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Gorbea C, Elhakiem A, Cazalla D. Shaping the host cell environment with viral noncoding RNAs. Semin Cell Dev Biol 2023; 146:20-30. [PMID: 36581481 PMCID: PMC10101873 DOI: 10.1016/j.semcdb.2022.12.008] [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: 08/29/2022] [Revised: 12/24/2022] [Accepted: 12/24/2022] [Indexed: 12/29/2022]
Abstract
Just like the cells they infect viruses express different classes of noncoding RNAs (ncRNAs). Viral ncRNAs come in all shapes and forms, and they usually associate with cellular proteins that are important for their functions. Viral ncRNAs have diverse functions, but they all contribute to the viral control of the cellular environment. Viruses utilize ncRNAs to regulate viral replication, to decide whether they should remain latent or reactivate, to evade the host immune responses, or to promote cellular transformation. In this review we describe the diverse functions played by different classes of ncRNAs expressed by adenoviruses and herpesviruses, how they contribute to the viral infection, and how their study led to insights into RNA-based mechanisms at play in host cells.
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Affiliation(s)
- Carlos Gorbea
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Abdalla Elhakiem
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Demián Cazalla
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
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2
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Jesenko T, Brezar SK, Cemazar M, Biasin A, Tierno D, Scaggiante B, Grassi M, Grassi C, Dapas B, Truong NH, Abrami M, Zanconati F, Bonazza D, Rizzolio F, Parisi S, Pastorin G, Grassi G. Targeting Non-Coding RNAs for the Development of Novel Hepatocellular Carcinoma Therapeutic Approaches. Pharmaceutics 2023; 15:pharmaceutics15041249. [PMID: 37111734 PMCID: PMC10145575 DOI: 10.3390/pharmaceutics15041249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 04/12/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
Hepatocellular carcinoma (HCC) remains a global health challenge, representing the third leading cause of cancer deaths worldwide. Although therapeutic advances have been made in the few last years, the prognosis remains poor. Thus, there is a dire need to develop novel therapeutic strategies. In this regard, two approaches can be considered: (1) the identification of tumor-targeted delivery systems and (2) the targeting of molecule(s) whose aberrant expression is confined to tumor cells. In this work, we focused on the second approach. Among the different kinds of possible target molecules, we discuss the potential therapeutic value of targeting non-coding RNAs (ncRNAs), which include micro interfering RNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). These molecules represent the most significant RNA transcripts in cells and can regulate many HCC features, including proliferation, apoptosis, invasion and metastasis. In the first part of the review, the main characteristics of HCC and ncRNAs are described. The involvement of ncRNAs in HCC is then presented over five sections: (a) miRNAs, (b) lncRNAs, (c) circRNAs, (d) ncRNAs and drug resistance and (e) ncRNAs and liver fibrosis. Overall, this work provides the reader with the most recent state-of-the-art approaches in this field, highlighting key trends and opportunities for more advanced and efficacious HCC treatments.
