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Li L, Han J, Lo HYG, Tam WWL, Jia H, Tse ECM, Taliaferro JM, Li Y. Symmetry-breaking malachite green as a near-infrared light-activated fluorogenic photosensitizer for RNA proximity labeling. Nucleic Acids Res 2024; 52:e36. [PMID: 38407347 DOI: 10.1093/nar/gkae125] [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: 11/02/2023] [Revised: 01/17/2024] [Accepted: 02/08/2024] [Indexed: 02/27/2024] Open
Abstract
Cellular RNA is asymmetrically distributed in cells and the regulation of RNA localization is crucial for proper cellular functions. However, limited chemical tools are available to capture dynamic RNA localization in complex biological systems with high spatiotemporal resolution. Here, we developed a new method for RNA proximity labeling activated by near-infrared (NIR) light, which holds the potential for deep penetration. Our method, termed FAP-seq, utilizes a genetically encoded fluorogen activating protein (FAP) that selectively binds to a set of substrates known as malachite green (MG). FAP binding restricts the rotation of MG and rapidly activates its fluorescence in a wash-free manner. By introducing a monoiodo modification to MG, we created a photosensitizer (MG-HI) with the highest singlet oxygen generation ability among various MG derivatives, enabling both protein and RNA proximity labeling in live cells. New insights are provided in the transcriptome analysis with FAP-seq, while a deeper understanding of the symmetry-breaking structural arrangement of FAP-MG-HI was obtained through molecular dynamics simulations. Overall, our wash-free and NIR light-inducible RNA proximity labeling method (FAP-seq) offers a powerful and versatile approach for investigating complex mechanisms underlying RNA-related biological processes.
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Affiliation(s)
- Lan Li
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Jinghua Han
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Hei-Yong G Lo
- Department of Biochemistry and Molecular Genetics, RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Winnie Wai Ling Tam
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
- Laboratory for Synthetic Chemistry and Chemical Biology Limited, New Territories, Hong Kong 999077, China
| | - Han Jia
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
| | - Edmund Chun Ming Tse
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
- Laboratory for Synthetic Chemistry and Chemical Biology Limited, New Territories, Hong Kong 999077, China
- CAS-HKU Joint Laboratory of Metallomics on Health and Environment, The University of Hong Kong, Hong Kong 999077, China
| | - J Matthew Taliaferro
- Department of Biochemistry and Molecular Genetics, RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Ying Li
- Department of Chemistry, The University of Hong Kong, Hong Kong 999077, China
- Laboratory for Synthetic Chemistry and Chemical Biology Limited, New Territories, Hong Kong 999077, China
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Nicchitta CV. An emerging role for the endoplasmic reticulum in stress granule biogenesis. Semin Cell Dev Biol 2024; 156:160-166. [PMID: 36202692 PMCID: PMC10208384 DOI: 10.1016/j.semcdb.2022.09.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 09/07/2022] [Accepted: 09/26/2022] [Indexed: 11/07/2022]
Abstract
Stress granules (SGs), structurally dynamic, optically resolvable, macromolecular assemblies of mRNAs, RNA binding proteins (RBPs), translation factors, ribosomal subunits, as well as other interacting proteins, assemble in response to cell stress conditions that elicit phosphorylation of eukaryotic initiation factor 2α (eIF2α) and consequently, the inactivation of translation initiation. SG biology is conserved throughout eukaryotes and has recently been linked to the pathological sequelae of neurodegenerative disorders, cancer biology, and viral infection. Substantial insights into mechanisms of SG biogenesis, and more broadly the phenomenon of biological liquid-liquid phase separation (LLPS), have been aided by detailed proteomic and transcriptomic studies as well as in vitro reconstitution approaches. A particularly interesting and largely unexplored element of SG biology is the cell biological context of SG biogenesis, including its subcellular organization and more recently, evidence that the endoplasmic reticulum (ER) membrane may serve important functions in RNA granule biology generally and SG biogenesis specifically. A central role for the ER in SG biogenesis is discussed and a hypothesis linking SG formation on the ER to the trafficking, localization and de novo translation of newly exported mRNAs is presented.
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Stixová L, Tichý V, Bártová E. RNA-related DNA damage and repair: The role of N7-methylguanosine in the cell nucleus exposed to UV light. Heliyon 2024; 10:e25599. [PMID: 38370261 PMCID: PMC10869776 DOI: 10.1016/j.heliyon.2024.e25599] [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: 08/22/2023] [Revised: 01/30/2024] [Accepted: 01/30/2024] [Indexed: 02/20/2024] Open
Abstract
Background Chemical modifications in mRNAs, tRNAs, rRNAs, and non-coding RNAs stabilize these nucleic acids and regulate their function. In addition to regulating the translation of genetic information from mRNA to proteins, it has been revealed that modifications in RNAs regulate repair processes in the genome. Methods Using local laser microirradiation, confocal microscopy, dot blots, and mass spectrometry we studied the role of N7-methylguanosine (m7G), which is co-transcriptionally installed in RNA. Results Here, we show that after UVC and UVA irradiation, the level of m7G RNA is increased initially in the cytoplasm, and after local laser microirradiation, m7G RNA is highly abundant in UVA-damaged chromatin. This process is poly(ADP-ribose) polymerase (PARP)-dependent, but not accompanied by changes in the level of m7G-writers, including methyltransferases RNMT, METTL1, and WBSCR22. We also observed that METTL1 deficiency does not affect the recruitment of m7G RNA to microirradiated chromatin. Analyzing the levels of mRNA, let-7e, and miR-203a in both the cytoplasm and the cell nucleus, we revealed that UVC irradiation changed the level of mRNA, and significantly increased the pool of both let-7e and miR-203a, which correlated with radiation-induced m7G RNA increase in the cytoplasm. Conclusions Irradiation by UV light increases the m7G RNA pool in the cytoplasm and in the microirradiated genome. Thus, epigenetically modified RNAslikely contribute to DNA damage responses or m7G signals the presence of RNA damage.
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Affiliation(s)
- Lenka Stixová
- Department of Cell Biology and Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, Czech Republic
| | - Vlastimil Tichý
- Department of Cell Biology and Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, Czech Republic
| | - Eva Bártová
- Department of Cell Biology and Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, Czech Republic
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Archuleta SR, Goodrich JA, Kugel JF. Mechanisms and Functions of the RNA Polymerase II General Transcription Machinery during the Transcription Cycle. Biomolecules 2024; 14:176. [PMID: 38397413 PMCID: PMC10886972 DOI: 10.3390/biom14020176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 01/29/2024] [Accepted: 01/30/2024] [Indexed: 02/25/2024] Open
Abstract
Central to the development and survival of all organisms is the regulation of gene expression, which begins with the process of transcription catalyzed by RNA polymerases. During transcription of protein-coding genes, the general transcription factors (GTFs) work alongside RNA polymerase II (Pol II) to assemble the preinitiation complex at the transcription start site, open the promoter DNA, initiate synthesis of the nascent messenger RNA, transition to productive elongation, and ultimately terminate transcription. Through these different stages of transcription, Pol II is dynamically phosphorylated at the C-terminal tail of its largest subunit, serving as a control mechanism for Pol II elongation and a signaling/binding platform for co-transcriptional factors. The large number of core protein factors participating in the fundamental steps of transcription add dense layers of regulation that contribute to the complexity of temporal and spatial control of gene expression within any given cell type. The Pol II transcription system is highly conserved across different levels of eukaryotes; however, most of the information here will focus on the human Pol II system. This review walks through various stages of transcription, from preinitiation complex assembly to termination, highlighting the functions and mechanisms of the core machinery that participates in each stage.
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Affiliation(s)
| | - James A. Goodrich
- Department of Biochemistry, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA;
| | - Jennifer F. Kugel
- Department of Biochemistry, University of Colorado Boulder, 596 UCB, Boulder, CO 80309, USA;
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Niikura M, Fukutomi T, Mitobe J, Kobayashi F. Characterization of a nuclear transport factor 2-like domain-containing protein in Plasmodium berghei. Malar J 2024; 23:13. [PMID: 38195464 PMCID: PMC10777651 DOI: 10.1186/s12936-024-04839-9] [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: 05/17/2023] [Accepted: 01/03/2024] [Indexed: 01/11/2024] Open
Abstract
BACKGROUND Plasmodium lacks an mRNA export receptor ortholog, such as yeast Mex67. Yeast Mex67 contains a nuclear transport factor 2 (NTF2)-like domain, suggesting that NTF2-like domain-containing proteins might be associated with mRNA export in Plasmodium. In this study, the relationship between mRNA export and an NTF2-like domain-containing protein, PBANKA_1019700, was investigated using the ANKA strain of rodent malaria parasite Plasmodium berghei. METHODS The deletion mutant Δ1019700 was generated by introducing gene-targeting vectors into the P. berghei ANKA genome, and parasite growth and virulence were examined. To investigate whether PBANKA_1019700 is involved in mRNA export, live-cell fluorescence imaging and immunoprecipitation coupled to mass spectrometry (IP-MS) were performed using transgenic parasites expressing fusion proteins (1019700::mCherry). RESULTS Deletion of PBANKA_1019700 affected the sexual phase but not the asexual phase of malaria parasites. Live-cell fluorescence imaging showed that PBANKA_1019700 localizes to the cytoplasm. Moreover, IP-MS analysis of 1019700::mCherry indicated that PBANKA_1019700 interacts with ubiquitin-related proteins but not nuclear proteins. CONCLUSIONS PBANKA_1019700 is a noncanonical NTF2-like superfamily protein.
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Affiliation(s)
- Mamoru Niikura
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan.
| | - Toshiyuki Fukutomi
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
| | - Jiro Mitobe
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan
| | - Fumie Kobayashi
- Department of Environmental Science, School of Life and Environmental Science, Azabu University, Kanagawa, 252-5201, Japan
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Park SC, Lee YS, Cho KA, Kim SY, Lee YI, Lee SR, Lim IK. What matters in aging is signaling for responsiveness. Pharmacol Ther 2023; 252:108560. [PMID: 37952903 DOI: 10.1016/j.pharmthera.2023.108560] [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: 06/04/2023] [Revised: 10/03/2023] [Accepted: 11/06/2023] [Indexed: 11/14/2023]
Abstract
Biological responsiveness refers to the capacity of living organisms to adapt to changes in both their internal and external environments through physiological and behavioral mechanisms. One of the prominent aspects of aging is the decline in this responsiveness, which can lead to a deterioration in the processes required for maintenance, survival, and growth. The vital link between physiological responsiveness and the essential life processes lies within the signaling systems. To devise effective strategies for controlling the aging process, a comprehensive reevaluation of this connecting loop is imperative. This review aims to explore the impact of aging on signaling systems responsible for responsiveness and introduce a novel perspective on intervening in the aging process by restoring the compromised responsiveness. These innovative mechanistic approaches for modulating altered responsiveness hold the potential to illuminate the development of action plans aimed at controlling the aging process and treating age-related disorders.
