Open
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16
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Winkenbach LP, Parker DM, Williams RTP, Nishimura EO. The ERM-1 membrane-binding domain directs erm-1 mRNA localization to the plasma membrane in the C. elegans embryo. Development 2022; 149:279335. [PMID: 36314842 PMCID: PMC9793419 DOI: 10.1242/dev.200930] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022]
Abstract
mRNA localization and transport are integral in regulating gene expression. In Caenorhabditis elegans embryos, the maternally inherited mRNA erm-1 (Ezrin/Radixin/Moesin) becomes concentrated in anterior blastomeres. erm-1 mRNA localizes within those blastomeres to the plasma membrane where the essential ERM-1 protein, a membrane-actin linker, is also found. We demonstrate that the localization of erm-1 mRNA to the plasma membrane is translation dependent and requires its encoded N-terminal, membrane-binding (FERM) domain. By perturbing translation through multiple methods, we found that erm-1 mRNA localization at the plasma membrane persisted only if the nascent peptide remained in complex with the translating mRNA. Indeed, re-coding the erm-1 mRNA coding sequence while preserving the encoded amino acid sequence did not disrupt erm-1 mRNA localization, corroborating that the information directing mRNA localization resides within its membrane-binding protein domain. A single-molecule inexpensive fluorescence in situ hybridization screen of 17 genes encoding similar membrane-binding domains identified three plasma membrane-localized mRNAs in the early embryo. Ten additional transcripts showed potential membrane localization later in development. These findings point to a translation-dependent pathway for localization of mRNAs encoding membrane-associated proteins.
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Affiliation(s)
- Lindsay P. Winkenbach
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Dylan M. Parker
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA,Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80303, USA
| | - Robert T. P. Williams
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Erin Osborne Nishimura
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA,Author for correspondence ()
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17
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Schönemann AM, Beiras R, Diz AP. Widespread alterations upon exposure to the estrogenic endocrine disruptor ethinyl estradiol in the liver proteome of the marine male fish Cyprinodon variegatus. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 248:106189. [PMID: 35537357 DOI: 10.1016/j.aquatox.2022.106189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 04/18/2022] [Accepted: 05/02/2022] [Indexed: 06/14/2023]
Abstract
Quantitative proteomic changes in the liver of adult males of Sheepshead minnow (Cyprinodon variegatus) upon exposure to ethinyl estradiol (EE2) were assessed to provide an advanced understanding of the metabolic pathways affected by estrogenic endocrine disruption in marine fish, and to identify potential novel molecular biomarkers for the environmental exposure to estrogens. From a total of 3188 identified protein groups (hereafter proteins), 463 showed a statistically significant difference in their abundance between EE2 treatment and solvent control samples. The most affected biological processes upon EE2 exposure were related to ribosomal biogenesis, protein synthesis and transport of nascent proteins to endoplasmic reticulum, and nuclear mRNA catabolism. Within the group of upregulated proteins, a subset of 14 proteins, involved in egg production (Vitellogenin, Zona Pellucida), peptidase activity (Cathepsine E, peptidase S1, Serine/threonine-protein kinase PRP4 homolog, Isoaspartyl peptidase and Whey acidic protein), and nucleic acid binding (Poly [ADP-ribose] polymerase 14) were significantly upregulated with fold-change values higher than 3. In contrast, Collagen alpha-2, involved in the process of response to steroid hormones, among others, was significantly downregulated (fold change = 0.2). This pattern of alterations in the liver proteome of adult males of C. variegatus can be used to identify promising novel biomarkers for the characterization of exposure of marine fish to estrogens. The Whey acidic protein-like showed the highest upregulation in EE2-exposed individuals (21-fold over controls), suggesting the utility of abundance levels of this protein in male liver as a novel biomarker of xenoestrogen exposure.
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Affiliation(s)
- Alexandre M Schönemann
- Centro de Investigación Mariña da Universidade de Vigo (CIM-UVigo), Vigo, Galicia, Spain; Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain
| | - Ricardo Beiras
- Centro de Investigación Mariña da Universidade de Vigo (CIM-UVigo), Vigo, Galicia, Spain; Department of Ecology and Animal Biology, University of Vigo, Vigo, Galicia, Spain
| | - Angel P Diz
- Centro de Investigación Mariña da Universidade de Vigo (CIM-UVigo), Vigo, Galicia, Spain; Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain.
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18
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Torres M, Hussain H, Dickson AJ. The secretory pathway - the key for unlocking the potential of Chinese hamster ovary cell factories for manufacturing therapeutic proteins. Crit Rev Biotechnol 2022; 43:628-645. [PMID: 35465810 DOI: 10.1080/07388551.2022.2047004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Mammalian cell factories (in particular the CHO cell system) have been crucial in the rise of biopharmaceuticals. Mammalian cells have compartmentalized organelles where intricate networks of proteins manufacture highly sophisticated biopharmaceuticals in a specialized production pipeline - the secretory pathway. In the bioproduction context, the secretory pathway functioning is key for the effectiveness of cell factories to manufacture these life-changing medicines. This review describes the molecular components and events involved in the secretory pathway, and provides a comprehensive summary of the intracellular steps limiting the production of therapeutic proteins as well as the achievements in engineering CHO cell secretory machinery. We also consider antibody-producing plasma cells (so called "professional" secretory cells) to explore the mechanisms underpinning their unique secretory function/features. Such understandings offer the potential to further enhancement of the current CHO cell production platforms for manufacturing next generation of biopharmaceuticals.
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Affiliation(s)
- Mauro Torres
- Manchester Institute of Biotechnology, Faculty of Science and Engineering, University of Manchester, Manchester, UK.,Department of Chemical Engineering and Analytical Science, Biochemical and Bioprocess Engineering Group, University of Manchester, Manchester, UK
| | - Hirra Hussain
- Manchester Institute of Biotechnology, Faculty of Science and Engineering, University of Manchester, Manchester, UK.,Department of Chemical Engineering and Analytical Science, Biochemical and Bioprocess Engineering Group, University of Manchester, Manchester, UK
| | - Alan J Dickson
- Manchester Institute of Biotechnology, Faculty of Science and Engineering, University of Manchester, Manchester, UK.,Department of Chemical Engineering and Analytical Science, Biochemical and Bioprocess Engineering Group, University of Manchester, Manchester, UK
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19
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Fishburn AT, Pham OH, Kenaston MW, Beesabathuni NS, Shah PS. Let's Get Physical: Flavivirus-Host Protein-Protein Interactions in Replication and Pathogenesis. Front Microbiol 2022; 13:847588. [PMID: 35308381 PMCID: PMC8928165 DOI: 10.3389/fmicb.2022.847588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 01/31/2022] [Indexed: 12/23/2022] Open
Abstract
Flaviviruses comprise a genus of viruses that pose a significant burden on human health worldwide. Transmission by both mosquito and tick vectors, and broad host tropism contribute to the presence of flaviviruses globally. Like all viruses, they require utilization of host molecular machinery to facilitate their replication through physical interactions. Their RNA genomes are translated using host ribosomes, synthesizing viral proteins that cooperate with each other and host proteins to reshape the host cell into a factory for virus replication. Thus, dissecting the physical interactions between viral proteins and their host protein targets is essential in our comprehension of how flaviviruses replicate and how they alter host cell behavior. Beyond replication, even single interactions can contribute to immune evasion and pathogenesis, providing potential avenues for therapeutic intervention. Here, we review protein interactions between flavivirus and host proteins that contribute to virus replication, immune evasion, and disease.