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Affiliation(s)
- Tanja Jesenko
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Zaloska 2, SI-1000 Ljubljana, Slovenia
| | - Simona Kranjc Brezar
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Zaloska 2, SI-1000 Ljubljana, Slovenia
| | - Maja Cemazar
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Zaloska 2, SI-1000 Ljubljana, Slovenia
- Faculty of Health Sciences, University of Primorska, Polje 42, SI-6310 Izola, Slovenia
| | - Alice Biasin
- Department of Engineering and Architecture, Trieste University, via Valerio 6, I-34127 Trieste, Italy
| | - Domenico Tierno
- Department of Life Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy
| | - Bruna Scaggiante
- Department of Life Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy
| | - Mario Grassi
- Department of Engineering and Architecture, Trieste University, via Valerio 6, I-34127 Trieste, Italy
| | - Chiara Grassi
- Degree Course in Medicine, University of Trieste, I-34149 Trieste, Italy
| | - Barbara Dapas
- Department of Life Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy
| | - Nhung Hai Truong
- Faculty of Biology and Biotechnology, VNUHCM-University of Science, Ho Chi Minh City 70000, Vietnam
| | - Michela Abrami
- Department of Engineering and Architecture, Trieste University, via Valerio 6, I-34127 Trieste, Italy
| | - Fabrizio Zanconati
- Department of Medical, Surgical and Health Sciences, University of Trieste, Cattinara Hospital, Strada di Fiume, 447, I-34149 Trieste, Italy
| | - Deborah Bonazza
- Department of Medical, Surgical and Health Sciences, University of Trieste, Cattinara Hospital, Strada di Fiume, 447, I-34149 Trieste, Italy
| | - Flavio Rizzolio
- Pathology Unit, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, I-33081 Aviano, Italy
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, I-30172 Venezia, Italy
| | - Salvatore Parisi
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, I-30172 Venezia, Italy
- Doctoral School in Molecular Biomedicine, University of Trieste, I-34149 Trieste, Italy
| | - Giorgia Pastorin
- Pharmacy Department, National University of Singapore, Block S9, Level 15, 4 Science Drive 2, Singapore 117544, Singapore
| | - Gabriele Grassi
- Department of Life Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy
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3
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Characterization of Viral miRNAs during Adenovirus 14 Infection and Their Differential Expression in the Emergent Strain Adenovirus 14p1. Viruses 2022; 14:v14050898. [PMID: 35632641 PMCID: PMC9145648 DOI: 10.3390/v14050898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 04/20/2022] [Accepted: 04/21/2022] [Indexed: 02/04/2023] Open
Abstract
Human adenoviruses (HAdV) express either one or two virus-associated RNAs (VA RNAI or VA RNAII). The structure of VA RNA resembles human precursor microRNAs (pre-miRNA), and, like human pre-miRNA, VA RNA can be processed by DICER into small RNAs that resemble human miRNA. VA RNA-derived miRNA (mivaRNA) can mimic human miRNA post-transcriptional gene repression by binding to complementary sequences in the 3′ UTR of host mRNA. HAdV14 is a member of the B2 subspecies of species B adenovirus, and the emergent strain HAdV14p1 is associated with severe respiratory illness that can lead to acute respiratory distress syndrome. Utilizing small RNA sequencing, we identified four main mivaRNAs generated from the HAdV14/p1 VA RNA gene, two from each of the 5′ and 3′ regions of the terminal stem. There were temporal expression changes in the abundance of 5′ and 3′ mivaRNAs, with 3′ mivaRNAs more highly expressed early in infection and 5′ mivaRNAs more highly expressed later in infection. In addition, there are differences in expression between the emergent and reference strains, with HAdV14 expressing more mivaRNAs early during infection and HAdV14p1 having higher expression later during infection. HAdV14/p1 mivaRNAs were also shown to repress gene expression in a luciferase gene reporter system. Our results raise the question as to whether differential expression of mivaRNAs during HAdV14p1 infection could play a role in the increased pathogenesis associated with the emergent strain.
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4
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Abstract
MicroRNAs (miRNAs) are short (~22 nucleotides) single-stranded RNA molecules that primarily function to negatively regulate gene expression at the post-transcriptional level. miRNAs have thus been implicated in the regulation of a wide variety of normal cell functions and pathophysiological conditions. The miRNA machinery consists of a series of protein complexes which act to: (1) cleave the precursor-miRNA hairpin from its primary transcript (i.e. DROSHA and DGCR8); (2) traffic the miRNA hairpin between nucleus and cytoplasm (i.e. XPO5); (3) remove the loop sequence of the hairpin by a second nucleolytic cleavage reaction (i.e. DICER1); (4) facilitate loading of the mature miRNA sequence into an Argonaute protein (typically AGO2) as part of the RNA-Induced Silencing Complex (RISC); (5) guide the loaded RISC complex to complementary, or semi-complementary, target transcripts and (6) facilitate gene silencing via one of several possible mechanisms.