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Affiliation(s)
- Sang Chul Park
- The Future Life & Society Research Center, Advanced Institute of Aging Science, Chonnam National University, Gwangju 61469, Republic of Korea.
| | - Young-Sam Lee
- Department of New Biology, DGIST, Daegu 42988, Republic of Korea; Well Aging Research Center, Division of Biotechnology, DGIST, Daegu 42988, Republic of Korea.
| | - Kyung A Cho
- Department of Biochemistry, Chonnam National University Medical School, Jeollanam-do 58128, Republic of Korea
| | - Sung Young Kim
- Department of Biochemistry, Konkuk University School of Medicine, Seoul 05029, Republic of Korea
| | - Yun-Il Lee
- Well Aging Research Center, Division of Biotechnology, DGIST, Daegu 42988, Republic of Korea; Interdisciplinary Engineering Major, Department of Interdisciplinary Studies, DGIST, Daegu 42988, Republic of Korea
| | - Seung-Rock Lee
- Department of Biochemistry, Chonnam National University Medical School, Jeollanam-do 58128, Republic of Korea; Department of Biomedical Sciences, Research Center for Aging and Geriatrics, Research Institute of Medical Sciences, Chonnam National University Medical School, Gwangju 61469, Republic of Korea
| | - In Kyoung Lim
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 16499, Republic of Korea
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Hamilton DJ, Hein AE, Wuttke DS, Batey RT. The DNA binding high mobility group box protein family functionally binds RNA. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1778. [PMID: 36646476 PMCID: PMC10349909 DOI: 10.1002/wrna.1778] [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: 10/26/2022] [Revised: 12/22/2022] [Accepted: 12/27/2022] [Indexed: 01/18/2023]
Abstract
Nucleic acid binding proteins regulate transcription, splicing, RNA stability, RNA localization, and translation, together tailoring gene expression in response to stimuli. Upon discovery, these proteins are typically classified as either DNA or RNA binding as defined by their in vivo functions; however, recent evidence suggests dual DNA and RNA binding by many of these proteins. High mobility group box (HMGB) proteins have a DNA binding HMGB domain, act as transcription factors and chromatin remodeling proteins, and are increasingly understood to interact with RNA as means to regulate gene expression. Herein, multiple layers of evidence that the HMGB family are dual DNA and RNA binding proteins is comprehensively reviewed. For example, HMGB proteins directly interact with RNA in vitro and in vivo, are localized to RNP granules involved in RNA processing, and their protein interactors are enriched in RNA binding proteins involved in RNA metabolism. Importantly, in cell-based systems, HMGB-RNA interactions facilitate protein-protein interactions, impact splicing outcomes, and modify HMGB protein genomic or cellular localization. Misregulation of these HMGB-RNA interactions are also likely involved in human disease. This review brings to light that as a family, HMGB proteins are likely to bind RNA which is essential to HMGB protein biology. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Katahira J, Ohmae T, Yasugi M, Sasaki R, Itoh Y, Kohda T, Hieda M, Yokota Hirai M, Okamoto T, Miyamoto Y. Nsp14 of SARS-CoV-2 inhibits mRNA processing and nuclear export by targeting the nuclear cap-binding complex. Nucleic Acids Res 2023; 51:7602-7618. [PMID: 37260089 PMCID: PMC10415132 DOI: 10.1093/nar/gkad483] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 05/12/2023] [Accepted: 05/21/2023] [Indexed: 06/02/2023] Open
Abstract
To facilitate selfish replication, viruses halt host gene expression in various ways. The nuclear export of mRNA is one such process targeted by many viruses. SARS-CoV-2, the etiological agent of severe acute respiratory syndrome, also prevents mRNA nuclear export. In this study, Nsp14, a bifunctional viral replicase subunit, was identified as a novel inhibitor of mRNA nuclear export. Nsp14 induces poly(A)+ RNA nuclear accumulation and the dissolution/coalescence of nuclear speckles. Genome-wide gene expression analysis revealed the global dysregulation of splicing and 3'-end processing defects of replication-dependent histone mRNAs by Nsp14. These abnormalities were also observed in SARS-CoV-2-infected cells. A mutation introduced at the guanine-N7-methyltransferase active site of Nsp14 diminished these inhibitory activities. Targeted capillary electrophoresis-mass spectrometry analysis (CE-MS) unveiled the production of N7-methyl-GTP in Nsp14-expressing cells. Association of the nuclear cap-binding complex (NCBC) with the mRNA cap and subsequent recruitment of U1 snRNP and the stem-loop binding protein (SLBP) were impaired by Nsp14. These data suggest that the defects in mRNA processing and export arise from the compromise of NCBC function by N7-methyl-GTP, thus exemplifying a novel viral strategy to block host gene expression.
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Affiliation(s)
- Jun Katahira
- Laboratory of Cellular Molecular Biology, Graduate School of Veterinary Sciences, Osaka Metropolitan University, 1-58 Rinku-Orai-kita, Izumisano, Osaka 598-8531, Japan
| | - Tatsuya Ohmae
- Laboratory of Cellular Molecular Biology, Graduate School of Veterinary Sciences, Osaka Metropolitan University, 1-58 Rinku-Orai-kita, Izumisano, Osaka 598-8531, Japan
| | - Mayo Yasugi
- Laboratory of Veterinary Public Health, Graduate School of Veterinary Sciences, Osaka Metropolitan University, 1-58 Rinku-Orai-kita, Izumisano, Osaka 598-8531, Japan
| | - Ryosuke Sasaki
- RIKEN Center for Sustainable Resource Science, Mass Spectrometry and Microscopy Unit, 1-7-22 Suehiro. Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Yumi Itoh
- Institute for Advanced Co-Creation Studies, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tomoko Kohda
- Laboratory of Veterinary Epidemiology, Graduate School of Veterinary Sciences, Osaka Metropolitan University, 1-58 Rinku-Orai-kita, Izumisano, Osaka 598-8531, Japan
| | - Miki Hieda
- Department of Medical Technology, Ehime Prefectural University of Health Sciences, 543 Tobe-Cho Takaoda, Iyo, Ehime791-2102, Japan
| | - Masami Yokota Hirai
- RIKEN Center for Sustainable Resource Science, Mass Spectrometry and Microscopy Unit, 1-7-22 Suehiro. Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Toru Okamoto
- Institute for Advanced Co-Creation Studies, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yoichi Miyamoto
- Laboratory of Nuclear Transport Dynamics, National Institutes of Biomedical Innovation, Health, and Nutrition (NIBIOHN), 7-6-8 Saito Asagi, Ibaraki, Osaka 567-0085, Japan
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Guo J, Zhu Y, Ma X, Shang G, Liu B, Zhang K. Virus Infection and mRNA Nuclear Export. Int J Mol Sci 2023; 24:12593. [PMID: 37628773 PMCID: PMC10454920 DOI: 10.3390/ijms241612593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/29/2023] [Accepted: 08/03/2023] [Indexed: 08/27/2023] Open
Abstract
Gene expression in eukaryotes begins with transcription in the nucleus, followed by the synthesis of messenger RNA (mRNA), which is then exported to the cytoplasm for its translation into proteins. Along with transcription and translation, mRNA export through the nuclear pore complex (NPC) is an essential regulatory step in eukaryotic gene expression. Multiple factors regulate mRNA export and hence gene expression. Interestingly, proteins from certain types of viruses interact with these factors in infected cells, and such an interaction interferes with the mRNA export of the host cell in favor of viral RNA export. Thus, these viruses hijack the host mRNA nuclear export mechanism, leading to a reduction in host gene expression and the downregulation of immune/antiviral responses. On the other hand, the viral mRNAs successfully evade the host surveillance system and are efficiently exported from the nucleus to the cytoplasm for translation, which enables the continuation of the virus life cycle. Here, we present this review to summarize the mechanisms by which viruses suppress host mRNA nuclear export during infection, as well as the key strategies that viruses use to facilitate their mRNA nuclear export. These studies have revealed new potential antivirals that may be used to inhibit viral mRNA transport and enhance host mRNA nuclear export, thereby promoting host gene expression and immune responses.
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Affiliation(s)
- Jiayin Guo
- University of Chinese Academy of Sciences, Beijing 100049, China; (J.G.); (Y.Z.); (X.M.)
| | - Yaru Zhu
- University of Chinese Academy of Sciences, Beijing 100049, China; (J.G.); (Y.Z.); (X.M.)
| | - Xiaoya Ma
- University of Chinese Academy of Sciences, Beijing 100049, China; (J.G.); (Y.Z.); (X.M.)
| | - Guijun Shang
- Shanxi Provincial Key Laboratory of Protein Structure Determination, Shanxi Academy of Advanced Research and Innovation, Taiyuan 030012, China;
| | - Bo Liu
- Key Laboratory of Molecular Virology and Immunology, Chinese Academy of Sciences, Shanghai 200031, China
- Shanghai Huashen Institute of Microbes and Infections, Shanghai 200052, China
| | - Ke Zhang
- Key Laboratory of Molecular Virology and Immunology, Chinese Academy of Sciences, Shanghai 200031, China
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Crawford MW, Posch G, Cattin-Ortolá J, Topalidou I, Ailion M. Mutations in the NXF-1:NXT-1 mRNA export complex affect gene-expression driven by the hsp-16.41 promoter. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.000918. [PMID: 37583452 PMCID: PMC10423990 DOI: 10.17912/micropub.biology.000918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 07/29/2023] [Accepted: 07/30/2023] [Indexed: 08/17/2023]
Abstract
The NXF-1 : NXT-1 heterodimer is essential for the nuclear export of mRNA. Here we describe three new alleles of nxf-1 and one allele of nxt-1 isolated from a forward genetic screen. These mutations cause no apparent phenotype under normal growth conditions, but partially suppress the lethality caused by heat-shock induced expression of the PEEL-1 toxin from P hsp-16.41 :: peel-1 . There is also decreased expression of P hsp-16.41 ::eGFP in an nxf-1 mutant. We propose that NXF-1 : NXT-1 influences the expression of heat-shock activated genes due to a role in the recruitment of the hsp-16.41 promoter to the nuclear pore complex during heat-shock.
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Affiliation(s)
| | - Galen Posch
- Department of Biochemistry, University of Washington, Seattle, WA USA
| | | | - Irini Topalidou
- Department of Biochemistry, University of Washington, Seattle, WA USA
| | - Michael Ailion
- Department of Biochemistry, University of Washington, Seattle, WA USA
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11
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Chen SC, Xu CT, Chang CF, Chao TY, Lin CC, Fu PW, Yu CH. Optimization of 5'UTR to evade SARS-CoV-2 Nonstructural protein 1-directed inhibition of protein synthesis in cells. Appl Microbiol Biotechnol 2023; 107:2451-2468. [PMID: 36843199 PMCID: PMC9968647 DOI: 10.1007/s00253-023-12442-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 02/09/2023] [Accepted: 02/13/2023] [Indexed: 02/28/2023]
Abstract
Maximizing the expression level of therapeutic proteins in cells is the general goal for DNA/mRNA therapies. It is particularly challenging to achieve efficient protein expression in the cellular contexts with inhibited translation machineries, such as in the presence of cellular Nonstructural protein 1 (Nsp1) of coronaviruses (CoVs) that has been reported to inhibit overall protein synthesis of host genes and exogenously delivered mRNAs/DNAs. In this study, we thoroughly examined the sequence and structure contexts of viral and non-viral 5'UTRs that determine the protein expression levels of exogenously delivered DNAs and mRNAs in cells expressing SARS-CoV-2 Nsp1. It was found that high 5'-proximal A/U content promotes an escape from Nsp1-directed inhibition of protein synthesis and results in selective protein expression. Furthermore, 5'-proximal Cs were found to significantly enhance the protein expression in an Nsp1-dependent manner, while Gs located at a specific window close to the 5'-end counteract such enhancement. The distinct protein expression levels resulted from different 5'UTRs were found correlated to Nsp1-induced mRNA degradations. These findings ultimately enabled rational designs for optimized 5'UTRs that lead to strong expression of exogenous proteins regardless of the translationally repressive Nsp1. On the other hand, we have also identified several 5'-proximal sequences derived from host genes that are capable of mediating the escapes. These results provided novel perspectives to the optimizations of 5'UTRs for DNA/mRNA therapies and/or vaccinations, as well as shedding light on the potential host escapees from Nsp1-directed translational shutoffs. KEY POINTS: • The 5'-proximal SL1 and 5a/b derived from SARS-CoV-2 genomic RNA promote exogenous protein synthesis in cells expressing Nsp1 comparing with non-specific 5'UTRs. • Specific 5'-proximal sequence contexts are the key determinants of the escapes from Nsp1-directed translational repression and thereby enhance protein expressions. • Systematic mutagenesis identified optimized 5'UTRs that strongly enhance protein expression and promote resistance to Nsp1-induced translational repression and RNA degradation.