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Affiliation(s)
- Adam T Fishburn
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA, United States
| | - Oanh H Pham
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA, United States
| | - Matthew W Kenaston
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA, United States
| | - Nitin S Beesabathuni
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA, United States.,Department of Chemical Engineering, University of California, Davis, Davis, CA, United States
| | - Priya S Shah
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA, United States.,Department of Chemical Engineering, University of California, Davis, Davis, CA, United States
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20
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Peña N, Zhang W, Watkins C, Halucha M, Alshammary H, Hernandez MM, Liu WC, Albrecht RA, Garcia-Sastre A, Simon V, Katanski C, Pan T. Profiling Selective Packaging of Host RNA and Viral RNA Modification in SARS-CoV-2 Viral Preparations. Front Cell Dev Biol 2022; 10:768356. [PMID: 35186917 PMCID: PMC8851031 DOI: 10.3389/fcell.2022.768356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 01/18/2022] [Indexed: 11/24/2022] Open
Abstract
Viruses package host RNAs in their virions which are associated with a range of functions in the viral life cycle. Previous transcriptomic profiling of host RNA packaging mostly focused on retroviruses. Which host RNAs are packaged in other viruses at the transcriptome level has not been thoroughly examined. Here we perform proof-of-concept studies using both small RNA and large RNA sequencing of six different SARS-CoV-2 viral isolates grown on VeroE6 cells to profile host RNAs present in cell free viral preparations and to explore SARS-CoV-2 genomic RNA modifications. We find selective enrichment of specific host transfer RNAs (tRNAs), tRNA fragments and signal recognition particle (SRP) RNA in SARS-CoV-2 viral preparations. Different viral preparations contain the same set of host RNAs, suggesting a common mechanism of packaging. We estimate that a single SARS-CoV-2 particle likely contains up to one SRP RNA and four tRNA molecules. We identify tRNA modification differences between the tRNAs present in viral preparations and those in the uninfected VeroE6 host cells. Furthermore, we find uncharacterized candidate modifications in the SARS-CoV-2 genomic RNA. Our results reveal an under-studied aspect of viral-host interactions that may be explored for viral therapeutics.
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Affiliation(s)
- Noah Peña
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, United States
| | - Wen Zhang
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, United States
| | - Christopher Watkins
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, United States
| | - Mateusz Halucha
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, United States
| | - Hala Alshammary
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Matthew M. Hernandez
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Department of Pathology, Molecular and Cell Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Wen-Chun Liu
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- The Global Health and Emerging Pathogen Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Randy A. Albrecht
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- The Global Health and Emerging Pathogen Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Adolfo Garcia-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Department of Pathology, Molecular and Cell Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- The Global Health and Emerging Pathogen Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Division of Infectious Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Viviana Simon
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Department of Pathology, Molecular and Cell Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- The Global Health and Emerging Pathogen Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Division of Infectious Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Christopher Katanski
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, United States
| | - Tao Pan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, United States
- Committee on Microbiology, University of Chicago, Chicago, IL, United States
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21
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Hegde RS, Keenan RJ. The mechanisms of integral membrane protein biogenesis. Nat Rev Mol Cell Biol 2022; 23:107-124. [PMID: 34556847 DOI: 10.1038/s41580-021-00413-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2021] [Indexed: 02/08/2023]
Abstract
Roughly one quarter of all genes code for integral membrane proteins that are inserted into the plasma membrane of prokaryotes or the endoplasmic reticulum membrane of eukaryotes. Multiple pathways are used for the targeting and insertion of membrane proteins on the basis of their topological and biophysical characteristics. Multipass membrane proteins span the membrane multiple times and face the additional challenges of intramembrane folding. In many cases, integral membrane proteins require assembly with other proteins to form multi-subunit membrane protein complexes. Recent biochemical and structural analyses have provided considerable clarity regarding the molecular basis of membrane protein targeting and insertion, with tantalizing new insights into the poorly understood processes of multipass membrane protein biogenesis and multi-subunit protein complex assembly.
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Affiliation(s)
- Ramanujan S Hegde
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, UK.
| | - Robert J Keenan
- Gordon Center for Integrative Science, The University of Chicago, Chicago, IL, USA.
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22
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Zhang B, Hu X, Li Y, Ni Y, Xue L. Identification of methylation markers for diagnosis of autism spectrum disorder. Metab Brain Dis 2022; 37:219-228. [PMID: 34427843 DOI: 10.1007/s11011-021-00805-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 07/23/2021] [Indexed: 10/20/2022]
Abstract
Autism spectrum disorder (ASD) is a hereditary heterogeneous neurodevelopmental disorder characterized by social and speech dysplasia. We collected the expression profiles of ASD in GSE26415, GSE42133 and GSE123302 from the gene expression omnibus (GEO) database, as well as methylation data of GSE109905. Differentially expressed genes (DEGs) between ASD and controls were obtained by differential expression analysis. Enrichment analysis identified the biological functions and signaling pathways involved by common genes in three groups of DEGs. Protein-protein interaction (PPI) networks were used to identify genes with the highest connectivity as key genes. In addition, we identified methylation markers by associating differentially methylated positions. Key methylation markers were identified using the least absolute shrink and selection operator (LASSO) model. Receiver operating characteristic curves and nomograms were used to identify the diagnostic role of key methylation markers for ASD. A total of 57 common genes were identified in the three groups of DEGs. These genes were mainly enriched in Sphingolipid metabolism and PPAR signaling pathway. In the PPI network, we identified seven key genes with higher connectivity, and used qRT-PCR experiments to verify the expressions. In addition, we identified 31 methylation markers and screened 3 key methylation markers (RUNX2, IMMP2L and MDM2) by LASSO model. Their methylation levels were closely related to the diagnostic effects of ASD. Our analysis identified RUNX2, IMMP2L and MDM2 as possible diagnostic markers for ASD. Identifying different biomarkers and risk genes will contribute to the diagnosis of ASD and the development of new clinical and drug treatments.
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Affiliation(s)
- Bei Zhang
- Department of quality management, The Fourth People's Hospital of Urumqi, Jianquan street, Urumqi, Xinjiang, 830002, China
| | - Xiaoyuan Hu
- Xinjiang Uighur Autonomous Region Center for Disease Control and Prevention, Jianquan street, Tianshan District, Urumqi, Xinjiang, 830001, China
| | - Yuefei Li
- School of Public Health, Xinjiang Medical University, Liyushan Road, Xinshi District, Urumqi, Xinjiang, 830000, China
| | - Yongkang Ni
- School of Public Health, Xinjiang Medical University, Liyushan Road, Xinshi District, Urumqi, Xinjiang, 830000, China
| | - Lin Xue
- Department of quality management, The Fourth People's Hospital of Urumqi, Jianquan street, Urumqi, Xinjiang, 830002, China.
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23
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Whitley P, Grau B, Gumbart JC, Martínez-Gil L, Mingarro I. Folding and Insertion of Transmembrane Helices at the ER. Int J Mol Sci 2021; 22:ijms222312778. [PMID: 34884581 PMCID: PMC8657811 DOI: 10.3390/ijms222312778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 01/16/2023] Open
Abstract
In eukaryotic cells, the endoplasmic reticulum (ER) is the entry point for newly synthesized proteins that are subsequently distributed to organelles of the endomembrane system. Some of these proteins are completely translocated into the lumen of the ER while others integrate stretches of amino acids into the greasy 30 Å wide interior of the ER membrane bilayer. It is generally accepted that to exist in this non-aqueous environment the majority of membrane integrated amino acids are primarily non-polar/hydrophobic and adopt an α-helical conformation. These stretches are typically around 20 amino acids long and are known as transmembrane (TM) helices. In this review, we will consider how transmembrane helices achieve membrane integration. We will address questions such as: Where do the stretches of amino acids fold into a helical conformation? What is/are the route/routes that these stretches take from synthesis at the ribosome to integration through the ER translocon? How do these stretches ‘know’ to integrate and in which orientation? How do marginally hydrophobic stretches of amino acids integrate and survive as transmembrane helices?