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5
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Kowalski MP, Krude T. Functional roles of non-coding Y RNAs. Int J Biochem Cell Biol 2015; 66:20-9. [PMID: 26159929 PMCID: PMC4726728 DOI: 10.1016/j.biocel.2015.07.003] [Citation(s) in RCA: 146] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 07/03/2015] [Accepted: 07/04/2015] [Indexed: 12/20/2022]
Abstract
Non-coding RNAs are involved in a multitude of cellular processes but the biochemical function of many small non-coding RNAs remains unclear. The family of small non-coding Y RNAs is conserved in vertebrates and related RNAs are present in some prokaryotic species. Y RNAs are also homologous to the newly identified family of non-coding stem-bulge RNAs (sbRNAs) in nematodes, for which potential physiological functions are only now emerging. Y RNAs are essential for the initiation of chromosomal DNA replication in vertebrates and, when bound to the Ro60 protein, they are involved in RNA stability and cellular responses to stress in several eukaryotic and prokaryotic species. Additionally, short fragments of Y RNAs have recently been identified as abundant components in the blood and tissues of humans and other mammals, with potential diagnostic value. While the number of functional roles of Y RNAs is growing, it is becoming increasingly clear that the conserved structural domains of Y RNAs are essential for distinct cellular functions. Here, we review the biochemical functions associated with these structural RNA domains, as well as the functional conservation of Y RNAs in different species. The existing biochemical and structural evidence supports a domain model for these small non-coding RNAs that has direct implications for the modular evolution of functional non-coding RNAs.
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Affiliation(s)
- Madzia P Kowalski
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom
| | - Torsten Krude
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom.
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6
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Vachon VK, Conn GL. Adenovirus VA RNA: An essential pro-viral non-coding RNA. Virus Res 2015; 212:39-52. [PMID: 26116898 DOI: 10.1016/j.virusres.2015.06.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 06/15/2015] [Accepted: 06/17/2015] [Indexed: 12/25/2022]
Abstract
Adenovirus (AdV) 'virus-associated' RNAs (VA RNAs) are exceptionally abundant (up to 10(8)copies/cell), heterogeneous, non-coding RNA transcripts (∼ 150-200 nucleotides). The predominant species, VA RNAI, is best recognized for its essential function in relieving the cellular anti-viral blockade of protein synthesis through inhibition of the double-stranded RNA-activated protein kinase (PKR). More recent evidence has revealed that VA RNAs also interfere with several other host cell processes, in part by virtue of the high level to which they accumulate. Following transcription by cellular RNA polymerase III, VA RNAs saturate the nuclear export protein Exportin 5 (Exp5) and the cellular endoribonculease Dicer, interfering with pre-micro (mi)RNA export and miRNA biogenesis, respectively. Dicer-processed VA RNA fragments are incorporated into the RNA-induced silencing complex (RISC) as 'mivaRNAs', where they may specifically target cellular genes. VA RNAI also interacts with other innate immune proteins, including OAS1. While intact VA RNAI has the paradoxical effect of activating OAS1, a non-natural VA RNAI construct lacking the entire Terminal Stem has been reported to be a pseudoinhibitor of OAS1. Here, we show that a VA RNAI construct corresponding to an authentic product of Dicer processing similarly fails to activate OAS1 but also retains only a modest level of inhibitory activity against PKR in contrast to the non-natural deletion construct. These findings underscore the complexity of the arms race between virus and host, and highlight the need for further exploration of the impact of VA RNAI interactions with host defenses on the outcome of AdV infection beyond that of well-established PKR inhibition. Additional contributions of VA RNAI heterogeneity resulting from variations in transcription initiation and termination to each of these functions remain open questions that are discussed here.
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Affiliation(s)
- Virginia K Vachon
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA; Microbiology and Molecular Genetics (MMG) Program, Graduate Division of Biological and Biomedical Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Graeme L Conn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA.
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7
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Takeiwa T, Taniguchi I, Ohno M. Exportin-5 mediates nuclear export of SRP RNA in vertebrates. Genes Cells 2015; 20:281-91. [PMID: 25656399 PMCID: PMC4418401 DOI: 10.1111/gtc.12218] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 12/12/2014] [Indexed: 12/25/2022]
Abstract
The signal recognition particle is a ribonucleoprotein complex that is essential for the translocation of nascent proteins into the endoplasmic reticulum. It has been shown that the RNA component (SRP RNA) is exported from the nucleus by CRM1 in the budding yeast. However, how SRP RNA is exported in higher species has been elusive. Here, we show that SRP RNA does not use the CRM1 pathway in Xenopus oocytes. Instead, SRP RNA uses the same export pathway as pre-miRNA and tRNA as showed by cross-competition experiments. Consistently, the recombinant Exportin-5 protein specifically stimulated export of SRP RNA as well as of pre-miRNA and tRNA, whereas an antibody raised against Exportin-5 specifically inhibited export of the same RNA species. Moreover, biotinylated SRP RNA can pull down Exportin-5 but not CRM1 from HeLa cell nuclear extracts in a RanGTP-dependent manner. These results, taken together, strongly suggest that the principal export receptor for SRP RNA in vertebrates is Exportin-5 unlike in the budding yeast.