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Affiliation(s)
- Shih-Cheng Chen
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- National Institute of Cancer Research, National Health Research Institutes, New Taipei, Taiwan
| | - Cui-Ting Xu
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chuan-Fu Chang
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Ting-Yu Chao
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chia-Chi Lin
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Pei-Wen Fu
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chien-Hung Yu
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
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12
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El-Tanani M, Nsairat H, Mishra V, Mishra Y, Aljabali AAA, Serrano-Aroca Á, Tambuwala MM. Ran GTPase and Its Importance in Cellular Signaling and Malignant Phenotype. Int J Mol Sci 2023; 24:ijms24043065. [PMID: 36834476 PMCID: PMC9968026 DOI: 10.3390/ijms24043065] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 02/08/2023] Open
Abstract
Ran is a member of the Ras superfamily of proteins, which primarily regulates nucleocytoplasmic trafficking and mediates mitosis by regulating spindle formation and nuclear envelope (NE) reassembly. Therefore, Ran is an integral cell fate determinant. It has been demonstrated that aberrant Ran expression in cancer is a result of upstream dysregulation of the expression of various factors, such as osteopontin (OPN), and aberrant activation of various signaling pathways, including the extracellular-regulated kinase/mitogen-activated protein kinase (ERK/MEK) and phosphatidylinositol 3-kinase/Protein kinase B (PI3K/Akt) pathways. In vitro, Ran overexpression has severe effects on the cell phenotype, altering proliferation, adhesion, colony density, and invasion. Therefore, Ran overexpression has been identified in numerous types of cancer and has been shown to correlate with tumor grade and the degree of metastasis present in various cancers. The increased malignancy and invasiveness have been attributed to multiple mechanisms. Increased dependence on Ran for spindle formation and mitosis is a consequence of the upregulation of these pathways and the ensuing overexpression of Ran, which increases cellular dependence on Ran for survival. This increases the sensitivity of cells to changes in Ran concentration, with ablation being associated with aneuploidy, cell cycle arrest, and ultimately, cell death. It has also been demonstrated that Ran dysregulation influences nucleocytoplasmic transport, leading to transcription factor misallocation. Consequently, patients with tumors that overexpress Ran have been shown to have a higher malignancy rate and a shorter survival time compared to their counterparts.
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Affiliation(s)
- Mohamed El-Tanani
- Pharmacological and Diagnostic Research Centre, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman 19328, Jordan
- Correspondence:
| | - Hamdi Nsairat
- Pharmacological and Diagnostic Research Centre, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman 19328, Jordan
| | - Vijay Mishra
- School of Pharmaceutical Sciences, Lovely Professional University, Phagwara 144411, India
| | - Yachana Mishra
- Department of Zoology, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara 144411, India
| | - Alaa A. A. Aljabali
- Department of Pharmaceutics & Pharmaceutical Technology, Yarmouk University, Irbid 21163, Jordan
| | - Ángel Serrano-Aroca
- Biomaterials and Bioengineering Laboratory, Centro de Investigación Traslacional San Alberto Magno, Universidad Católica de Valencia San Vicente Mártir, c/Guillem de Castro 94, 46001 Valencia, Spain
| | - Murtaza M. Tambuwala
- Lincoln Medical School, University of Lincoln, Brayford Pool, Lincoln LN6 7TS, UK
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13
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Jiang Y, Zhong S, He S, Weng J, Liu L, Ye Y, Chen H. Biomarkers (mRNAs and non-coding RNAs) for the diagnosis and prognosis of rheumatoid arthritis. Front Immunol 2023; 14:1087925. [PMID: 36817438 PMCID: PMC9929281 DOI: 10.3389/fimmu.2023.1087925] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 01/09/2023] [Indexed: 02/04/2023] Open
Abstract
In recent years, diagnostic and therapeutic approaches for rheumatoid arthritis (RA) have continued to improve. However, in the advanced stages of the disease, patients are unable to achieve long-term clinical remission and often suffer from systemic multi-organ damage and severe complications. Patients with RA usually have no overt clinical manifestations in the early stages, and by the time a definitive diagnosis is made, the disease is already at an advanced stage. RA is diagnosed clinically and with laboratory tests, including the blood markers C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) and the autoantibodies rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPA). However, the presence of RF and ACPA autoantibodies is associated with aggravated disease, joint damage, and increased mortality, and these autoantibodies have low specificity and sensitivity. The etiology of RA is unknown, with the pathogenesis involving multiple factors and clinical heterogeneity. The early diagnosis, subtype classification, and prognosis of RA remain challenging, and studies to develop minimally invasive or non-invasive biomarkers in the form of biofluid biopsies are becoming more common. Non-coding RNA (ncRNA) molecules are composed of long non-coding RNAs, small nucleolar RNAs, microRNAs, and circular RNAs, which play an essential role in disease onset and progression and can be used in the early diagnosis and prognosis of RA. In this review of the diagnostic and prognostic approaches to RA disease, we provide an overview of the current knowledge on the subject, focusing on recent advances in mRNA-ncRNA as diagnostic and prognostic biomarkers from the biofluid to the tissue level.
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Affiliation(s)
- Yong Jiang
- Department of Radiology, Guangzhou Panyu Central Hospital, Guangzhou, China.,Graduate School, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Shuxin Zhong
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Jinan University, Guangzhou, China
| | - Shenghua He
- The Fourth Clinical Medical College of Guangzhou University of Chinese Medicine, Shenzhen, China
| | - Juanling Weng
- The Fourth Clinical Medical College of Guangzhou University of Chinese Medicine, Shenzhen, China
| | - Lijin Liu
- The Fourth Clinical Medical College of Guangzhou University of Chinese Medicine, Shenzhen, China
| | - Yufeng Ye
- Department of Radiology, Guangzhou Panyu Central Hospital, Guangzhou, China
| | - Hanwei Chen
- Department of Radiology, Guangzhou Panyu Central Hospital, Guangzhou, China.,Department of Radiology, GuangzhouPanyu Health Management Center (Panyu Rehabilitation Hospital), Guangzhou, China
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14
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Tough Way In, Tough Way Out: The Complex Interplay of Host and Viral Factors in Nucleocytoplasmic Trafficking during HIV-1 Infection. Viruses 2022; 14:v14112503. [PMID: 36423112 PMCID: PMC9696704 DOI: 10.3390/v14112503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 11/08/2022] [Accepted: 11/09/2022] [Indexed: 11/16/2022] Open
Abstract
Human immunodeficiency virus-1 (HIV-1) is a retrovirus that integrates its reverse-transcribed genome as proviral DNA into the host genome to establish a successful infection. The viral genome integration requires safeguarding the subviral complexes, reverse transcription complex (RTC) and preintegration complex (PIC), in the cytosol from degradation, presumably effectively secured by the capsid surrounding these complexes. An intact capsid, however, is a large structure, which raises concerns about its translocation from cytoplasm to nucleus crossing the nuclear membrane, guarded by complex nuclear pore structures, which do not allow non-specific transport of large molecules. In addition, the generation of new virions requires the export of incompletely processed viral RNA from the nucleus to the cytoplasm, an event conventionally not permitted through mammalian nuclear membranes. HIV-1 has evolved multiple mechanisms involving redundant host pathways by liaison with the cell's nucleocytoplasmic trafficking system, failure of which would lead to the collapse of the infection cycle. This review aims to assemble the current developments in temporal and spatial events governing nucleocytoplasmic transport of HIV-1 factors. Discoveries are anticipated to serve as the foundation for devising host-directed therapies involving selective abolishment of the critical interactomes between viral proteins and their host equivalents.
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15
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Zhang H, Li X, Song R, Zhan Z, Zhao F, Li Z, Jiang D. Cap-binding complex assists RNA polymerase II transcription in plant salt stress response. PLANT, CELL & ENVIRONMENT 2022; 45:2780-2793. [PMID: 35773782 DOI: 10.1111/pce.14388] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 05/14/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
Adaptive response to stress involves an extensive reprogramming of gene expression. Under stressful conditions, the induction of efficient changes in messenger RNA (mRNA) production is crucial for maximized plant survival. Transcription and pre-mRNA processing are two closely related steps in mRNA biogenesis, yet how they are controlled in plant stress response remains elusive. Here, we show that the Arabidopsis nuclear cap-binding complex (CBC) component CBP20 directly interacts with ELF7, a subunit of the transcription elongation factor RNA Pol II-associated factor 1 complex (PAF1c) to promote RNA Pol II transcription in plant response to salt stress. CBP20 and ELF7 coregulate the expression of a large number of genes including those crucial for salt tolerance. Both CBP20 and ELF7 are required for enhanced RNA Pol II elongation at salt-activated genes. Though CBP20 also regulates intron splicing, this function is largely independent of ELF7. Our study reveals the function of an RNA processing regulator CBC in assisting efficient RNA Pol II transcription and pinpoints the complex roles of CBC on mRNA production in plant salt stress resistance.
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Affiliation(s)
- Huairen Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
| | - Xiaoyi Li
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ruitian Song
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhenping Zhan
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Fengyue Zhao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zicong Li
- Ministry of Education Key Laboratory of Plant Development and Environmental Adaption Biology, School of Life Sciences, Shandong University, Qingdao, China
| | - Danhua Jiang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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16
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Miwa T, Ohtani K, Inoue K, Sakamoto H. The germ cell-specific TAP-like protein NXF-2 forms a novel granular structure and is required for tra-2 3'UTR-dependent mRNA export in Caenorhabditis elegans. Genes Cells 2022; 27:621-628. [PMID: 35950937 DOI: 10.1111/gtc.12978] [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: 07/04/2022] [Revised: 08/04/2022] [Accepted: 08/07/2022] [Indexed: 11/29/2022]
Abstract
TAP is a general mRNA export receptor and is highly conserved among eukaryotes. The nematode Caenorhabditis elegans has another TAP-like protein, NXF-2, but little is known about its function. In this study, we show that NXF-2 is specifically expressed in germ cells and forms a novel granular structure that is different from that of P granules and that NXF-2 granules are anchored to the nuclear periphery in the mitotic region of the hermaphrodite gonad. In contrast, NXF-2 granules are released within the whole cytoplasm in the meiotic region, where the feminization gene tra-2 starts to function. Both inhibition of XPO-1 (an ortholog of the export receptor CRM1) and mutation of the nuclear export signal of NXF-2 caused the release of NXF-2 granules from the nuclear periphery, indicating that anchoring of NXF-2 granules depends on XPO-1 function. Moreover, inhibition of NXF-2 resulted in a substantial nuclear accumulation of the reporter mRNA carrying the tra-2 3'UTR. These results suggest that, together with XPO-1, NXF-2 exports and anchors tra-2 mRNA to the nuclear periphery to avoid precocious translation until the germ cells reach the meiotic region, thereby contributing to the regulation of tra-2 mRNA expression. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Takashi Miwa
- Biology, Kobe University Graduate School of Science Faculty of Science, Grad. Sch. Sci. Tech.1-1 Rokkodai, Nada-ku, Kobe Hyogo, Japan
| | - Keigo Ohtani
- Biology, Kobe University Graduate School of Science Faculty of Science, Grad. Sch. Sci. Tech.1-1 Rokkodai, Nada-ku, Kobe Hyogo, Japan
| | - Kunio Inoue
- Biology, Kobe University Graduate School of Science Faculty of Science, Grad. Sch. Sci. Tech.1-1 Rokkodai, Nada-ku, Kobe Hyogo, Japan
| | - Hiroshi Sakamoto
- Biology, Kobe University Graduate School of Science Faculty of Science, Grad. Sch. Sci. Tech.1-1 Rokkodai, Nada-ku, Kobe Hyogo, Japan
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17
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Pakhomova T, Moshareva M, Vasilkova D, Zatsepin T, Dontsova O, Rubtsova M. Role of RNA Biogenesis Factors in the Processing and Transport of Human Telomerase RNA. Biomedicines 2022; 10:biomedicines10061275. [PMID: 35740297 PMCID: PMC9219725 DOI: 10.3390/biomedicines10061275] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 05/26/2022] [Accepted: 05/27/2022] [Indexed: 11/21/2022] Open
Abstract
Telomerase RNA has long been considered to be a noncoding component of telomerase. However, the expression of the telomerase RNA gene is not always associated with telomerase activity. The existence of distinct TERC gene expression products possessing different functions were demonstrated recently. During biogenesis, hTR is processed by distinct pathways and localized in different cell compartments, depending on whether it functions as a telomerase complex component or facilitates antistress activities as a noncoding RNA, in which case it is either processed in the mitochondria or translated. In order to identify the factors responsible for the appearance and localization of the exact isoform of hTR, we investigated the roles of the factors regulating transcription DSIF (Spt5) and NELF-E; exosome-attracting factors ZCCHC7, ZCCHC8, and ZFC3H1; ARS2, which attracts processing and transport factors; and transport factor PHAX during the biogenesis of hTR. The data obtained revealed that ZFC3H1 participates in hTR biogenesis via pathways related to the polyadenylated RNA degradation mechanism. The data revealed essential differences that are important for understanding hTR biogenesis and that are interesting for further investigations of new, therapeutically significant targets.