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Affiliation(s)
- Paul Whitley
- Department of Biology and Biochemistry, Centre for Regenerative Medicine, University of Bath, Bath BA2 7AY, UK;
| | - Brayan Grau
- Department of Biochemistry and Molecular Biology, Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain; (B.G.); (L.M.-G.)
| | - James C. Gumbart
- School of Physics, School of Chemistry and Biochemistry, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA;
| | - Luis Martínez-Gil
- Department of Biochemistry and Molecular Biology, Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain; (B.G.); (L.M.-G.)
| | - Ismael Mingarro
- Department of Biochemistry and Molecular Biology, Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain; (B.G.); (L.M.-G.)
- Correspondence: ; Tel.: +34-963543796
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Pauwels E, Rutz C, Provinciael B, Stroobants J, Schols D, Hartmann E, Krause E, Stephanowitz H, Schülein R, Vermeire K. A Proteomic Study on the Membrane Protein Fraction of T Cells Confirms High Substrate Selectivity for the ER Translocation Inhibitor Cyclotriazadisulfonamide. Mol Cell Proteomics 2021; 20:100144. [PMID: 34481949 PMCID: PMC8477212 DOI: 10.1016/j.mcpro.2021.100144] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 08/09/2021] [Accepted: 08/30/2021] [Indexed: 11/15/2022] Open
Abstract
Cyclotriazadisulfonamide (CADA) inhibits the cotranslational translocation of type I integral membrane protein human CD4 (huCD4) across the endoplasmic reticulum in a signal peptide (SP)–dependent way. Previously, sortilin was identified as a secondary substrate for CADA but showed reduced CADA sensitivity as compared with huCD4. Here, we performed a quantitative proteomic study on the crude membrane fraction of human T-cells to analyze how many proteins are sensitive to CADA. To screen for these proteins, we employed stable isotope labeling by amino acids in cell culture technique in combination with quantitative MS on CADA-treated human T-lymphoid SUP-T1 cells expressing high levels of huCD4. In line with our previous reports, our current proteomic analysis (data available via ProteomeXchange with identifier PXD027712) demonstrated that only a very small subset of proteins is depleted by CADA. Our data also confirmed that cellular expression of both huCD4 and sortilin are affected by CADA treatment of SUP-T1 cells. Furthermore, three additional targets for CADA are identified, namely, endoplasmic reticulum lectin 1 (ERLEC1), inactive tyrosine-protein kinase 7 (PTK7), and DnaJ homolog subfamily C member 3 (DNAJC3). Western blot and flow cytometry analysis of ERLEC1, PTK7, and DNAJC3 protein expression validated susceptibility of these substrates to CADA, although with varying degrees of sensitivity. Additional cell-free in vitro translation/translocation data demonstrated that the new substrates for CADA carry cleavable SPs that are targets for the cotranslational translocation inhibition exerted by CADA. Thus, our quantitative proteomic analysis demonstrates that ERLEC1, PTK7, and DNAJC3 are validated additional substrates of CADA; however, huCD4 remains the most sensitive integral membrane protein for the endoplasmic reticulum translocation inhibitor CADA. Furthermore, to our knowledge, CADA is the first compound that specifically interferes with only a very small subset of SPs and does not affect signal anchor sequences. About 3007 proteins quantified in SILAC/MS study on CD4+ T-cells treated with CADA. Three new targets for CADA were identified: ERLEC1, PTK7, and DNAJC3. All CADA substrates carry cleavable signal peptides for translocation into ER. huCD4 remains the most sensitive substrate for the ER translocation inhibitor CADA.
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Affiliation(s)
- Eva Pauwels
- Laboratory of Virology and Chemotherapy, KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Leuven, Belgium
| | - Claudia Rutz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Becky Provinciael
- Laboratory of Virology and Chemotherapy, KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Leuven, Belgium
| | - Joren Stroobants
- Laboratory of Virology and Chemotherapy, KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Leuven, Belgium
| | - Dominique Schols
- Laboratory of Virology and Chemotherapy, KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Leuven, Belgium
| | - Enno Hartmann
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck, Germany
| | - Eberhard Krause
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Heike Stephanowitz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Ralf Schülein
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Kurt Vermeire
- Laboratory of Virology and Chemotherapy, KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Leuven, Belgium.
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25
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Blatnik AJ, McGovern VL, Burghes AHM. What Genetics Has Told Us and How It Can Inform Future Experiments for Spinal Muscular Atrophy, a Perspective. Int J Mol Sci 2021; 22:8494. [PMID: 34445199 PMCID: PMC8395208 DOI: 10.3390/ijms22168494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/28/2021] [Accepted: 08/04/2021] [Indexed: 02/06/2023] Open
Abstract
Proximal spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder characterized by motor neuron loss and subsequent atrophy of skeletal muscle. SMA is caused by deficiency of the essential survival motor neuron (SMN) protein, canonically responsible for the assembly of the spliceosomal small nuclear ribonucleoproteins (snRNPs). Therapeutics aimed at increasing SMN protein levels are efficacious in treating SMA. However, it remains unknown how deficiency of SMN results in motor neuron loss, resulting in many reported cellular functions of SMN and pathways affected in SMA. Herein is a perspective detailing what genetics and biochemistry have told us about SMA and SMN, from identifying the SMA determinant region of the genome, to the development of therapeutics. Furthermore, we will discuss how genetics and biochemistry have been used to understand SMN function and how we can determine which of these are critical to SMA moving forward.
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Affiliation(s)
| | | | - Arthur H. M. Burghes
- Department of Biological Chemistry & Pharmacology, The Ohio State University Wexner Medical Center, Rightmire Hall, Room 168, 1060 Carmack Road, Columbus, OH 43210, USA; (A.J.B.III); (V.L.M.)
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26
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Vargová R, Wideman JG, Derelle R, Klimeš V, Kahn RA, Dacks JB, Eliáš M. A Eukaryote-Wide Perspective on the Diversity and Evolution of the ARF GTPase Protein Family. Genome Biol Evol 2021; 13:6319025. [PMID: 34247240 PMCID: PMC8358228 DOI: 10.1093/gbe/evab157] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2021] [Indexed: 12/21/2022] Open
Abstract
The evolution of eukaryotic cellular complexity is interwoven with the extensive diversification of many protein families. One key family is the ARF GTPases that act in eukaryote-specific processes, including membrane traffic, tubulin assembly, actin dynamics, and cilia-related functions. Unfortunately, our understanding of the evolution of this family is limited. Sampling an extensive set of available genome and transcriptome sequences, we have assembled a data set of over 2,000 manually curated ARF family genes from 114 eukaryotic species, including many deeply diverged protist lineages, and carried out comprehensive molecular phylogenetic analyses. These reconstructed as many as 16 ARF family members present in the last eukaryotic common ancestor, nearly doubling the previously inferred ancient system complexity. Evidence for the wide occurrence and ancestral origin of Arf6, Arl13, and Arl16 is presented for the first time. Moreover, Arl17, Arl18, and SarB, newly described here, are absent from well-studied model organisms and as a result their function(s) remain unknown. Analyses of our data set revealed a previously unsuspected diversity of membrane association modes and domain architectures within the ARF family. We detail the step-wise expansion of the ARF family in the metazoan lineage, including discovery of several new animal-specific family members. Delving back to its earliest evolution in eukaryotes, the resolved relationship observed between the ARF family paralogs sets boundaries for scenarios of vesicle coat origins during eukaryogenesis. Altogether, our work fundamentally broadens the understanding of the diversity and evolution of a protein family underpinning the structural and functional complexity of the eukaryote cells.