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Affiliation(s)
- Toshihiko Takeiwa
- Institute for Virus Research, Kyoto UniversityKyoto, 606-8507, Japan
| | - Ichiro Taniguchi
- Institute for Virus Research, Kyoto UniversityKyoto, 606-8507, Japan
| | - Mutsuhito Ohno
- Institute for Virus Research, Kyoto UniversityKyoto, 606-8507, Japan
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8
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Smith R, Rathod RJ, Rajkumar S, Kennedy D. Nervous translation, do you get the message? A review of mRNPs, mRNA-protein interactions and translational control within cells of the nervous system. Cell Mol Life Sci 2014; 71:3917-37. [PMID: 24952431 PMCID: PMC11113408 DOI: 10.1007/s00018-014-1660-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 05/22/2014] [Accepted: 05/30/2014] [Indexed: 01/01/2023]
Abstract
In neurons, translation of a message RNA can occur metres away from its transcriptional origin and in normal cells this is orchestrated with perfection. The life of an mRNA will see it pass through multiple steps of processing in the nucleus and the cytoplasm before it reaches its final destination. Processing of mRNA is determined by a myriad of RNA-binding proteins in multi-protein complexes called messenger ribonucleoproteins; however, incorrect processing and delivery of mRNA can cause several human neurological disorders. This review takes us through the life of mRNA from the nucleus to its point of translation in the cytoplasm. The review looks at the various cis and trans factors that act on the mRNA and discusses their roles in different cells of the nervous system and human disorders.
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Affiliation(s)
- Ross Smith
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia,
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9
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Burge RG, Martinez-Yamout MA, Dyson HJ, Wright PE. Structural characterization of interactions between the double-stranded RNA-binding zinc finger protein JAZ and nucleic acids. Biochemistry 2014; 53:1495-510. [PMID: 24521053 PMCID: PMC3985865 DOI: 10.1021/bi401675h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
![]()
The interactions of the human double-stranded
RNA-binding zinc
finger protein JAZ with RNA or DNA were investigated using electrophoretic
mobility-shift assays, isothermal calorimetry, and nuclear magnetic
resonance spectroscopy. Consistent with previous reports, JAZ has
very low affinity for duplex DNA or single-stranded RNA, but it binds
preferentially to double-stranded RNA (dsRNA) with no detectable sequence
specificity. The affinity of JAZ for dsRNA is unaffected by local
structural features such as loops, overhangs, and bulges, provided
a sufficient length of reasonably well-structured A-form RNA (about
18 bp for a single zinc finger) is present. Full-length JAZ contains
four Cys2His2 zinc fingers (ZF1–4) and
has the highest apparent affinity for dsRNA; two-finger constructs
ZF12 and ZF23 have lower affinity, and ZF34 binds even more weakly.
The fourth zinc finger, ZF4, has no measurable RNA-binding affinity.
Single zinc finger constructs ZF1, ZF2, and ZF3 show evidence for
multiple-site binding on the minimal RNA. Fitting of quantitative
NMR titration and isothermal calorimetry data to a two-site binding
model gave Kd1 ∼ 10 μM and Kd2 ∼ 100 μM. Models of JAZ–RNA
complexes were generated using the high-ambiguity-driven biomolecular
docking (HADDOCK) program. Single zinc fingers bind to the RNA backbone
without sequence specificity, forming complexes with contacts between
the RNA minor groove and residues in the N-terminal β strands
and between the major groove and residues in the helix–kink–helix
motif. We propose that the non-sequence-specific interaction between
the zinc fingers of JAZ with dsRNA is dependent only on the overall
shape of the A-form RNA.