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Affiliation(s)
- Tatiana Pakhomova
- Department of Chemistry, A. N. Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia; (T.P.); (M.M.); (D.V.); (O.D.)
| | - Maria Moshareva
- Department of Chemistry, A. N. Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia; (T.P.); (M.M.); (D.V.); (O.D.)
| | - Daria Vasilkova
- Department of Chemistry, A. N. Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia; (T.P.); (M.M.); (D.V.); (O.D.)
| | - Timofey Zatsepin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russia;
| | - Olga Dontsova
- Department of Chemistry, A. N. Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia; (T.P.); (M.M.); (D.V.); (O.D.)
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russia;
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Skolkovo, Moscow 121205, Russia
| | - Maria Rubtsova
- Department of Chemistry, A. N. Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia; (T.P.); (M.M.); (D.V.); (O.D.)
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russia;
- Correspondence:
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18
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Function of the Nuclear Transport Machinery in Maintaining the Distinctive Compositions of the Nucleus and Cytoplasm. Int J Mol Sci 2022; 23:ijms23052578. [PMID: 35269721 PMCID: PMC8910404 DOI: 10.3390/ijms23052578] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/13/2022] [Accepted: 02/23/2022] [Indexed: 02/06/2023] Open
Abstract
Although the separation of transcription and translation, mediated by the nuclear envelope, is the defining characteristic of Eukaryotes, the barrier between the nuclear and cytoplasmic compartments needs to be semipermeable to enable material to be moved between them. Moreover, each compartment needs to have a distinctive complement of macromolecules to mediate specific functions and so movement between them needs to be controlled. This is achieved through the selective active transport of macromolecules through the nuclear pores that stud the nuclear envelope, and which serve as a conduit between these compartments. Nuclear pores are huge cylindrical macromolecular assemblies and are constructed from the order of 30 different proteins called nucleoporins. Nuclear pores have a central transport channel that is filled with a dense network of natively unfolded portions of many different nuclear pore proteins (nucleoporins or nups). This network generates a barrier that impedes, but does not entirely prevent, the diffusion of many macromolecules through the pores. The rapid movement of a range of proteins and RNAs through the pores is mediated by a range of transport factors that bind their cargo in one compartment and release it in the other. However, although as their size increases the diffusion of macromolecules through nuclear pores is progressively impaired, additional mechanisms, including the binding of some macromolecules to immobile components of each compartment and also the active removal of macromolecules from the inappropriate compartment, are needed to fully maintain the distinctive compositions of each compartment.
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19
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Banerjee P, Markande S, Kalarikkal M, Joseph J. SUMOylation modulates the function of DDX19 in mRNA export. J Cell Sci 2022; 135:274424. [PMID: 35080244 DOI: 10.1242/jcs.259449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 01/13/2022] [Indexed: 11/20/2022] Open
Abstract
Nuclear export of mRNAs is a critical regulatory step in eukaryotic gene expression. The mRNA transcript undergoes extensive processing, and is loaded with a set of RNA-binding proteins (RBPs) to form export-competent messenger ribonucleoprotein particles (mRNPs) in the nucleus. During the transit of mRNPs through the nuclear pore complex (NPC), the DEAD-box ATPase - DDX19 - remodels mRNPs at the cytoplasmic side of the NPC, by removing a subset of RNA-binding proteins to terminate mRNP export. This requires the RNA-dependent ATPase activity of DDX19 and its dynamic interactions with Gle1 and Nup214. However, the regulatory mechanisms underlying these interactions are unclear. We find that DDX19 gets covalently attached with a small ubiquitin-like modifier (SUMO) at lysine 26, which enhances its interaction with Gle1. Furthermore, a SUMOylation-defective mutant of human DDX19B, K26R, failed to provide a complete rescue of the mRNA export defect caused by DDX19 depletion. Collectively, our results suggest that SUMOylation fine-tunes the function of DDX19 in mRNA export by regulating its interaction with Gle1. This study identifies SUMOylation of DDX19 as a modulatory mechanism during the mRNA export process.
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Affiliation(s)
- Poulomi Banerjee
- National Centre for Cell Science, S. P. Pune University Campus, Pune - 411007, Maharashtra State, India
| | - Shubha Markande
- National Centre for Cell Science, S. P. Pune University Campus, Pune - 411007, Maharashtra State, India
| | - Misha Kalarikkal
- National Centre for Cell Science, S. P. Pune University Campus, Pune - 411007, Maharashtra State, India
| | - Jomon Joseph
- National Centre for Cell Science, S. P. Pune University Campus, Pune - 411007, Maharashtra State, India
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20
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Wang S, Sun S. Measuring Repeat-Associated Non-AUG (RAN) Translation. Methods Mol Biol 2022; 2428:113-132. [PMID: 35171477 DOI: 10.1007/978-1-0716-1975-9_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Expansions of short nucleotide repeats account for more than 50 neurological or neuromuscular diseases. Many repeat expansion-containing RNAs can generate toxic repeat proteins through repeat-associated non-AUG (RAN) translation in all the reading frames. Understanding how RAN translation occurs and what cellular factors regulate this process will help decipher the basic mechanism of the molecular process and disease pathogenesis. Using reporter systems to quantitatively measure RAN translation provides a platform to examine candidate genes/pathways and screen for modifiers of this non-canonical pathway. In this chapter, we describe the dual-luciferase reporter system to measure RAN translation using C9ORF72 GGGGCCexp as an example, which is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
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Affiliation(s)
- Shaopeng Wang
- Department of Pathology, Physiology, Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shuying Sun
- Department of Pathology, Physiology, Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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21
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Schneider-Lunitz V, Ruiz-Orera J, Hubner N, van Heesch S. Multifunctional RNA-binding proteins influence mRNA abundance and translational efficiency of distinct sets of target genes. PLoS Comput Biol 2021; 17:e1009658. [PMID: 34879078 PMCID: PMC8687540 DOI: 10.1371/journal.pcbi.1009658] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 12/20/2021] [Accepted: 11/18/2021] [Indexed: 12/12/2022] Open
Abstract
RNA-binding proteins (RBPs) can regulate more than a single aspect of RNA metabolism. We searched for such previously undiscovered multifunctionality within a set of 143 RBPs, by defining the predictive value of RBP abundance for the transcription and translation levels of known RBP target genes across 80 human hearts. This led us to newly associate 27 RBPs with cardiac translational regulation in vivo. Of these, 21 impacted both RNA expression and translation, albeit for virtually independent sets of target genes. We highlight a subset of these, including G3BP1, PUM1, UCHL5, and DDX3X, where dual regulation is achieved through differential affinity for target length, by which separate biological processes are controlled. Like the RNA helicase DDX3X, the known splicing factors EFTUD2 and PRPF8—all identified as multifunctional RBPs by our analysis—selectively influence target translation rates depending on 5’ UTR structure. Our analyses identify dozens of RBPs as being multifunctional and pinpoint potential novel regulators of translation, postulating unanticipated complexity of protein-RNA interactions at consecutive stages of gene expression. The lifecycle of an RNA molecule is controlled by hundreds of proteins that can bind RNA, also known as RNA-binding proteins (RBPs). These proteins recognize landing sites within the RNA and guide the RNA’s transcription from DNA, its processing into a mature messenger RNA, its translation into protein, or its degradation once the RNA is no longer needed. Although we now mechanistically understand how certain RBPs regulate these processes, for many RBP-target interactions the consequences imposed by RNA binding are not well understood. For 143 RBPs with known RNA binding positions, the authors of the current study investigated how RNA molecules responded to fluctuations in the expression levels of these RBPs, across each of 80 human hearts. Using statistical approaches, they could show that many RBPs influenced stages of the RNA lifecycle that they were not known to be involved in. Some RBPs turned out to be true "all-rounders" of RNA metabolism: they controlled the RNA transcript levels of some genes, whereas they influenced the translation rates of others. This unexpected multifunctionality unveiled previously hidden aspects of the everyday RNA-binding protein working life.
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Affiliation(s)
- Valentin Schneider-Lunitz
- Cardiovascular and Metabolic Sciences, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
| | - Jorge Ruiz-Orera
- Cardiovascular and Metabolic Sciences, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
| | - Norbert Hubner
- Cardiovascular and Metabolic Sciences, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
- Charité-Universitätsmedizin, Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Berlin, Berlin, Germany
- * E-mail: (NH); (SvH)
| | - Sebastiaan van Heesch
- Princess Máxima Center for Pediatric Oncology, Utrecht, The Netherlands
- * E-mail: (NH); (SvH)
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22
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To export, or not to export: how nuclear export factor variants resolve Piwi's dilemma. Biochem Soc Trans 2021; 49:2073-2079. [PMID: 34643228 DOI: 10.1042/bst20201171] [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: 03/29/2021] [Revised: 09/06/2021] [Accepted: 09/15/2021] [Indexed: 11/17/2022]
Abstract
Piwi-interacting RNAs (piRNAs) defend animal gonads by guiding PIWI-clade Argonaute proteins to silence transposons. The nuclear Piwi/piRNA complexes confer transcriptional repression of transposons, which is accompanied with heterochromatin formation at target loci. On the other hand, piRNA clusters, genomic loci that transcribe piRNA precursors composed of transposon fragments, are often recognized by piRNAs to define their heterochromatic identity. Therefore, Piwi/piRNA complexes must resolve this conundrum of silencing transposons while allowing the expression of piRNA precursors, at least in Drosophila germlines. This review is focused on recent advances how the piRNA pathway deals with this genetic conflict.
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23
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Lisy S, Rothamel K, Ascano M. RNA Binding Proteins as Pioneer Determinants of Infection: Protective, Proviral, or Both? Viruses 2021; 13:v13112172. [PMID: 34834978 PMCID: PMC8625426 DOI: 10.3390/v13112172] [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: 09/27/2021] [Revised: 10/22/2021] [Accepted: 10/23/2021] [Indexed: 12/18/2022] Open
Abstract
As the first intracellular host factors that directly interact with the genomes of RNA viruses, RNA binding proteins (RBPs) have a profound impact on the outcome of an infection. Recent discoveries brought about by new methodologies have led to an unprecedented ability to peer into the earliest events between viral RNA and the RBPs that act upon them. These discoveries have sparked a re-evaluation of current paradigms surrounding RBPs and post-transcriptional gene regulation. Here, we highlight questions that have bloomed from the implementation of these novel approaches. Canonical RBPs can impact the fates of both cellular and viral RNA during infection, sometimes in conflicting ways. Noncanonical RBPs, some of which were first characterized via interactions with viral RNA, may encompass physiological roles beyond viral pathogenesis. We discuss how these RBPs might discriminate between an RNA of either cellular or viral origin and thus exert either pro- or antiviral effects—which is a particular challenge as viruses contain mechanisms to mimic molecular features of cellular RNA.