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Affiliation(s)
- Romana Vargová
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Czech Republic
| | - Jeremy G Wideman
- Biodesign Center for Mechanisms of Evolution, School of Life Sciences, Arizona State University, Tempe, Arizona, USA
| | - Romain Derelle
- Station d'Ecologie Théorique et Expérimentale, UMR CNRS 5321, Moulis, France
| | - Vladimír Klimeš
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Czech Republic
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Joel B Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.,Centre for Life's Origin and Evolution, Department of Genetics, Evolution and Environment, University College of London, United Kingdom
| | - Marek Eliáš
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Czech Republic
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27
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Howard CJ, Frost A. Ribosome-associated quality control and CAT tailing. Crit Rev Biochem Mol Biol 2021; 56:603-620. [PMID: 34233554 DOI: 10.1080/10409238.2021.1938507] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Translation is the set of mechanisms by which ribosomes decode genetic messages as they synthesize polypeptides of a defined amino acid sequence. While the ribosome has been honed by evolution for high-fidelity translation, errors are inevitable. Aberrant mRNAs, mRNA structure, defective ribosomes, interactions between nascent proteins and the ribosomal exit tunnel, and insufficient cellular resources, including low tRNA levels, can lead to functionally irreversible stalls. Life thus depends on quality control mechanisms that detect, disassemble and recycle stalled translation intermediates. Ribosome-associated Quality Control (RQC) recognizes aberrant ribosome states and targets their potentially toxic polypeptides for degradation. Here we review recent advances in our understanding of RQC in bacteria, fungi, and metazoans. We focus in particular on an unusual modification made to the nascent chain known as a "CAT tail", or Carboxy-terminal Alanine and Threonine tail, and the mechanisms by which ancient RQC proteins catalyze CAT-tail synthesis.
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Affiliation(s)
- Conor J Howard
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
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28
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Jung SJ, Kim JEH, Junne T, Spiess M, Kim H. Cotranslational Targeting and Posttranslational Translocation can Cooperate in Spc3 Topogenesis. J Mol Biol 2021; 433:167109. [PMID: 34153287 DOI: 10.1016/j.jmb.2021.167109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 06/11/2021] [Accepted: 06/11/2021] [Indexed: 11/19/2022]
Abstract
Secretory and membrane proteins follow either the signal recognition particle (SRP)-dependent cotranslational translocation pathway or the SRP-independent Sec62/Sec63-dependent posttranslational pathway for their translocation across the endoplasmic reticulum (ER). However, increasing evidence suggests that most proteins are cotranslationally targeted to the ER, suggesting mixed mechanisms. It remains unclear how these two pathways cooperate. Previous studies have shown that Spc3, a signal-anchored protein, requires SRP and Sec62 for its biogenesis. This study investigated the targeting and topogenesis of Spc3 and the step at which SRP and Sec62 act using in vivo and in vitro translocation assays and co-immunoprecipitation. Our data suggest that Spc3 reaches its final topology in two steps: it enters the ER lumen head-first and then inverts its orientation. The first step is partially dependent on SRP, although independent of the Sec62/Sec63 complex. The second step is mediated by the Sec62/Sec63 complex. These data suggest that SRP and Sec62 act on a distinct step in the topogenesis of Spc3.
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Affiliation(s)
- Sung-Jun Jung
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Ji Eun Hani Kim
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Tina Junne
- Biozentrum, University of Basel, Basel, Switzerland
| | | | - Hyun Kim
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea.
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29
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Almeida C. A potential third-order role of the host endoplasmic reticulum as a contact site in interkingdom microbial endosymbiosis and viral infection. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:255-271. [PMID: 33559322 DOI: 10.1111/1758-2229.12938] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The normal functioning of eukaryotic cells depends on the compartmentalization of metabolic processes within specific organelles. Interactions among organelles, such as those between the endoplasmic reticulum (ER) - considered the largest single structure in eukaryotic cells - and other organelles at membrane contact sites (MCSs) have also been suggested to trigger synergisms, including intracellular immune responses against pathogens. In addition to the ER-endogenous functions and ER-organelle MCSs, we present the perspective of a third-order role of the ER as a host contact site for endosymbiotic microbial non-pathogens and pathogens, from endosymbiont bacteria to parasitic protists and viruses. Although understudied, ER-endosymbiont interactions have been observed in a range of eukaryotic hosts, including protists, plants, algae, and metazoans. Host ER interactions with endosymbionts could be an ER function built from ancient, conserved mechanisms selected for communicating with mutualistic endosymbionts in specific life cycle stages, and they may be exploited by pathogens and parasites. The host ER-'guest' interactome and traits in endosymbiotic biology are briefly discussed. The acknowledgment and understanding of these possible mechanisms might reveal novel evolutionary perspectives, uncover the causes of unexplained cellular disorders and suggest new pharmacological targets.
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Affiliation(s)
- Celso Almeida
- ENDOBIOS Biotech®, Praceta Progresso Clube n° 6, 2725-110 Mem-Martins, Portugal
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30
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Fernandes N, Buchan JR. RNAs as Regulators of Cellular Matchmaking. Front Mol Biosci 2021; 8:634146. [PMID: 33898516 PMCID: PMC8062979 DOI: 10.3389/fmolb.2021.634146] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/22/2021] [Indexed: 12/30/2022] Open
Abstract
RNA molecules are increasingly being identified as facilitating or impeding the interaction of proteins and nucleic acids, serving as so-called scaffolds or decoys. Long non-coding RNAs have been commonly implicated in such roles, particularly in the regulation of nuclear processes including chromosome topology, regulation of chromatin state and gene transcription, and assembly of nuclear biomolecular condensates such as paraspeckles. Recently, an increased awareness of cytoplasmic RNA scaffolds and decoys has begun to emerge, including the identification of non-coding regions of mRNAs that can also function in a scaffold-like manner to regulate interactions of nascently translated proteins. Collectively, cytoplasmic RNA scaffolds and decoys are now implicated in processes such as mRNA translation, decay, protein localization, protein degradation and assembly of cytoplasmic biomolecular condensates such as P-bodies. Here, we review examples of RNA scaffolds and decoys in both the nucleus and cytoplasm, illustrating common themes, the suitability of RNA to such roles, and future challenges in identifying and better understanding RNA scaffolding and decoy functions.
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Affiliation(s)
| | - J. Ross Buchan
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States
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31
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Wojcik S, Kriechbaumer V. Go your own way: membrane-targeting sequences. PLANT PHYSIOLOGY 2021; 185:608-618. [PMID: 33822216 PMCID: PMC8133554 DOI: 10.1093/plphys/kiaa058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/19/2020] [Indexed: 05/05/2023]
Abstract
Membrane-targeting sequences, connected targeting mechanisms, and co-factors orchestrate primary targeting of proteins to membranes.
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Affiliation(s)
- Stefan Wojcik
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Verena Kriechbaumer
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
- Author for communication: (V.K.)
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32
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Hou L, Xie J, Wu Y, Wang J, Duan A, Ao Y, Liu X, Yu X, Yan H, Perreault J, Li S. Identification of 11 candidate structured noncoding RNA motifs in humans by comparative genomics. BMC Genomics 2021; 22:164. [PMID: 33750298 PMCID: PMC7941889 DOI: 10.1186/s12864-021-07474-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 02/24/2021] [Indexed: 11/12/2022] Open
Abstract
Background Only 1.5% of the human genome encodes proteins, while large part of the remaining encodes noncoding RNAs (ncRNA). Many ncRNAs form structures and perform many important functions. Accurately identifying structured ncRNAs in the human genome and discovering their biological functions remain a major challenge. Results Here, we have established a pipeline (CM-line) with the following features for analyzing the large genomes of humans and other animals. First, we selected species with larger genetic distances to facilitate the discovery of covariations and compatible mutations. Second, we used CMfinder, which can generate useful alignments even with low sequence conservation. Third, we removed repetitive sequences and known structured ncRNAs to reduce the workload of CMfinder. Fourth, we used Infernal to find more representatives and refine the structure. We reported 11 classes of structured ncRNA candidates with significant covariations in humans. Functional analysis showed that these ncRNAs may have variable functions. Some may regulate circadian clock genes through poly (A) signals (PAS); some may regulate the elongation factor (EEF1A) and the T-cell receptor signaling pathway by cooperating with RNA binding proteins. Conclusions By searching for important features of RNA structure from large genomes, the CM-line has revealed the existence of a variety of novel structured ncRNAs. Functional analysis suggests that some newly discovered ncRNA motifs may have biological functions. The pipeline we have established for the discovery of structured ncRNAs and the identification of their functions can also be applied to analyze other large genomes. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-021-07474-9.