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Affiliation(s)
- Russell G Burge
- Department of Integrative Structural and Computational Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute , La Jolla, California 92037, United States
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10
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Mingot JM, Vega S, Cano A, Portillo F, Nieto MA. eEF1A mediates the nuclear export of SNAG-containing proteins via the Exportin5-aminoacyl-tRNA complex. Cell Rep 2013; 5:727-37. [PMID: 24209753 DOI: 10.1016/j.celrep.2013.09.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/28/2013] [Accepted: 09/23/2013] [Indexed: 11/16/2022] Open
Abstract
Exportin5 mediates the nuclear export of double-stranded RNAs, including pre-microRNAs, adenoviral RNAs, and tRNAs. When tRNAs are aminoacylated, the Exportin5-aminoacyl (aa)-tRNA complex recruits and coexports the translation elongation factor eEF1A. Here, we show that eEF1A binds to Snail transcription factors when bound to their main target, the E-cadherin promoter, facilitating their export to the cytoplasm in association with the aa-tRNA-Exportin5 complex. Snail binds to eEF1A through the SNAG domain, a protein nuclear export signal present in several transcription factor families, and this binding is regulated by phosphorylation. Thus, we describe a nuclear role for eEF1A and provide a mechanism for protein nuclear export that attenuates the activity of SNAG-containing transcription factors.
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MESH Headings
- Active Transport, Cell Nucleus
- Amino Acid Sequence
- Cadherins/genetics
- Cadherins/metabolism
- Cell Nucleus/metabolism
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- HeLa Cells
- Humans
- Karyopherins/genetics
- Karyopherins/metabolism
- MCF-7 Cells
- Peptide Elongation Factor 1/genetics
- Peptide Elongation Factor 1/metabolism
- Promoter Regions, Genetic
- Protein Structure, Tertiary
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Snail Family Transcription Factors
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription, Genetic
- Transfection
- Exportin 1 Protein
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Affiliation(s)
- José Manuel Mingot
- Instituto de Neurociencias, CSIC-UMH, Avda. Ramón y Cajal s/n, 03550 San Juan de Alicante, Spain.
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11
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Abstract
MicroRNAs (miRNAs) function as 21-24 nucleotide guide RNAs that use partial base-pairing to recognize target messenger RNAs and repress their expression. As a large fraction of protein-coding genes are under miRNA control, production of the appropriate level of specific miRNAs at the right time and in the right place is integral to most gene regulatory pathways. MiRNA biogenesis initiates with transcription, followed by multiple processing steps to produce the mature miRNA. Every step of miRNA production is subject to regulation and disruption of these control mechanisms has been linked to numerous human diseases, where the balance between the expression of miRNAs and their targets becomes distorted. Here we review the basic steps of miRNA biogenesis and describe the various factors that control miRNA transcription, processing, and stability in animal cells. The tremendous effort put into producing the appropriate type and level of specific miRNAs underscores the critical role of these small RNAs in gene regulation.
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Affiliation(s)
- Emily F Finnegan
- Division of Biology, University of California, San Diego, La Jolla, CA 92093, USA
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12
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Bennasser Y, Chable-Bessia C, Triboulet R, Gibbings D, Gwizdek C, Dargemont C, Kremer EJ, Voinnet O, Benkirane M. Competition for XPO5 binding between Dicer mRNA, pre-miRNA and viral RNA regulates human Dicer levels. Nat Struct Mol Biol 2011; 18:323-7. [PMID: 21297638 DOI: 10.1038/nsmb.1987] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 11/23/2010] [Indexed: 12/31/2022]
Abstract
MicroRNAs (miRNAs) are a class of small, noncoding RNAs that function by regulating gene expression post-transcriptionally. Alterations in miRNA expression can strongly influence cellular physiology. Here we demonstrated cross-regulation between two components of the RNA interference (RNAi) machinery in human cells. Inhibition of exportin-5, the karyopherin responsible for pre-miRNA export, downregulated expression of Dicer, the RNase III required for pre-miRNA maturation. This effect was post-transcriptional and resulted from an increased nuclear localization of Dicer mRNA. In vitro assays and cellular RNA immunoprecipitation experiments showed that exportin-5 interacted directly with Dicer mRNA. Titration of exportin-5 by overexpression of either pre-miRNA or the adenoviral VA1 RNA resulted in loss of Dicer mRNA-exportin-5 interaction and reduction of Dicer level. This saturation also occurred during adenoviral infection and enhanced viral replication. Our study reveals an important cross-regulatory mechanism between pre-miRNA or viral small RNAs and Dicer through exportin-5.