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Affiliation(s)
- Samantha Lisy
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; (S.L.); (K.R.)
| | - Katherine Rothamel
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; (S.L.); (K.R.)
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92037, USA
| | - Manuel Ascano
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; (S.L.); (K.R.)
- Correspondence: ; Tel.: +1-615-875-8714
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24
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Niikura M, Fukutomi T, Mitobe J, Kobayashi F. Roles and Cellular Localization of GBP2 and NAB2 During the Blood Stage of Malaria Parasites. Front Cell Infect Microbiol 2021; 11:737457. [PMID: 34604117 PMCID: PMC8479154 DOI: 10.3389/fcimb.2021.737457] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 08/24/2021] [Indexed: 12/03/2022] Open
Abstract
The quality control and export of mRNA by RNA-binding proteins are necessary for the survival of malaria parasites, which have complex life cycles. Nuclear poly(A) binding protein 2 (NAB2), THO complex subunit 4 (THO4), nucleolar protein 3 (NPL3), G-strand binding protein 2 (GBP2) and serine/arginine-rich splicing factor 1 (SR1) are involved in nuclear mRNA export in malaria parasites. However, their roles in asexual and sexual development, and in cellular localization, are not fully understood. In this study using the rodent malaria parasite, Plasmodium berghei, we found that NAB2 and SR1, but not THO4, NPL3 or GBP2, played essential roles in the asexual development of malaria parasites. By contrast, GBP2 but not NPL3 was involved in male and female gametocyte production. THO4 was involved in female gametocyte production, but had a lower impact than GBP2. In this study, we focused on GBP2 and NAB2, which play important roles in the sexual and asexual development of malaria parasites, respectively, and examined their cellular localization. GBP2 localized to both the nucleus and cytoplasm of malaria parasites. Using immunoprecipitation coupled to mass spectrometry (IP-MS), GBP2 interacted with the proteins ALBA4, DOZI, and CITH, which play roles in translational repression. IP-MS also revealed that phosphorylated adapter RNA export protein (PHAX) domain-containing protein, an adaptor protein for exportin-1, also interacted with GBP2, implying that mRNA export occurs via the PHAX domain-containing protein pathway in malaria parasites. Live-cell fluorescence imaging revealed that NAB2 localized at the nuclear periphery. Moreover, IP-MS indicated that NAB2 interacted with transportin. RNA immunoprecipitation coupled to RNA sequencing revealed that NAB2 bound directly to 143 mRNAs, including those encoding 40S and 60S ribosomal proteins. Our findings imply that malaria parasites use an evolutionarily ancient mechanism conserved throughout eukaryotic evolution.
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Affiliation(s)
- Mamoru Niikura
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan
| | - Toshiyuki Fukutomi
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
| | - Jiro Mitobe
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan
| | - Fumie Kobayashi
- Department of Environmental Science, School of Life and Environmental Science, Azabu University, Kanagawa, Japan
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25
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Francette AM, Tripplehorn SA, Arndt KM. The Paf1 Complex: A Keystone of Nuclear Regulation Operating at the Interface of Transcription and Chromatin. J Mol Biol 2021; 433:166979. [PMID: 33811920 PMCID: PMC8184591 DOI: 10.1016/j.jmb.2021.166979] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/21/2021] [Accepted: 03/24/2021] [Indexed: 12/14/2022]
Abstract
The regulation of transcription by RNA polymerase II is closely intertwined with the regulation of chromatin structure. A host of proteins required for the disassembly, reassembly, and modification of nucleosomes interacts with Pol II to aid its movement and counteract its disruptive effects on chromatin. The highly conserved Polymerase Associated Factor 1 Complex, Paf1C, travels with Pol II and exerts control over transcription elongation and chromatin structure, while broadly impacting the transcriptome in both single cell and multicellular eukaryotes. Recent studies have yielded exciting new insights into the mechanisms by which Paf1C regulates transcription elongation, epigenetic modifications, and post-transcriptional steps in eukaryotic gene expression. Importantly, these functional studies are now supported by an extensive foundation of high-resolution structural information, providing intimate views of Paf1C and its integration into the larger Pol II elongation complex. As a global regulatory factor operating at the interface between chromatin and transcription, the impact of Paf1C is broad and its influence reverberates into other domains of nuclear regulation, including genome stability, telomere maintenance, and DNA replication.
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Affiliation(s)
- Alex M Francette
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Sarah A Tripplehorn
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Karen M Arndt
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States.
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26
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Park Y, Park J, Hwang HJ, Kim L, Jeong K, Song HK, Rufener SC, Mühlemann O, Kim YK. Translation mediated by the nuclear cap-binding complex is confined to the perinuclear region via a CTIF-DDX19B interaction. Nucleic Acids Res 2021; 49:8261-8276. [PMID: 34232997 PMCID: PMC8373075 DOI: 10.1093/nar/gkab579] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 06/08/2021] [Accepted: 06/23/2021] [Indexed: 12/29/2022] Open
Abstract
Newly synthesized mRNA is translated during its export through the nuclear pore complex, when its 5′-cap structure is still bound by the nuclear cap-binding complex (CBC), a heterodimer of cap-binding protein (CBP) 80 and CBP20. Despite its critical role in mRNA surveillance, the mechanism by which CBC-dependent translation (CT) is regulated remains unknown. Here, we demonstrate that the CT initiation factor (CTIF) is tethered in a translationally incompetent manner to the perinuclear region by the DEAD-box helicase 19B (DDX19B). DDX19B hands over CTIF to CBP80, which is associated with the 5′-cap of a newly exported mRNA. The resulting CBP80–CTIF complex then initiates CT in the perinuclear region. We also show that impeding the interaction between CTIF and DDX19B leads to uncontrolled CT throughout the cytosol, consequently dysregulating nonsense-mediated mRNA decay. Altogether, our data provide molecular evidence supporting the importance of tight control of local translation in the perinuclear region.
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Affiliation(s)
- Yeonkyoung Park
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Joori Park
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hyun Jung Hwang
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Leehyeon Kim
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Kwon Jeong
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hyun Kyu Song
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Simone C Rufener
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Yoon Ki Kim
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841, Republic of Korea.,Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
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27
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Shen Q, Wang YE, Palazzo AF. Crosstalk between nucleocytoplasmic trafficking and the innate immune response to viral infection. J Biol Chem 2021; 297:100856. [PMID: 34097873 PMCID: PMC8254040 DOI: 10.1016/j.jbc.2021.100856] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 05/24/2021] [Accepted: 06/03/2021] [Indexed: 12/16/2022] Open
Abstract
The nuclear pore complex is the sole gateway connecting the nucleoplasm and cytoplasm. In humans, the nuclear pore complex is one of the largest multiprotein assemblies in the cell, with a molecular mass of ∼110 MDa and consisting of 8 to 64 copies of about 34 different nuclear pore proteins, termed nucleoporins, for a total of 1000 subunits per pore. Trafficking events across the nuclear pore are mediated by nuclear transport receptors and are highly regulated. The nuclear pore complex is also used by several RNA viruses and almost all DNA viruses to access the host cell nucleoplasm for replication. Viruses hijack the nuclear pore complex, and nuclear transport receptors, to access the nucleoplasm where they replicate. In addition, the nuclear pore complex is used by the cell innate immune system, a network of signal transduction pathways that coordinates the first response to foreign invaders, including viruses and other pathogens. Several branches of this response depend on dynamic signaling events that involve the nuclear translocation of downstream signal transducers. Mounting evidence has shown that these signaling cascades, especially those steps that involve nucleocytoplasmic trafficking events, are targeted by viruses so that they can evade the innate immune system. This review summarizes how nuclear pore proteins and nuclear transport receptors contribute to the innate immune response and highlights how viruses manipulate this cellular machinery to favor infection. A comprehensive understanding of nuclear pore proteins in antiviral innate immunity will likely contribute to the development of new antiviral therapeutic strategies.
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Affiliation(s)
- Qingtang Shen
- School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
| | - Yifan E Wang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Alexander F Palazzo
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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28
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ARS2/SRRT: at the nexus of RNA polymerase II transcription, transcript maturation and quality control. Biochem Soc Trans 2021; 49:1325-1336. [PMID: 34060620 DOI: 10.1042/bst20201008] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/04/2021] [Accepted: 05/06/2021] [Indexed: 01/26/2023]
Abstract
ARS2/SRRT is an essential eukaryotic protein that has emerged as a critical factor in the sorting of functional from non-functional RNA polymerase II (Pol II) transcripts. Through its interaction with the Cap Binding Complex (CBC), it associates with the cap of newly made RNAs and acts as a hub for competitive exchanges of protein factors that ultimately determine the fate of the associated RNA. The central position of the protein within the nuclear gene expression machinery likely explains why its depletion causes a broad range of phenotypes, yet an exact function of the protein remains elusive. Here, we consider the literature on ARS2/SRRT with the attempt to garner the threads into a unifying working model for ARS2/SRRT function at the nexus of Pol II transcription, transcript maturation and quality control.
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29
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Chan QWT, Rogalski J, Moon KM, Foster LJ. The application of forensic proteomics to identify an unknown snake venom in a deceased toddler. Forensic Sci Int 2021; 323:110820. [PMID: 33984813 DOI: 10.1016/j.forsciint.2021.110820] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 04/23/2021] [Accepted: 04/26/2021] [Indexed: 10/21/2022]
Abstract
Proteomics is the global analysis of proteins in a sample, and its methodologies are commonly applied in life science research. Despite its wide applicability however, proteomics is rarely used as a tool in criminal investigations. Here we present a case where the technique provided key evidence in a case that involved the death of a two-year old girl. The defendant was known to keep exotic snakes, including several venomous species, which led the coroner to probe whether there could be snake venom in the blood of the deceased. One major challenge of the investigation was the overwhelming presence of several blood proteins, such as apolipoprotein and complement proteins, which hinders the detection of less abundant analytes. In a counter-acting strategy, a combination of immunodepletion and fractionation methods was used; the sample was then submitted to tandem mass spectrometry for peptide identification. Using this strategy, 15,000 peptides could be sequenced. However, the subsequent challenge was to differentiate between human and snake proteins, given the genetic similarities that are shared by the two vertebrate species. After a thorough bioinformatics search and manual inspection, we found that<1% of the sequenced peptides could be matched unequivocally to snake proteins, including a well-known venom component, phospholipase A2. This evidence, in part, led to a court-issued search warrant of the defendant's home, followed by his arrest and an eventual guilty plea with formal sentencing to 18 months in prison. The work outlined here is an example of how proteomics technology can help to expand the toolkit for molecular forensics.
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Affiliation(s)
- Queenie W T Chan
- Michael Smith Laboratories and Department of Biochemistry & Molecular Biology, University of British Columbia, 2185 E Mall, Vancouver, BC V6T 1Z4, Canada
| | - Jason Rogalski
- Michael Smith Laboratories and Department of Biochemistry & Molecular Biology, University of British Columbia, 2185 E Mall, Vancouver, BC V6T 1Z4, Canada
| | - Kyung-Mee Moon
- Michael Smith Laboratories and Department of Biochemistry & Molecular Biology, University of British Columbia, 2185 E Mall, Vancouver, BC V6T 1Z4, Canada
| | - Leonard J Foster
- Michael Smith Laboratories and Department of Biochemistry & Molecular Biology, University of British Columbia, 2185 E Mall, Vancouver, BC V6T 1Z4, Canada.