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Affiliation(s)
- Lijuan Hou
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Jin Xie
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Yaoyao Wu
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Jiaojiao Wang
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Anqi Duan
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Yaqi Ao
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Xuejiao Liu
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Xinmei Yu
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Hui Yan
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China
| | - Jonathan Perreault
- INRS - Institut Armand-Frappier, 531 boul des Prairies, Laval, Québec, H7V1B7, Canada
| | - Sanshu Li
- Medical School, Molecular Medicine Engineering and Research Center of Ministry of Education, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Institute of Genomics, School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, P. R. China.
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33
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Alva TR, Riera M, Chartron JW. Translational landscape and protein biogenesis demands of the early secretory pathway in Komagataella phaffii. Microb Cell Fact 2021; 20:19. [PMID: 33472617 PMCID: PMC7816318 DOI: 10.1186/s12934-020-01489-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 11/29/2020] [Indexed: 11/24/2022] Open
Abstract
Background Eukaryotes use distinct networks of biogenesis factors to synthesize, fold, monitor, traffic, and secrete proteins. During heterologous expression, saturation of any of these networks may bottleneck titer and yield. To understand the flux through various routes into the early secretory pathway, we quantified the global and membrane-associated translatomes of Komagataella phaffii. Results By coupling Ribo-seq with long-read mRNA sequencing, we generated a new annotation of protein-encoding genes. By using Ribo-seq with subcellular fractionation, we quantified demands on co- and posttranslational translocation pathways. During exponential growth in rich media, protein components of the cell-wall represent the greatest number of nascent chains entering the ER. Transcripts encoding the transmembrane protein PMA1 sequester more ribosomes at the ER membrane than any others. Comparison to Saccharomyces cerevisiae reveals conservation in the resources allocated by gene ontology, but variation in the diversity of gene products entering the secretory pathway. Conclusion A subset of host proteins, particularly cell-wall components, impose the greatest biosynthetic demands in the early secretory pathway. These proteins are potential targets in strain engineering aimed at alleviating bottlenecks during heterologous protein production.
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Affiliation(s)
- Troy R Alva
- Department of Bioengineering, University of California, Riverside, 92521, United States of America.
| | - Melanie Riera
- Department of Bioengineering, University of California, Riverside, 92521, United States of America
| | - Justin W Chartron
- Department of Bioengineering, University of California, Riverside, 92521, United States of America.,Protabit LLC, 1010 E Union St Suite 110, Pasadena, California, 91106, United States of America
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34
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Fabbiano F, Corsi J, Gurrieri E, Trevisan C, Notarangelo M, D'Agostino VG. RNA packaging into extracellular vesicles: An orchestra of RNA-binding proteins? J Extracell Vesicles 2020; 10:e12043. [PMID: 33391635 PMCID: PMC7769857 DOI: 10.1002/jev2.12043] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 11/17/2020] [Accepted: 12/03/2020] [Indexed: 12/11/2022] Open
Abstract
Extracellular vesicles (EVs) are heterogeneous membranous particles released from the cells through different biogenetic and secretory mechanisms. We now conceive EVs as shuttles mediating cellular communication, carrying a variety of molecules resulting from intracellular homeostatic mechanisms. The RNA is a widely detected cargo and, impressively, a recognized functional intermediate that elects EVs as modulators of cancer cell phenotypes, determinants of disease spreading, cell surrogates in regenerative medicine, and a source for non-invasive molecular diagnostics. The mechanistic elucidation of the intracellular events responsible for the engagement of RNA into EVs will significantly improve the comprehension and possibly the prediction of EV "quality" in association with cell physiology. Interestingly, the application of multidisciplinary approaches, including biochemical as well as cell-based and computational strategies, is increasingly revealing an active RNA-packaging process implicating RNA-binding proteins (RBPs) in the sorting of coding and non-coding RNAs. In this review, we provide a comprehensive view of RBPs recently emerging as part of the EV biology, considering the scenarios where: (i) individual RBPs were detected in EVs along with their RNA substrates, (ii) RBPs were detected in EVs with inferred RNA targets, and (iii) EV-transcripts were found to harbour sequence motifs mirroring the activity of RBPs. Proteins so far identified are members of the hnRNP family (hnRNPA2B1, hnRNPC1, hnRNPG, hnRNPH1, hnRNPK, and hnRNPQ), as well as YBX1, HuR, AGO2, IGF2BP1, MEX3C, ANXA2, ALIX, NCL, FUS, TDP-43, MVP, LIN28, SRP9/14, QKI, and TERT. We describe the RBPs based on protein domain features, current knowledge on the association with human diseases, recognition of RNA consensus motifs, and the need to clarify the functional significance in different cellular contexts. We also summarize data on previously identified RBP inhibitor small molecules that could also be introduced in EV research as potential modulators of vesicular RNA sorting.
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Affiliation(s)
- Fabrizio Fabbiano
- Department of CellularComputational and Integrative Biology (CIBIO)University of TrentoTrentoItaly
| | - Jessica Corsi
- Department of CellularComputational and Integrative Biology (CIBIO)University of TrentoTrentoItaly
| | - Elena Gurrieri
- Department of CellularComputational and Integrative Biology (CIBIO)University of TrentoTrentoItaly
| | - Caterina Trevisan
- Department of CellularComputational and Integrative Biology (CIBIO)University of TrentoTrentoItaly
| | - Michela Notarangelo
- Department of CellularComputational and Integrative Biology (CIBIO)University of TrentoTrentoItaly
| | - Vito G. D'Agostino
- Department of CellularComputational and Integrative Biology (CIBIO)University of TrentoTrentoItaly
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35
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Lu L, Xu X, Du X, Zeng T, Yang T, Chen Y, Tao Z, Zhong S, Wen J, Zhou C. Transcriptome analyses to reveal the dynamic change mechanism of pigeon magnum during one egg-laying cycle. Mol Reprod Dev 2020; 87:1141-1151. [PMID: 33084116 DOI: 10.1002/mrd.23428] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/29/2020] [Accepted: 09/12/2020] [Indexed: 12/14/2022]
Abstract
We analyzed the transcriptome of pigeon magnum in three stages (C1: pre-ovulation, C2: post-ovulation, C3: 5-6 days after ovulation) to elucidate the molecular and cellular events associated with morphological changes during the laying cycle. We observed that C1 was highly developed, apoptosis rate was highest in C2, and C3 attained the smallest size. Through RNA-sequencing, we obtained 54,764,938 (97.2%) high-quality clean reads that aligned to 20,767 genes. Gene expression profile analysis showed the greatest difference between C1 and C3; 3966 differentially expressed genes (DEGs) were identified, of which 2250 genes were upregulated and 1716 genes were downregulated in C1. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that protein processing and transport activities were prominent in C1, and upregulated genes included those related to signal recognition particle (SRP), signal recognition particle receptor (SRPR), translocon, GRP78, RRBP1, TRAP, TRAM1, and OST. Egg white protein-related gene expression was highest, with OVALY being the most highly expressed. In C2, apoptosis-related gene expression was higher than in C1, and fatty acid metabolism was active, which may be correlated with magnum tissue regression. Collagen- and laminin-related gene expression was prominent in C1 and C3, indicating roles in egg white protein generation and magnum reconstruction. PR gene expression was highest and exhibited drastic change in the three groups, indicating that PR and its regulation may be involved in changes in magnum morphology and function. Through the identification and functional analysis of DEGs and other crucial genes, this may contribute to understand the egg white protein production, magnum tissue regression, and magnum regeneration mechanisms.