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Affiliation(s)
- Yamina Bennasser
- Centre National de la Recherche Scientifique, Institut de Génétique Humaine UPR1142, Montpellier, France
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13
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Lee SJ, Jiko C, Yamashita E, Tsukihara T. Selective nuclear export mechanism of small RNAs. Curr Opin Struct Biol 2010; 21:101-8. [PMID: 21145229 DOI: 10.1016/j.sbi.2010.11.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 10/28/2010] [Accepted: 11/13/2010] [Indexed: 02/07/2023]
Abstract
The timely nuclear-cytoplasmic translocation of proteins and RNAs by importins and exportins is important for controlling biological processes. Since the 2004 publication of the first exportin structure, Cse1p, the X-ray structures of exportin-5 complexed with pre-microRNA, exportin-t complexed with tRNA, and three CRM1-related structures have revealed the binding mechanism involved in specific cargo recognition. Pre-microRNA and tRNA have conserved 3' 2-4-nucleotide overhang motifs and similar short double-stranded regions. Exportin-5 and exportin-t bind a conserved 3' overhang strongly, and they weakly enclose the short double-stranded stems, each in a different manner. The structures of the nuclear export complexes of small double-stranded RNAs, pre-microRNAs, and tRNAs provide information about the specificities of the two exportins in the context of transcription and translation control.
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Affiliation(s)
- Soo Jae Lee
- College of Pharmacy, Chungbuk National University, Heungduk-gu, Cheongju, Chungbuk, Republic of Korea.
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14
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Nayak R, Pintel DJ. Adeno-associated viruses can induce phosphorylation of eIF2alpha via PKR activation, which can be overcome by helper adenovirus type 5 virus-associated RNA. J Virol 2007; 81:11908-16. [PMID: 17715234 PMCID: PMC2168773 DOI: 10.1128/jvi.01132-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutants of adenovirus type 5 (Ad5) virus-associated RNA I deficient in inhibiting the activation and subsequent phosphorylation of protein kinase R (PKR) could neither function as helpers for adeno-associated virus type 5 (AAV5) replication nor enhance AAV5 protein accumulation in either the presence or absence of Ad5 E4Orf6 and E2a. Furthermore, a short region of the AAV5 capsid gene RNA leader sequence surrounding the AUG of VP1 could induce the phosphorylation of eIF2alpha. Both short interfering RNA directed against PKR and the addition of the herpes simplex virus ICP34.5 protein enhanced the accumulation of AAV5 capsid protein in the presence of the AAV5 capsid gene PKR-inducing element, suggesting that VA RNA acted to overcome direct AAV5-induced activation of PKR that led to the phosphorylation of eIF2alpha. The expression of both the closely related goat-derived AAV and the prototype AAV2 capsid gene transcription units also induced the phosphorylation of eIF2alpha, suggesting that the induction of the PKR/eIF2alpha cellular response may be a previously unrecognized general feature of at least the Dependovirus genus of the Parvovirinae.
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Affiliation(s)
- Ramnath Nayak
- Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri-Columbia, 1201 Rollins Road, Columbia, MO 65211, USA
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15
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Abstract
The discovery of RNA interference and cellular microRNAs (miRNAs) has not only affected how biological research is conducted but also revealed an entirely new level of post-transcriptional gene regulation. Here, I discuss the potential functions of the virally encoded miRNAs recently identified in several pathogenic human viruses and propose that cellular miRNAs may have had a substantial effect on viral evolution and may continue to influence the in vivo tissue tropism of viruses. Our increasing knowledge of the role and importance of virally encoded miRNAs will probably offer new insights into how viruses that establish latent infections, such as herpesviruses, avoid elimination by the host innate or adaptive immune system. Research into viral miRNA function might also suggest new approaches for treating some virally induced diseases.