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30
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Ding B, Tang Y, Ma S, Akter M, Liu ML, Zang T, Zhang CL. Disease Modeling with Human Neurons Reveals LMNB1 Dysregulation Underlying DYT1 Dystonia. J Neurosci 2021; 41:2024-2038. [PMID: 33468570 PMCID: PMC7939088 DOI: 10.1523/jneurosci.2507-20.2020] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 12/23/2020] [Accepted: 12/30/2020] [Indexed: 02/08/2023] Open
Abstract
DYT1 dystonia is a hereditary neurologic movement disorder characterized by uncontrollable muscle contractions. It is caused by a heterozygous mutation in Torsin A (TOR1A), a gene encoding a membrane-embedded ATPase. While animal models provide insights into disease mechanisms, significant species-dependent differences exist since animals with the identical heterozygous mutation fail to show pathology. Here, we model DYT1 by using human patient-specific cholinergic motor neurons (MNs) that are generated through either direct conversion of patients' skin fibroblasts or differentiation of induced pluripotent stem cells (iPSCs). These human MNs with the heterozygous TOR1A mutation show reduced neurite length and branches, markedly thickened nuclear lamina, disrupted nuclear morphology, and impaired nucleocytoplasmic transport (NCT) of mRNAs and proteins, whereas they lack the perinuclear "blebs" that are often observed in animal models. Furthermore, we uncover that the nuclear lamina protein LMNB1 is upregulated in DYT1 cells and exhibits abnormal subcellular distribution in a cholinergic MNs-specific manner. Such dysregulation of LMNB1 can be recapitulated by either ectopic expression of the mutant TOR1A gene or shRNA-mediated downregulation of endogenous TOR1A in healthy control MNs. Interestingly, downregulation of LMNB1 can largely ameliorate all the cellular defects in DYT1 MNs. These results reveal the value of disease modeling with human patient-specific neurons and indicate that dysregulation of LMNB1, a crucial component of the nuclear lamina, may constitute a major molecular mechanism underlying DYT1 pathology.SIGNIFICANCE STATEMENT Inaccessibility to patient neurons greatly impedes our understanding of the pathologic mechanisms for dystonia. In this study, we employ reprogrammed human patient-specific motor neurons (MNs) to model DYT1, the most severe hereditary form of dystonia. Our results reveal disease-dependent deficits in nuclear morphology and nucleocytoplasmic transport (NCT). Most importantly, we further identify LMNB1 dysregulation as a major contributor to these deficits, uncovering a new pathologic mechanism for DYT1 dystonia.
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Affiliation(s)
- Baojin Ding
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Biology, University of Louisiana at Lafayette, Lafayette, Louisiana 70503
| | - Yu Tang
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- National Clinical Research Center for Geriatric Disorders, Department of Geriatrics, Xiangya Hospital, Central South University, Changsha, Hunan Province 410008, China
| | - Shuaipeng Ma
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Masuma Akter
- Department of Biology, University of Louisiana at Lafayette, Lafayette, Louisiana 70503
| | - Meng-Lu Liu
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Tong Zang
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Chun-Li Zhang
- Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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Abstract
The human immunodeficiency virus type 1 (HIV-1) proteome is expressed from alternatively spliced and unspliced genomic RNAs. However, HIV-1 RNAs that are not fully spliced are perceived by the host machinery as defective and are retained in the nucleus. During late infection, HIV-1 bypasses this regulatory mechanism by expression of the Rev protein from a fully spliced mRNA. Once imported into the nucleus, Rev mediates the export of unprocessed HIV-1 RNAs to the cytoplasm, leading to the production of the viral progeny. While regarded as a canonical RNA export factor, Rev has also been linked to HIV-1 RNA translation, stabilization, splicing and packaging. However, Rev's functions beyond RNA export have remained poorly understood. Here, we revisit this paradigmatic protein, reviewing recent data investigating its structure and function. We conclude by asking: what remains unknown about this enigmatic viral protein?
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Affiliation(s)
| | - Aino Järvelin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Alfredo Castello
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
- MRC-University of Glasgow Centre for Virus Research, University of Glasgow, 464 Bearsden Road, Glasgow G61 1QH, UK
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32
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Bell PJ. Evidence supporting a viral origin of the eukaryotic nucleus. Virus Res 2020; 289:198168. [DOI: 10.1016/j.virusres.2020.198168] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 12/22/2022]
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33
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Chen ZH, Chen TQ, Zeng ZC, Wang D, Han C, Sun YM, Huang W, Sun LY, Fang K, Chen YQ, Luo XQ, Wang WT. Nuclear export of chimeric mRNAs depends on an lncRNA-triggered autoregulatory loop in blood malignancies. Cell Death Dis 2020; 11:566. [PMID: 32703936 PMCID: PMC7378249 DOI: 10.1038/s41419-020-02795-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 07/05/2020] [Accepted: 07/09/2020] [Indexed: 12/16/2022]
Abstract
Aberrant chromosomal translocations leading to tumorigenesis have been ascribed to the heterogeneously oncogenic functions. However, how fusion transcripts exporting remains to be declared. Here, we showed that the nuclear speckle-specific long noncoding RNA MALAT1 controls chimeric mRNA export processes and regulates myeloid progenitor cell differentiation in malignant hematopoiesis. We demonstrated that MALAT1 regulates chimeric mRNAs export in an m6A-dependent manner and thus controls hematopoietic cell differentiation. Specifically, reducing MALAT1 or m6A methyltransferases and the 'reader' YTHDC1 result in the universal retention of distinct oncogenic gene mRNAs in nucleus. Mechanically, MALAT1 hijacks both the chimeric mRNAs and fusion proteins in nuclear speckles during chromosomal translocations and mediates the colocalization of oncogenic fusion proteins with METTL14. MALAT1 and fusion protein complexes serve as a functional loading bridge for the interaction of chimeric mRNA and METTL14. This study demonstrated a universal mechanism of chimeric mRNA transport that involves lncRNA-fusion protein-m6A autoregulatory loop for controlling myeloid cell differentiation. Targeting the lncRNA-triggered autoregulatory loop to disrupt chimeric mRNA transport might represent a new common paradigm for treating blood malignancies.
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Affiliation(s)
- Zhen-Hua Chen
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Tian-Qi Chen
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Zhan-Cheng Zeng
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Dan Wang
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, 510060, Guangzhou, Guangdong, China
| | - Cai Han
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Yu-Meng Sun
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Wei Huang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Lin-Yu Sun
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Ke Fang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Yue-Qin Chen
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China
| | - Xue-Qun Luo
- The First Affiliated Hospital, Sun Yat-sen University, 510080, Guangzhou, China
| | - Wen-Tao Wang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, 510275, Guangzhou, China.
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Fazal FM, Chang HY. Subcellular Spatial Transcriptomes: Emerging Frontier for Understanding Gene Regulation. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2020; 84:31-45. [PMID: 32482897 PMCID: PMC7426137 DOI: 10.1101/sqb.2019.84.040352] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
RNAs are trafficked and localized with exquisite precision inside the cell. Studies of candidate messenger RNAs have shown the vital importance of RNA subcellular location in development and cellular function. New sequencing- and imaging-based methods are providing complementary insights into subcellular localization of RNAs transcriptome-wide. APEX-seq and ribosome profiling as well as proximity-labeling approaches have revealed thousands of transcript isoforms are localized to distinct cytotopic locations, including locations that defy biochemical fractionation and hence were missed by prior studies. Sequences in the 3' and 5' untranslated regions (UTRs) serve as "zip codes" to direct transcripts to particular locales, and it is clear that intronic and retrotransposable sequences within transcripts have been co-opted by cells to control localization. Molecular motors, nuclear-to-cytosol RNA export, liquid-liquid phase separation, RNA modifications, and RNA structure dynamically shape the subcellular transcriptome. Location-based RNA regulation continues to pose new mysteries for the field, yet promises to reveal insights into fundamental cell biology and disease mechanisms.
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Affiliation(s)
- Furqan M Fazal
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, California 94305, USA
| | - Howard Y Chang
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, California 94305, USA
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA
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Christou-Kent M, Dhellemmes M, Lambert E, Ray PF, Arnoult C. Diversity of RNA-Binding Proteins Modulating Post-Transcriptional Regulation of Protein Expression in the Maturing Mammalian Oocyte. Cells 2020; 9:cells9030662. [PMID: 32182827 PMCID: PMC7140715 DOI: 10.3390/cells9030662] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 03/02/2020] [Accepted: 03/03/2020] [Indexed: 12/18/2022] Open
Abstract
The oocyte faces a particular challenge in terms of gene regulation. When oocytes resume meiosis at the end of the growth phase and prior to ovulation, the condensed chromatin state prevents the transcription of genes as they are required. Transcription is effectively silenced from the late germinal vesicle (GV) stage until embryonic genome activation (EGA) following fertilisation. Therefore, during its growth, the oocyte must produce the mRNA transcripts needed to fulfil its protein requirements during the active period of meiotic completion, fertilisation, and the maternal-to zygote-transition (MZT). After meiotic resumption, gene expression control can be said to be transferred from the nucleus to the cytoplasm, from transcriptional regulation to translational regulation. Maternal RNA-binding proteins (RBPs) are the mediators of translational regulation and their role in oocyte maturation and early embryo development is vital. Understanding these mechanisms will provide invaluable insight into the oocyte's requirements for developmental competence, with important implications for the diagnosis and treatment of certain types of infertility. Here, we give an overview of post-transcriptional regulation in the oocyte, emphasising the current knowledge of mammalian RBP mechanisms, and develop the roles of these mechanisms in the timely activation and elimination of maternal transcripts.
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Affiliation(s)
- Marie Christou-Kent
- Université Grenoble Alpes, F-38000 Grenoble, France; (M.C.-K.); (M.D.); (E.L.); (P.F.R.)
- Institute for Advanced Biosciences INSERM U1209, CNRS UMR5309, F-38000 Grenoble, France
| | - Magali Dhellemmes
- Université Grenoble Alpes, F-38000 Grenoble, France; (M.C.-K.); (M.D.); (E.L.); (P.F.R.)
- Institute for Advanced Biosciences INSERM U1209, CNRS UMR5309, F-38000 Grenoble, France
| | - Emeline Lambert
- Université Grenoble Alpes, F-38000 Grenoble, France; (M.C.-K.); (M.D.); (E.L.); (P.F.R.)
- Institute for Advanced Biosciences INSERM U1209, CNRS UMR5309, F-38000 Grenoble, France
| | - Pierre F. Ray
- Université Grenoble Alpes, F-38000 Grenoble, France; (M.C.-K.); (M.D.); (E.L.); (P.F.R.)
- Institute for Advanced Biosciences INSERM U1209, CNRS UMR5309, F-38000 Grenoble, France
- CHU de Grenoble, UM GI-DPI, F-38000 Grenoble, France
| | - Christophe Arnoult
- Université Grenoble Alpes, F-38000 Grenoble, France; (M.C.-K.); (M.D.); (E.L.); (P.F.R.)