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Affiliation(s)
- Lizhi Lu
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Science, Hangzhou, Zhejiang, China
| | - Xiaoqin Xu
- Institute of Ecology, China West Normal University, Nanchong, Sichuan, China
| | - Xue Du
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Science, Hangzhou, Zhejiang, China
| | - Tao Zeng
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Science, Hangzhou, Zhejiang, China
| | - Tingbang Yang
- Institute of Ecology, China West Normal University, Nanchong, Sichuan, China
| | - Yao Chen
- Institute of Ecology, China West Normal University, Nanchong, Sichuan, China
| | - Zhengrong Tao
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Science, Hangzhou, Zhejiang, China
| | - Shengliang Zhong
- PingYang XingLiang Pigeon Farming Co. Ltd., Wenzhou, Zhejiang, China
| | - Jihui Wen
- PingYang AoFeng Pigeon Farming Co. Ltd., Wenzhou, Zhejiang, China
| | - Caiquan Zhou
- Institute of Ecology, China West Normal University, Nanchong, Sichuan, China
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36
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Chitwood PJ, Hegde RS. An intramembrane chaperone complex facilitates membrane protein biogenesis. Nature 2020; 584:630-634. [PMID: 32814900 DOI: 10.1038/s41586-020-2624-y] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 05/21/2020] [Indexed: 12/31/2022]
Abstract
Integral membrane proteins are encoded by approximately 25% of all protein-coding genes1. In eukaryotes, the majority of membrane proteins are inserted, modified and folded at the endoplasmic reticulum (ER)2. Research over the past several decades has determined how membrane proteins are targeted to the ER and how individual transmembrane domains (TMDs) are inserted into the lipid bilayer3. By contrast, very little is known about how multi-spanning membrane proteins with several TMDs are assembled within the membrane. During the assembly of TMDs, interactions between polar or charged amino acids typically stabilize the final folded configuration4-8. TMDs with hydrophilic amino acids are likely to be chaperoned during the co-translational biogenesis of membrane proteins; however, ER-resident intramembrane chaperones are poorly defined. Here we identify the PAT complex, an abundant obligate heterodimer of the widely conserved ER-resident membrane proteins CCDC47 and Asterix. The PAT complex engages nascent TMDs that contain unshielded hydrophilic side chains within the lipid bilayer, and it disengages concomitant with substrate folding. Cells that lack either subunit of the PAT complex show reduced biogenesis of numerous multi-spanning membrane proteins. Thus, the PAT complex is an intramembrane chaperone that protects TMDs during assembly to minimize misfolding of multi-spanning membrane proteins and maintain cellular protein homeostasis.
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Kloska A, Cech GM, Sadowska M, Krause K, Szalewska-Pałasz A, Olszewski P. Adaptation of the Marine Bacterium Shewanella baltica to Low Temperature Stress. Int J Mol Sci 2020; 21:ijms21124338. [PMID: 32570789 PMCID: PMC7352654 DOI: 10.3390/ijms21124338] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 06/11/2020] [Accepted: 06/15/2020] [Indexed: 11/30/2022] Open
Abstract
Marine bacteria display significant versatility in adaptation to variations in the environment and stress conditions, including temperature shifts. Shewanella baltica plays a major role in denitrification and bioremediation in the marine environment, but is also identified to be responsible for spoilage of ice-stored seafood. We aimed to characterize transcriptional response of S. baltica to cold stress in order to achieve a better insight into mechanisms governing its adaptation. We exposed bacterial cells to 8 °C for 90 and 180 min, and assessed changes in the bacterial transcriptome with RNA sequencing validated with the RT-qPCR method. We found that S. baltica general response to cold stress is associated with massive downregulation of gene expression, which covered about 70% of differentially expressed genes. Enrichment analysis revealed upregulation of only few pathways, including aminoacyl-tRNA biosynthesis, sulfur metabolism and the flagellar assembly process. Downregulation was observed for fatty acid degradation, amino acid metabolism and a bacterial secretion system. We found that the entire type II secretion system was transcriptionally shut down at low temperatures. We also observed transcriptional reprogramming through the induction of RpoE and repression of RpoD sigma factors to mediate the cold stress response. Our study revealed how diverse and complex the cold stress response in S. baltica is.
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Affiliation(s)
- Anna Kloska
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
- Correspondence: (A.K.); (P.O.)
| | - Grzegorz M. Cech
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland; (G.M.C.); (M.S.); (K.K.); (A.S.-P.)
| | - Marta Sadowska
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland; (G.M.C.); (M.S.); (K.K.); (A.S.-P.)
| | - Klaudyna Krause
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland; (G.M.C.); (M.S.); (K.K.); (A.S.-P.)
| | - Agnieszka Szalewska-Pałasz
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland; (G.M.C.); (M.S.); (K.K.); (A.S.-P.)
| | - Paweł Olszewski
- 3P Medicine Laboratory, International Research Agenda, Medical University of Gdańsk, Dębinki 7, 80-211 Gdańsk, Poland
- Correspondence: (A.K.); (P.O.)
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The Perlman syndrome DIS3L2 exoribonuclease safeguards endoplasmic reticulum-targeted mRNA translation and calcium ion homeostasis. Nat Commun 2020; 11:2619. [PMID: 32457326 PMCID: PMC7250864 DOI: 10.1038/s41467-020-16418-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 04/30/2020] [Indexed: 11/16/2022] Open
Abstract
DIS3L2-mediated decay (DMD) is a surveillance pathway for certain non-coding RNAs (ncRNAs) including ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), small nuclear RNAs (snRNAs), and RMRP. While mutations in DIS3L2 are associated with Perlman syndrome, the biological significance of impaired DMD is obscure and pathological RNAs have not been identified. Here, by ribosome profiling (Ribo-seq) we find specific dysregulation of endoplasmic reticulum (ER)-targeted mRNA translation in DIS3L2-deficient cells. Mechanistically, DMD functions in the quality control of the 7SL ncRNA component of the signal recognition particle (SRP) required for ER-targeted translation. Upon DIS3L2 loss, sustained 3’-end uridylation of aberrant 7SL RNA impacts ER-targeted translation and causes ER calcium leakage. Consequently, elevated intracellular calcium in DIS3L2-deficient cells activates calcium signaling response genes and perturbs ESC differentiation. Thus, DMD is required to safeguard ER-targeted mRNA translation, intracellular calcium homeostasis, and stem cell differentiation. The DIS3L2 exonuclease degrades aberrant 7SL RNAs tagged by an oligouridine 3′-tail. Here the authors analyze DIS3L2 knockout mouse embryonic stem cells and suggest that DIS3L2-mediated quality control of 7SL RNA is important for ER-mediated translation and calcium ion homeostasis.
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Juarez-Navarro K, Ayala-Garcia VM, Ruiz-Baca E, Meneses-Morales I, Rios-Banuelos JL, Lopez-Rodriguez A. Assistance for Folding of Disease-Causing Plasma Membrane Proteins. Biomolecules 2020; 10:biom10050728. [PMID: 32392767 PMCID: PMC7277483 DOI: 10.3390/biom10050728] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 04/16/2020] [Accepted: 04/21/2020] [Indexed: 02/06/2023] Open
Abstract
An extensive catalog of plasma membrane (PM) protein mutations related to phenotypic diseases is associated with incorrect protein folding and/or localization. These impairments, in addition to dysfunction, frequently promote protein aggregation, which can be detrimental to cells. Here, we review PM protein processing, from protein synthesis in the endoplasmic reticulum to delivery to the PM, stressing the main repercussions of processing failures and their physiological consequences in pathologies, and we summarize the recent proposed therapeutic strategies to rescue misassembled proteins through different types of chaperones and/or small molecule drugs that safeguard protein quality control and regulate proteostasis.