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Affiliation(s)
- Bryan R Cullen
- Center for Virology and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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16
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Abstract
RNA interference constitutes a key component of the innate immune response to viral infection in both plants and invertebrate animals and has been postulated to have a similar protective function in mammals. This perspective reviews the available data addressing whether RNA interference forms part of the mammalian innate immune response and concludes that the popular hypothesis in favor of that possibility remains far from proven and may not be valid.
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Affiliation(s)
- Bryan R Cullen
- Center for Virology and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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17
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Fok V, Friend K, Steitz JA. Epstein-Barr virus noncoding RNAs are confined to the nucleus, whereas their partner, the human La protein, undergoes nucleocytoplasmic shuttling. J Cell Biol 2006; 173:319-25. [PMID: 16682524 PMCID: PMC2063832 DOI: 10.1083/jcb.200601026] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Accepted: 04/05/2006] [Indexed: 12/15/2022] Open
Abstract
The Epstein-Barr virus (EBV) noncoding RNAs, EBV-encoded RNA 1 (EBER1) and EBER2, are the most abundant viral transcripts in all types of latently infected human B cells, but their function remains unknown. We carried out heterokaryon assays using cells that endogenously produce EBERs to address their trafficking, as well as that of the La protein, because EBERs are quantitatively bound by La in vivo. Both in this assay and in oocyte microinjection assays, EBERs are confined to the nucleus, suggesting that their contribution to viral latency is purely nuclear. EBER1 does not bind exportin 5; therefore, it is unlikely to act by interfering with microRNA biogenesis. In contrast, La, which is a nuclear phosphoprotein, undergoes nucleocytoplasmic shuttling independent of the nuclear export protein Crm1. To ensure that small RNA shuttling can be detected in cells that are negative for EBER shuttling, we demonstrate the shuttling of U1 small nuclear RNA.
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Affiliation(s)
- Victor Fok
- Department of Molecular Biophysics and Biochemistry and 2Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06536, USA
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18
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Miki T, Takano K, Yoneda Y. The role of mammalian Staufen on mRNA traffic: a view from its nucleocytoplasmic shuttling function. Cell Struct Funct 2006; 30:51-6. [PMID: 16377940 DOI: 10.1247/csf.30.51] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The localization of mRNA in neuronal dendrites plays a role in both locally and temporally regulated protein synthesis, which is required for certain forms of synaptic plasticity. RNA granules constitute a dendritic mRNA transport machinery in neurons, which move along microtubules. RNA granules contain densely packed clusters of ribosomes, but lack some factors that are required for translation, suggesting that they are translationally incompetent. Recently some of the components of RNA granules have been identified, and their functions are in the process of being examined, in attempts to better understand the properties of RNA granules. Mammalian Staufen, a double-stranded RNA binding protein, is a component of RNA granules. Staufen is localized in the somatodendritic domain of neurons, and plays an important role in dendritic mRNA targeting. Recently, one of the mammalian homologs of Staufen, Staufen2 (Stau2), was shown to shuttle between the nucleus and the cytoplasm. This finding suggests the possibility that Stau2 binds RNA in the nucleus and that this ribonucleoprotein particle is transported from the nucleus to RNA granules in the cytoplasm. A closer study of this process might provide a clue to the mechanism by which RNA granules are formed.