- Institute for Advanced Biosciences INSERM U1209, CNRS UMR5309, F-38000 Grenoble, France
- Correspondence: ; Tel.: +33-(0)4-76-63-74-08
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36
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Niikura M, Fukutomi T, Fukui K, Inoue SI, Asahi H, Kobayashi F. G-strand binding protein 2 is involved in asexual and sexual development of Plasmodium berghei. Parasitol Int 2020; 76:102059. [PMID: 31958569 DOI: 10.1016/j.parint.2020.102059] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 01/06/2020] [Accepted: 01/14/2020] [Indexed: 02/06/2023]
Abstract
G-strand binding protein 2 (GBP2) is a Ser/Arg-rich (SR) protein involved in mRNA surveillance and nuclear mRNA quality control in yeast. However, the roles of GBP2 in virulence and sexual development in Plasmodium parasites are unclear, although GBP2 is involved in the asexual development of Plasmodium berghei, the rodent malaria parasite. In this study, we investigated the role of GBP2 in virulence and sexual development of P. berghei using gbp2-deleted P. berghei (Δgbp2 parasites). Then, to identify factors affected by gbp2 deletion, we performed a comparative proteomic analysis of the Δgbp2 parasites. We found that GBP2 was not associated with the development of experimental cerebral malaria during infection with P. berghei, but asexual development of the parasite was delayed with deletion of gbp2. However, the development of P. berghei gametocytes was significantly reduced with deletion of gbp2. Comparative proteomic analysis revealed that the levels of adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and hypoxanthine-guanine phosphoribosyltransferase (HGPRT) in Δgbp2 parasites were significantly higher than those in wild-type (WT) parasites, suggesting that biosynthesis of purine nucleotides may be involved in function of GBP2. Therefore, we investigated the effect of purine starvation on the sexual development and proteome. In nt1-deleted P. berghei (Δnt1 parasites), the production of male and female gametocytes was significantly reduced compared to that in WT parasites. Moreover, we found that protein levels of GBP2 in Δnt1 parasites were markedly lower than in WT parasites. These findings suggest that GBP2 is primarily involved in the sexual development of malaria parasites, and its function may be suppressed by purine starvation.
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Affiliation(s)
- Mamoru Niikura
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan.
| | - Toshiyuki Fukutomi
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
| | - Kana Fukui
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan
| | - Shin-Ichi Inoue
- Division of Immunology, Department of Molecular Microbiology and Immunology, Nagasaki University, Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Hiroko Asahi
- Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan
| | - Fumie Kobayashi
- Department of Environmental Science, School of Life and Environmental Science, Azabu University, Japan
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37
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Larsen MC, Lee J, Jorgensen JS, Jefcoate CR. STARD1 Functions in Mitochondrial Cholesterol Metabolism and Nascent HDL Formation. Gene Expression and Molecular mRNA Imaging Show Novel Splicing and a 1:1 Mitochondrial Association. Front Endocrinol (Lausanne) 2020; 11:559674. [PMID: 33193082 PMCID: PMC7607000 DOI: 10.3389/fendo.2020.559674] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 09/22/2020] [Indexed: 12/13/2022] Open
Abstract
STARD1 moves cholesterol (CHOL) from the outer mitochondrial membrane (OMM) to the inner membrane (IMM) in steroidogenic cells. This activity is integrated into CHOL trafficking and synthesis homeostasis, involving uptake through SR-B1 and LDL receptors and distribution through endosomes, ER, and lipid droplets. In adrenal cells, STARD1 is imported into the mitochondrial matrix accompanied by delivery of several hundred CHOL molecules. This transfer limits CYP11A1-mediated generation of pregnenolone. CHOL transfer is coupled to translation of STARD1 mRNA at the OMM. In testis cells, slower CHOL trafficking seems to be limiting. STARD1 also functions in a slower process through ER OMM contacts. The START domain of STARD1 is utilized by a family of genes, which includes additional STARD (forms 3-6) and GRAMD1B proteins that transfer CHOL. STARD forms 2 and 7 deliver phosphatidylcholine. STARD1 and STARD7 target their respective activities to mitochondria, via N-terminal domains (NTD) of over 50 amino acids. The NTD is not essential for steroidogenesis but exerts tissue-selective enhancement (testis>>adrenal). Three conserved sites for cleavage by the mitochondrial processing protease (MPP) generate three forms, each potentially with specific functions, as demonstrated in STARD7. STARD1 is expressed in macrophage and cardiac repair fibroblasts. Additional functions include CHOL metabolism by CYP27A1 that directs activation of LXR and CHOL export processes. STARD1 generates 3.5- and 1.6-kb mRNA from alternative polyadenylation. The 3.5-kb form exclusively binds the PKA-induced regulator, TIS11b, which binds at conserved sites in the extended 3'UTR to control mRNA translation and turnover. STARD1 expression also exhibits a novel, slow splicing that delayed splicing delivery of mRNA to mitochondria. Stimulation of transcription by PKA is directed by suppression of SIK forms that activate a CRTC/CREB/CBP promoter complex. This process is critical to pulsatile hormonal activation in vivo. sm-FISH RNA imaging shows a flow of single STARD1 mRNA particles from asymmetric accumulations of primary transcripts at gene loci to 1:1 complex of 3.5-kb mRNA with peri-nuclear mitochondria. Adrenal cells are similar but distinguished from testis cells by appreciable basal expression prior to hormonal activation. This difference is conserved in culture and in vivo.
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Affiliation(s)
- Michele Campaigne Larsen
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Jinwoo Lee
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
- Endocrinology and Reproductive Physiology Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Joan S. Jorgensen
- Endocrinology and Reproductive Physiology Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
- Department of Comparative Biosciences, University of Wisconsin School of Veterinary Medicine, Madison, WI, United States
| | - Colin R. Jefcoate
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
- Endocrinology and Reproductive Physiology Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
- *Correspondence: Colin R. Jefcoate,
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38
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Zhao K, Cheng S, Miao N, Xu P, Lu X, Zhang Y, Wang M, Ouyang X, Yuan X, Liu W, Lu X, Zhou P, Gu J, Zhang Y, Qiu D, Jin Z, Su C, Peng C, Wang JH, Dong MQ, Wan Y, Ma J, Cheng H, Huang Y, Yu Y. A Pandas complex adapted for piRNA-guided transcriptional silencing and heterochromatin formation. Nat Cell Biol 2019; 21:1261-1272. [PMID: 31570835 DOI: 10.1038/s41556-019-0396-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/22/2019] [Indexed: 11/09/2022]
Abstract
The repression of transposons by the Piwi-interacting RNA (piRNA) pathway is essential to protect animal germ cells. In Drosophila, Panoramix enforces transcriptional silencing by binding to the target-engaged Piwi-piRNA complex, although the precise mechanisms by which this occurs remain elusive. Here, we show that Panoramix functions together with a germline-specific paralogue of a nuclear export factor, dNxf2, and its cofactor dNxt1 (p15), to suppress transposon expression. The transposon RNA-binding protein dNxf2 is required for animal fertility and Panoramix-mediated silencing. Transient tethering of dNxf2 to nascent transcripts leads to their nuclear retention. The NTF2 domain of dNxf2 competes dNxf1 (TAP) off nucleoporins, a process required for proper RNA export. Thus, dNxf2 functions in a Panoramix-dNxf2-dependent TAP/p15 silencing (Pandas) complex that counteracts the canonical RNA exporting machinery and restricts transposons to the nuclear peripheries. Our findings may have broader implications for understanding how RNA metabolism modulates heterochromatin formation.
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Affiliation(s)
- Kang Zhao
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Sha Cheng
- University of Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Na Miao
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ping Xu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,National Engineering Laboratory of AIDS Vaccine, Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun, China
| | - Xiaohua Lu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yuhan Zhang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.,State Key Laboratory of Genetic Engineering, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai, China
| | - Ming Wang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xuan Ouyang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xun Yuan
- University of Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Weiwei Liu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xin Lu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Peng Zhou
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Jiaqi Gu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Genetic Engineering, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai, China
| | - Yiqun Zhang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Ding Qiu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Zhaohui Jin
- University of Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Chen Su
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai, China
| | - Chao Peng
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai, China
| | - Jian-Hua Wang
- Graduate School of Peking Union Medical College and Chinese Academy of Sciences of Medical Sciences, Beijing, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences, Beijing, China.,Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China
| | - Youzhong Wan
- National Engineering Laboratory of AIDS Vaccine, Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun, China
| | - Jinbiao Ma
- State Key Laboratory of Genetic Engineering, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai, China
| | - Hong Cheng
- University of Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Ying Huang
- University of Chinese Academy of Sciences, Beijing, China. .,State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China. .,Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai Research Center of Biliary Tract Disease, Department of General Surgery, Xinhua Hospital, affiliated with Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Yang Yu
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China. .,University of Chinese Academy of Sciences, Beijing, China.
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39
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Reduction of mRNA export unmasks different tissue sensitivities to low mRNA levels during Caenorhabditis elegans development. PLoS Genet 2019; 15:e1008338. [PMID: 31525188 PMCID: PMC6762213 DOI: 10.1371/journal.pgen.1008338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 09/26/2019] [Accepted: 07/31/2019] [Indexed: 12/25/2022] Open
Abstract
Animal development requires the execution of specific transcriptional programs in different sets of cells to build tissues and functional organs. Transcripts are exported from the nucleus to the cytoplasm where they are translated into proteins that, ultimately, carry out the cellular functions. Here we show that in Caenorhabditis elegans, reduction of mRNA export strongly affects epithelial morphogenesis and germline proliferation while other tissues remain relatively unaffected. Epithelialization and gamete formation demand a large number of transcripts in the cytoplasm for the duration of these processes. In addition, our findings highlight the existence of a regulatory feedback mechanism that activates gene expression in response to low levels of cytoplasmic mRNA. We expand the genetic characterization of nuclear export factor NXF-1 to other members of the mRNA export pathway to model mRNA export and recycling of NXF-1 back to the nucleus. Our model explains how mutations in genes involved in general processes, such as mRNA export, may result in tissue-specific developmental phenotypes. The Central Dogma of Biology schematically highlights the transmission of genetic information stored in DNA, through RNA, to the formation of proteins. This general flow implicates RNA export from the nucleus to the cytoplasm and proper protein localization within the eukaryotic cell. Ultimately, proteins are the cell’s structural and catalytic functional units. As a result, cells differentiate into one cell type or another (such as epithelial, muscle, neuron…) and exhibit specific shape and functionality. Here we describe, in a C. elegans model, how mutations in genes involved in a general and ubiquitous mechanism, such as mRNA export, may result in tissue-specific developmental phenotypes that show up in processes that are highly demanding of cytoplasmic transcripts like epithelialization and gamete formation. A deep understanding of the mechanisms underlying the "connectors" shown in the Central Dogma of Biology is key both to unravel the general genetic control of an organism’s development and, at the same time, contribute to a better understanding of tissue-specific diseases.
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40
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Minocha R, Popova V, Kopytova D, Misiak D, Hüttelmaier S, Georgieva S, Sträßer K. Mud2 functions in transcription by recruiting the Prp19 and TREX complexes to transcribed genes. Nucleic Acids Res 2019; 46:9749-9763. [PMID: 30053068 PMCID: PMC6182176 DOI: 10.1093/nar/gky640] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 07/20/2018] [Indexed: 01/31/2023] Open
Abstract
The different steps of gene expression are intimately linked to coordinate and regulate this complex process. During transcription, numerous RNA-binding proteins are already loaded onto the nascent mRNA and package the mRNA into a messenger ribonucleoprotein particle (mRNP). These RNA-binding proteins are often also involved in other steps of gene expression than mRNA packaging. For example, TREX functions in transcription, mRNP packaging and nuclear mRNA export. Previously, we showed that the Prp19 splicing complex (Prp19C) is needed for efficient transcription as well as TREX occupancy at transcribed genes. Here, we show that the splicing factor Mud2 interacts with Prp19C and is needed for Prp19C occupancy at transcribed genes in Saccharomyces cerevisiae. Interestingly, Mud2 is not only recruited to intron-containing but also to intronless genes indicating a role in transcription. Indeed, we show for the first time that Mud2 functions in transcription. Furthermore, these functions of Mud2 are likely evolutionarily conserved as Mud2 is also recruited to an intronless gene and interacts with Prp19C in Drosophila melanogaster. Taken together, we classify Mud2 as a novel transcription factor that is necessary for the recruitment of mRNA-binding proteins to the transcription machinery. Thus, Mud2 is a multifunctional protein important for transcription, splicing and most likely also mRNP packaging.