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40
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Brooks W. An Epigenetics-Based Hypothesis of Autoantigen Development in Systemic Lupus Erythematosus. EPIGENOMES 2020; 4:epigenomes4020006. [PMID: 34968240 PMCID: PMC8594704 DOI: 10.3390/epigenomes4020006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 04/20/2020] [Indexed: 11/16/2022] Open
Abstract
Currently, we have a limited understanding of mechanisms leading to systemic lupus erythematosus, but we know that genetics, environmental factors, and epigenetics contribute to the disease. One common aspect of the various environmental triggers is that they can cause cellular stress. When extraordinary stress occurs, such as viral activation, a cell's response can include increased nucleolar volume and activity to produce more machinery (e.g., ribosomes) to help the cell recover. However, nucleolar expansion can disrupt the epigenetic control in neighboring heterochromatin that comprises the nucleolar shell. This disruption can open underlying vulnerabilities that provoke an autoimmune reaction. Here, we review the "X chromosome-nucleolus nexus" hypothesis, which explains how nucleolar stress can disrupt epigenetically silenced chromatin, especially the neighboring inactive X chromosome (aka the nucleolar satellite). Chromatin disruption can lead to the expression of sequestered DNA, such as Alu elements and fully functional LINE-1 reverse transcriptase genes. In addition, Alu transcripts can disrupt the nucleolar structural integrity, leading to nucleolar disintegration. Such disintegration can leave nucleolar components and products in autoantigenic forms, such as abnormal conformations or incomplete macromolecular assemblies. Recent research on DNA sensing pathways can now be incorporated into the hypothesis to provide further details explaining how autoantibodies to endogenous nucleic acids arise.
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Affiliation(s)
- Wesley Brooks
- Department of Chemistry, University of South Florida, Tampa, FL 33620, USA
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41
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Riboregulation in Nitrogen-Fixing Endosymbiotic Bacteria. Microorganisms 2020; 8:microorganisms8030384. [PMID: 32164262 PMCID: PMC7143759 DOI: 10.3390/microorganisms8030384] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/04/2020] [Accepted: 03/05/2020] [Indexed: 01/21/2023] Open
Abstract
Small non-coding RNAs (sRNAs) are ubiquitous components of bacterial adaptive regulatory networks underlying stress responses and chronic intracellular infection of eukaryotic hosts. Thus, sRNA-mediated regulation of gene expression is expected to play a major role in the establishment of mutualistic root nodule endosymbiosis between nitrogen-fixing rhizobia and legume plants. However, knowledge about this level of genetic regulation in this group of plant-interacting bacteria is still rather scarce. Here, we review insights into the rhizobial non-coding transcriptome and sRNA-mediated post-transcriptional regulation of symbiotic relevant traits such as nutrient uptake, cell cycle, quorum sensing, or nodule development. We provide details about the transcriptional control and protein-assisted activity mechanisms of the functionally characterized sRNAs involved in these processes. Finally, we discuss the forthcoming research on riboregulation in legume symbionts.
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42
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Witham CM, Dassanayake HG, Paxman AL, Stevens KLP, Baklous L, White PF, Black AL, Steuart RFL, Stirling CJ, Schulz BL, Mousley CJ. The conserved C-terminus of Sss1p is required to maintain the endoplasmic reticulum permeability barrier. J Biol Chem 2019; 295:2125-2134. [PMID: 31848225 DOI: 10.1074/jbc.ra119.010378] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 12/11/2019] [Indexed: 11/06/2022] Open
Abstract
The endoplasmic reticulum (ER) is the entry point to the secretory pathway and major site of protein biogenesis. Translocation of secretory and integral membrane proteins across or into the ER membrane occurs via the evolutionarily conserved Sec61 complex, a heterotrimeric channel that comprises the Sec61p/Sec61α, Sss1p/Sec61γ, and Sbh1p/Sec61β subunits. In addition to forming a protein-conducting channel, the Sec61 complex also functions to maintain the ER permeability barrier, preventing the mass free flow of essential ER-enriched molecules and ions. Loss in Sec61 integrity is detrimental and implicated in the progression of disease. The Sss1p/Sec61γ C terminus is juxtaposed to the key gating module of Sec61p/Sec61α, and we hypothesize it is important for gating the ER translocon. The ER stress response was found to be constitutively induced in two temperature-sensitive sss1 mutants (sss1ts ) that are still proficient to conduct ER translocation. A screen to identify intergenic mutations that allow for sss1ts cells to grow at 37 °C suggests the ER permeability barrier to be compromised in these mutants. We propose the extreme C terminus of Sss1p/Sec61γ is an essential component of the gating module of the ER translocase and is required to maintain the ER permeability barrier.
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Affiliation(s)
- Christopher M Witham
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia; Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia
| | - Hasindu G Dassanayake
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia
| | - Aleshanee L Paxman
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia
| | - Kofi L P Stevens
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia; Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia
| | - Lamprini Baklous
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia; Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia
| | - Paris F White
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia
| | - Amy L Black
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia; Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia
| | - Robert F L Steuart
- Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia
| | - Colin J Stirling
- School of Biological Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Benjamin L Schulz
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane St Lucia, QLD 4072, Australia
| | - Carl J Mousley
- School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia; Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia.
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43
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Van Puyenbroeck V, Pauwels E, Provinciael B, Bell TW, Schols D, Kalies KU, Hartmann E, Vermeire K. Preprotein signature for full susceptibility to the co-translational translocation inhibitor cyclotriazadisulfonamide. Traffic 2019; 21:250-264. [PMID: 31675144 DOI: 10.1111/tra.12713] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/24/2019] [Accepted: 10/26/2019] [Indexed: 01/13/2023]
Abstract
Cyclotriazadisulfonamide (CADA) inhibits the co-translational translocation of human CD4 (huCD4) into the endoplasmic reticulum lumen in a signal peptide (SP)-dependent way. We propose that CADA binds the nascent huCD4 SP in a folded conformation within the translocon resembling a normally transitory state during translocation. Here, we used alanine scanning on the huCD4 SP to identify the signature for full susceptibility to CADA. In accordance with our previous work, we demonstrate that residues in the vicinity of the hydrophobic h-region are critical for sensitivity to CADA. In particular, exchanging Gln-15, Val-17 or Pro-20 in the huCD4 SP for Ala resulted in a resistant phenotype. Together with positively charged residues at the N-terminal portion of the mature protein, these residues mediate full susceptibility to the co-translational translocation inhibitory activity of CADA towards huCD4. In addition, sensitivity to CADA is inversely related to hydrophobicity in the huCD4 SP. In vitro translocation experiments confirmed that the general hydrophobicity of the h-domain and positive charges in the mature protein are key elements that affect both the translocation efficiency of huCD4 and the sensitivity towards CADA. Besides these two general SP parameters that determine the functionality of the signal sequence, unique amino acid pairs (L14/Q15 and L19/P20) in the SP hydrophobic core add specificity to the sensitivity signature for a co-translational translocation inhibitor.