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Affiliation(s)
- Rashmi Minocha
- Institute of Biochemistry, Justus Liebig University, Giessen 35392, Germany
| | - Varvara Popova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Daria Kopytova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Danny Misiak
- Institute of Molecular Medicine, Martin-Luther-University Halle Wittenberg, Halle 06120, Germany
| | - Stefan Hüttelmaier
- Institute of Molecular Medicine, Martin-Luther-University Halle Wittenberg, Halle 06120, Germany
| | - Sofia Georgieva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia
| | - Katja Sträßer
- Institute of Biochemistry, Justus Liebig University, Giessen 35392, Germany
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41
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Vasilyev N, Gao A, Serganov A. Noncanonical features and modifications on the 5'-end of bacterial sRNAs and mRNAs. WILEY INTERDISCIPLINARY REVIEWS. RNA 2019; 10:e1509. [PMID: 30276982 PMCID: PMC6657780 DOI: 10.1002/wrna.1509] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 09/05/2018] [Accepted: 09/17/2018] [Indexed: 12/20/2022]
Abstract
Although many eukaryotic transcripts contain cap structures, it has been long thought that bacterial RNAs do not carry any special modifications on their 5'-ends. In bacteria, primary transcripts are produced by transcription initiated with a nucleoside triphosphate and are therefore triphosphorylated on 5'-ends. Some transcripts are then processed by nucleases that yield monophosphorylated RNAs for specific cellular activities. Many primary transcripts are also converted to monophosphorylated species by removal of the terminal pyrophosphate for 5'-end-dependent degradation. Recent studies surprisingly revealed an expanded repertoire of chemical groups on 5'-ends of bacterial RNAs. In addition to mono- and triphosphorylated moieties, some mRNAs and sRNAs contain cap-like structures and diphosphates on their 5'-ends. Although incorporation and removal of these groups have become better understood in recent years, the physiological significance of these modifications remain obscure. This review highlights recent studies aimed at identification and elucidation of novel modifications on the 5'-ends of bacterial RNAs and discusses possible physiological applications of the modified RNAs. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNA Structure and Dynamics > RNA Structure, Dynamics, and Chemistry RNA Processing > Capping and 5' End Modifications.
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Affiliation(s)
- Nikita Vasilyev
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Ang Gao
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA
| | - Alexander Serganov
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA
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42
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Abstract
In eukaryotes, the separation of translation from transcription by the nuclear envelope enables mRNA modifications such as capping, splicing, and polyadenylation. These modifications are mediated by a spectrum of ribonuclear proteins that associate with preRNA transcripts, coordinating the different steps and coupling them to nuclear export, ensuring that only mature transcripts reach the cytoplasmic translation machinery. Although the components of this machinery have been identified and considerable functional insight has been achieved, a number of questions remain outstanding about mRNA nuclear export and how it is integrated into the nuclear phase of the gene expression pathway. Nuclear export factors mediate mRNA transit through nuclear pores to the cytoplasm, after which these factors are removed from the mRNA, preventing transcripts from returning to the nucleus. However, as outlined in this review, several aspects of the mechanism by which transport factor binding and release are mediated remain unclear, as are the roles of accessory nuclear components in these processes. Moreover, the mechanisms by which completion of mRNA splicing and polyadenylation are recognized, together with how they are coordinated with nuclear export, also remain only partially characterized. One attractive hypothesis is that dissociating poly(A) polymerase from the cleavage and polyadenylation machinery could signal completion of mRNA maturation and thereby provide a mechanism for initiating nuclear export. The impressive array of genetic, molecular, cellular, and structural data that has been generated about these systems now provides many of the tools needed to define the precise mechanisms involved in these processes and how they are integrated.
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Affiliation(s)
- Murray Stewart
- From the MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, United Kingdom
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43
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Fasken MB, Corbett AH, Stewart M. Structure-function relationships in the Nab2 polyadenosine-RNA binding Zn finger protein family. Protein Sci 2019; 28:513-523. [PMID: 30578643 PMCID: PMC6371209 DOI: 10.1002/pro.3565] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 12/15/2018] [Accepted: 12/17/2018] [Indexed: 12/12/2022]
Abstract
The poly(A) RNA binding Zn finger ribonucleoprotein Nab2 functions to control the length of 3' poly(A) tails in Saccharomyces cerevisiae as well as contributing to the integration of the nuclear export of mature mRNA with preceding steps in the nuclear phase of the gene expression pathway. Nab2 is constructed from an N-terminal PWI-fold domain, followed by QQQP and RGG motifs and then seven CCCH Zn fingers. The nuclear pore-associated proteins Gfd1 and Mlp1 bind to opposite sides of the Nab2 N-terminal domain and function in the nuclear export of mRNA, whereas the Zn fingers, especially fingers 5-7, bind to A-rich regions of mature transcripts and function to regulate poly(A) tail length as well as mRNA compaction prior to nuclear export. Nab2 Zn fingers 5-7 have a defined spatial arrangement, with fingers 5 and 7 arranged on one side of the cluster and finger 6 on the other side. This spatial arrangement facilitates the dimerization of Nab2 when bound to adenine-rich RNAs and regulates both the termination of 3' polyadenylation and transcript compaction. Nab2 also functions to coordinate steps in the nuclear phase of the gene expression pathway, such as splicing and polyadenylation, with the generation of mature mRNA and its nuclear export. Nab2 orthologues in higher Eukaryotes have similar domain structures and play roles associated with the regulation of splicing and polyadenylation. Importantly, mutations in the gene encoding the human Nab2 orthologue ZC3H14 and cause intellectual disability.
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Affiliation(s)
- Milo B Fasken
- Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Anita H Corbett
- Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Murray Stewart
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, United Kingdom
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44
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Abstract
The Three prime repair exonuclease 2 (TREX-2) complex functions as a platform to which many of the components of the nuclear mRNA processing machinery bind, facilitating integration of this phase of the gene expression pathway, as well as mediating the re-positioning of highly regulated actively transcribing genes (such as GAL1) to nuclear pores (NPCs) to accelerate their activation. In Saccharomyces cerevisiae the TREX-2 complex is based on a Sac3 scaffold to which Thp1, Sem1, Cdc31 and two Sus1 chains are bound. A combination of X-ray crystallography and electron microscopy studies have established the structure of two major regions of this complex: the M-region that functions to bind nucleic acids and the CID region that functions to link the complex to nuclear pores. These structures have facilitated the engineering of mutants that have been used to define the contributions made by the TREX-2 complex to locating high-expressed genes to nuclear pores and the contributions made to mRNA nuclear export.
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Affiliation(s)
- Murray Stewart
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK.
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45
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Clark DP, Pazdernik NJ, McGehee MR. Processing of RNA. Mol Biol 2019. [DOI: 10.1016/b978-0-12-813288-3.00012-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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46
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Neueder A. RNA-Mediated Disease Mechanisms in Neurodegenerative Disorders. J Mol Biol 2018; 431:1780-1791. [PMID: 30597161 DOI: 10.1016/j.jmb.2018.12.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 12/14/2018] [Accepted: 12/16/2018] [Indexed: 12/16/2022]
Abstract
RNA is accurately entangled in virtually all pathways that maintain cellular homeostasis. To name but a few, RNA is the "messenger" between DNA encoded information and the resulting proteins. Furthermore, RNAs regulate diverse processes by forming DNA::RNA or RNA::RNA interactions. Finally, RNA itself can be the scaffold for ribonucleoprotein complexes, for example, ribosomes or cellular bodies. Consequently, disruption of any of these processes can lead to disease. This review describes known and emerging RNA-based disease mechanisms like interference with regular splicing, the anomalous appearance of RNA-protein complexes and uncommon RNA species, as well as non-canonical translation. Due to the complexity and entanglement of the above-mentioned pathways, only few drugs are available that target RNA-based disease mechanisms. However, advances in our understanding how RNA is involved in and modulates cellular homeostasis might pave the way to novel treatments.
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Affiliation(s)
- Andreas Neueder
- Experimental Neurology, Department of Neurology, Ulm University, 89081 Ulm, Germany.
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47
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Abstract
Although it was long assumed that eukaryotic pre-mRNAs are almost always spliced to generate linear mRNAs, it is now clear that thousands of protein-coding genes can be non-canonically spliced using backsplicing to produce circular RNAs (circRNAs). Most mature circRNAs accumulate in the cytoplasm; however, little is known about how circRNAs are exported from the nucleus to the cytoplasm as they lack many of the common signals used for mRNA export. In this point-of-view article, we will discuss our recently identified circRNA nuclear export pathway and address important open questions in the field.
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Affiliation(s)
- Zhengguo Li
- a School of Life Sciences , Chongqing University , Chongqing , China.,b Institute of Advanced Interdisciplinary Studies , Chongqing University , Chongqing , China
| | - Michael G Kearse
- c Department of Biochemistry and Biophysics , University of Pennsylvania, Perelman School of Medicine , Philadelphia , PA , USA
| | - Chuan Huang
- a School of Life Sciences , Chongqing University , Chongqing , China.,b Institute of Advanced Interdisciplinary Studies , Chongqing University , Chongqing , China
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48
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Sequences encoding C2H2 zinc fingers inhibit polyadenylation and mRNA export in human cells. Sci Rep 2018; 8:16995. [PMID: 30451889 PMCID: PMC6242934 DOI: 10.1038/s41598-018-35138-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 10/31/2018] [Indexed: 01/01/2023] Open
Abstract
The large C2H2-Zinc Finger (C2H2-ZNF) gene family has rapidly expanded in primates through gene duplication. There is consequently considerable sequence homology between family members at both the nucleotide and amino acid level, allowing for coordinated regulation and shared functions. Here we show that multiple C2H2-ZNF mRNAs experience differential polyadenylation resulting in populations with short and long poly(A) tails. Furthermore, a significant proportion of C2H2-ZNF mRNAs are retained in the nucleus. Intriguingly, both short poly(A) tails and nuclear retention can be specified by the repeated elements that encode zinc finger motifs. These Zinc finger Coding Regions (ZCRs) appear to restrict polyadenylation of nascent RNAs and at the same time impede their export. However, the polyadenylation process is not necessary for nuclear retention of ZNF mRNAs. We propose that inefficient polyadenylation and export may allow C2H2-ZNF mRNAs to moonlight as non-coding RNAs or to be stored for later use.
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49
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Li Y, Ke K, Spitale RC. Biochemical Methods To Image and Analyze RNA Localization: From One to Many. Biochemistry 2018; 58:379-386. [DOI: 10.1021/acs.biochem.8b01087] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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50
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Identification of the Novel Nup188-brr7 Allele in a Screen for Cold-Sensitive mRNA Export Mutants in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2018; 8:2991-3003. [PMID: 30021831 PMCID: PMC6118305 DOI: 10.1534/g3.118.200447] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The maturation and export of mRNA from the nucleus through the nuclear pore complex is critical for maintaining an appropriate proteome in all eukaryotic cells. Here we summarize a previously unpublished screen in S. cerevisiae that utilized an established dT50 in situ hybridization assay to identify cold-sensitive mutants that accumulated bulk poly A RNA in the nucleus. The screen identified seven mutants in six complementation groups, including the brr6-1 strain that we described previously. In addition to brr6-1, we identified novel alleles of the key transport gene GLE1 and NUP188, a component of the Nic96 nucleoporin complex. Notably, we show that the nup188-brr7 allele causes defects in select protein import pathways as well as mRNA export. Given recent structural and functional evidence linking the Nic96 complex to transport components, this mutant may be particularly useful to the transport community.
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