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Affiliation(s)
- Victor Van Puyenbroeck
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Eva Pauwels
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Becky Provinciael
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Thomas W Bell
- Department of Chemistry, University of Nevada, Reno, Nevada
| | - Dominique Schols
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Kai-Uwe Kalies
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck, Germany
| | - Enno Hartmann
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck, Germany
| | - Kurt Vermeire
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
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44
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Fukuda S, Yan S, Komi Y, Sun M, Gabizon R, Bustamante C. The Biogenesis of SRP RNA Is Modulated by an RNA Folding Intermediate Attained during Transcription. Mol Cell 2019; 77:241-250.e8. [PMID: 31706702 DOI: 10.1016/j.molcel.2019.10.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 08/29/2019] [Accepted: 10/04/2019] [Indexed: 11/16/2022]
Abstract
The signal recognition particle (SRP), responsible for co-translational protein targeting and delivery to cellular membranes, depends on the native long-hairpin fold of its RNA to confer functionality. Since RNA initiates folding during its synthesis, we used high-resolution optical tweezers to follow in real time the co-transcriptional folding of SRP RNA. Surprisingly, SRP RNA folding is robust to transcription rate changes and the presence or absence of its 5'-precursor sequence. The folding pathway also reveals the obligatory attainment of a non-native hairpin intermediate (H1) that eventually rearranges into the native fold. Furthermore, H1 provides a structural platform alternative to the native fold for RNase P to bind and mature SRP RNA co-transcriptionally. Delays in attaining the final native fold are detrimental to the cell, altogether showing that a co-transcriptional folding pathway underpins the proper biogenesis of function-essential SRP RNA.
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Affiliation(s)
- Shingo Fukuda
- Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, CA, USA; Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Science, Tokyo, Japan; Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa 920-1192, Japan.
| | - Shannon Yan
- Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
| | - Yusuke Komi
- Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, CA, USA; Laboratory for Protein Conformation Diseases, RIKEN Center for Brain Science, Wako, Saitama, Japan
| | - Mingxuan Sun
- Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Ronen Gabizon
- Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, CA, USA
| | - Carlos Bustamante
- Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, Berkeley, CA, USA; Biophysics Graduate Group, University of California, Berkeley, Berkeley, CA, USA; Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA; Department of Physics, University of California, Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA; Kavli Energy Nanoscience Institute, University of California, Berkeley, Berkeley, CA, USA.
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45
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Deuerling E, Gamerdinger M, Kreft SG. Chaperone Interactions at the Ribosome. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033977. [PMID: 30833456 DOI: 10.1101/cshperspect.a033977] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The continuous refreshment of the proteome is critical to maintain protein homeostasis and to adapt cells to changing conditions. Thus, de novo protein biogenesis by ribosomes is vitally important to every cellular system. This process is delicate and error-prone and requires, besides cytosolic chaperones, the guidance by a specialized set of molecular chaperones that bind transiently to the translation machinery and the nascent protein to support early folding events and to regulate cotranslational protein transport. These chaperones include the bacterial trigger factor (TF), the archaeal and eukaryotic nascent polypeptide-associated complex (NAC), and the eukaryotic ribosome-associated complex (RAC). This review focuses on the structures, functions, and substrates of these ribosome-associated chaperones and highlights the most recent findings about their potential mechanisms of action.
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Affiliation(s)
- Elke Deuerling
- Molecular Microbiology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Martin Gamerdinger
- Molecular Microbiology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Stefan G Kreft
- Molecular Microbiology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany
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46
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Hegde RS, Zavodszky E. Recognition and Degradation of Mislocalized Proteins in Health and Disease. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033902. [PMID: 30833453 DOI: 10.1101/cshperspect.a033902] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A defining feature of eukaryotic cells is the segregation of complex biochemical processes among different intracellular compartments. The protein targeting, translocation, and trafficking pathways that sustain compartmentalization must recognize a diverse range of clients via degenerate signals. This recognition is imperfect, resulting in polypeptides at incorrect cellular locations. Cells have evolved mechanisms to selectively recognize mislocalized proteins and triage them for degradation or rescue. These spatial quality control pathways maintain cellular protein homeostasis, become especially important during organelle stress, and might contribute to disease when they are impaired or overwhelmed.
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Affiliation(s)
- Ramanujan S Hegde
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Eszter Zavodszky
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
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47
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Abstract
One-fourth of eukaryotic genes code for integral membrane proteins, nearly all of which are inserted and assembled at the endoplasmic reticulum (ER). The defining feature of membrane proteins is one or more transmembrane domains (TMDs). During membrane protein biogenesis, TMDs are selectively recognized, shielded, and chaperoned into the lipid bilayer, where they often assemble with other TMDs. If maturation fails, exposed TMDs serve as a cue for engagement of degradation pathways. Thus, TMD-recognition factors in the cytosol and ER are essential for membrane protein biogenesis and quality control. Here, we discuss the growing assortment of cytosolic and membrane-embedded TMD-recognition factors, the pathways within which they operate, and mechanistic principles of recognition.
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48
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Proper insertion and topogenesis of membrane proteins in the ER depend on Sec63. Biochim Biophys Acta Gen Subj 2019; 1863:1371-1380. [DOI: 10.1016/j.bbagen.2019.06.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 05/28/2019] [Accepted: 06/04/2019] [Indexed: 11/30/2022]
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49
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Bezzerri V, Cipolli M. Shwachman-Diamond Syndrome: Molecular Mechanisms and Current Perspectives. Mol Diagn Ther 2019; 23:281-290. [PMID: 30413969 DOI: 10.1007/s40291-018-0368-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Shwachman-Diamond syndrome (SDS) is a rare inherited disease mainly caused by mutations in the Shwachman-Bodian-Diamond Syndrome (SBDS) gene. However, it has recently been reported that other genes, including DnaJ heat shock protein family (Hsp40) member C21 (DNAJC21), elongation factor-like 1 (EFL1) and signal recognition particle 54 (SRP54) are also associated with an SDS-like phenotype. Interestingly, SBDS, DNAJC21, EFL1 and SRP54 are involved in ribosome biogenesis: SBDS, through direct interaction with EFL1, promotes the release of the eukaryotic initiation factor 6 (eIF6) during ribosome maturation, DNAJC21 stabilizes the 80S ribosome, and SRP54 facilitates protein trafficking. These findings strengthen the postulate that SDS is a ribosomopathy. SDS is a multiple-organ disease mainly characterized by bone marrow failure, bone malformations, pancreatic insufficiency and cognitive disorders. Almost 15-20% of patients with SDS present myelodysplastic syndrome with a high risk of acute myeloid leukemia (AML) transformation. Unfortunately, besides bone marrow transplantation, no gene-based therapy for SDS has yet been developed. This review aims to recapitulate the recent findings on the molecular mechanisms of SDS underlying bone marrow failure, hematopoiesis and AML development and to draw a realistic picture of current perspectives.
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Affiliation(s)
- Valentino Bezzerri
- Cystic Fibrosis Center, Azienda Ospedaliero Universitaria Ospedali Riuniti di Ancona, Via Conca 71, 60126, Torrette, Ancona, Italy
| | - Marco Cipolli
- Cystic Fibrosis Center, Azienda Ospedaliero Universitaria Ospedali Riuniti di Ancona, Via Conca 71, 60126, Torrette, Ancona, Italy.
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50
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Early Scanning of Nascent Polypeptides inside the Ribosomal Tunnel by NAC. Mol Cell 2019; 75:996-1006.e8. [PMID: 31377116 DOI: 10.1016/j.molcel.2019.06.030] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/08/2019] [Accepted: 06/19/2019] [Indexed: 11/24/2022]
Abstract
Cotranslational processing of newly synthesized proteins is fundamental for correct protein maturation. Protein biogenesis factors are thought to bind nascent polypeptides not before they exit the ribosomal tunnel. Here, we identify a nascent chain recognition mechanism deep inside the ribosomal tunnel by an essential eukaryotic cytosolic chaperone. The nascent polypeptide-associated complex (NAC) inserts the N-terminal tail of its β subunit (N-βNAC) into the ribosomal tunnel to sense substrates directly upon synthesis close to the peptidyl-transferase center. N-βNAC escorts the growing polypeptide to the cytosol and relocates to an alternate binding site on the ribosomal surface. Using C. elegans as an in vivo model, we demonstrate that the tunnel-probing activity of NAC is essential for organismal viability and critical to regulate endoplasmic reticulum (ER) protein transport by controlling ribosome-Sec61 translocon interactions. Thus, eukaryotic protein maturation relies on the early sampling of nascent chains inside the ribosomal tunnel.
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