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Affiliation(s)
- Takashi Miki
- Department of Cell Biology and Neuroscience, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan
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19
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Ohrt T, Merkle D, Birkenfeld K, Echeverri CJ, Schwille P. In situ fluorescence analysis demonstrates active siRNA exclusion from the nucleus by Exportin 5. Nucleic Acids Res 2006; 34:1369-80. [PMID: 16522647 PMCID: PMC1390680 DOI: 10.1093/nar/gkl001] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Two types of short double-stranded RNA molecules, namely microRNAs (miRNAs) and short interfering RNAs (siRNAs), have emerged recently as important regulators of gene expression. Although these molecules show similar sizes and structural features, the mechanisms of action underlying their respective target silencing activities appear to differ: siRNAs act primarily through mRNA degradation, whereas most miRNAs appear to act primarily through translational inhibition. Our understanding of how these overlapping pathways are differentially regulated within the cell remains incomplete. In the present work, quantitative fluorescence microscopy was used to study how siRNAs are processed within human cells. We found that siRNAs are excluded from non-nucleolar areas of the nucleus in an Exportin-5 dependent process that specifically recognizes key structural features shared by these and other small RNAs such as miRNAs. We further established that the Exportin-5-based exclusion of siRNAs from the nucleus can, when Exp5 itself is inhibited, become a rate-limiting step for siRNA-induced silencing activity. Exportin 5 therefore represents a key point of intersection between the siRNA and miRNA pathways, and, as such, is of fundamental importance for the design and interpretation of RNA interference experimentation.
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Affiliation(s)
| | | | | | | | - Petra Schwille
- To whom correspondence should be addressed. Tel: +49 351 463 40328; Fax: +49 351 463 40342;
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20
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Cullen BR. Transcription and processing of human microRNA precursors. Mol Cell 2005; 16:861-5. [PMID: 15610730 DOI: 10.1016/j.molcel.2004.12.002] [Citation(s) in RCA: 563] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Revised: 11/05/2004] [Accepted: 11/24/2004] [Indexed: 12/20/2022]
Abstract
MicroRNAs have recently emerged as key posttranscriptional regulators of eukaryotic gene expression, yet our understanding of how microRNA expression is itself controlled has remained rudimentary. This review describes recent insights into the mechanisms governing microRNA transcription and processing in vertebrates and their implications for understanding the regulation of microRNA biogenesis.
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Affiliation(s)
- Bryan R Cullen
- Howard Hughes Medical Institute and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
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21
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Abstract
The discovery of microRNSs (miRNAs) has changed the paradigm of gene regulation, leaving us with numerous exciting questions regarding what these molecules do and how they originate. A model for miRNA biogenesis has emerged recently, yet several key factors--including the identity of the miRNA nuclear export receptor--remained unknown. However, recent studies have shown that exportin-5 (Exp5), a Ran-dependent importin-beta-related transport receptor, mediates nuclear export of miRNA precursors (pre-miRNAs).
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Affiliation(s)
- V Narry Kim
- School of Biological Sciences and Institute of Molecular Biology and Genetics, Seoul National University, Korea.
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22
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Zeng Y, Cullen BR. Structural requirements for pre-microRNA binding and nuclear export by Exportin 5. Nucleic Acids Res 2004; 32:4776-85. [PMID: 15356295 PMCID: PMC519115 DOI: 10.1093/nar/gkh824] [Citation(s) in RCA: 315] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The biogenesis and function of mature human microRNAs is dependent on the nuclear export of pre-microRNA precursors by Exportin 5 (Exp5). The precursor for the human miR-30 microRNA, which is a 63 nt long RNA hairpin bearing a 2 nt 3' overhang, forms a specific complex with Exp5 and the Ran-GTP cofactor. Here, we have examined the structural requirements for pre-microRNA binding by Exp5. Our data indicate that pre-miR-30 binding requires an RNA stem of >16 bp and is facilitated by a 3' overhang. Although a blunt-ended derivative of the pre-miR-30 stem-loop remained capable of binding Exp5, 5' overhangs were inhibitory. miR-30 variants that had lost the ability to bind Exp5 effectively were not efficiently exported from the nucleus and were also expressed at reduced levels. Furthermore, formation of a pre-microRNA/Exp5/Ran-GTP complex inhibited exonucleolytic digestion of the pre-miRNA in vitro. Together, these data demonstrate that pre-microRNA binding by Exp5 involves recognition of almost all of the RNA hairpin, with the exception of the terminal loop. Moreover, these results argue that Exp5 binding not only mediates pre-microRNA nuclear export but also prevents nuclear pre-microRNA degradation.
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Affiliation(s)
- Yan Zeng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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23
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Chen T, Brownawell AM, Macara IG. Nucleocytoplasmic shuttling of JAZ, a new cargo protein for exportin-5. Mol Cell Biol 2004; 24:6608-19. [PMID: 15254228 PMCID: PMC444848 DOI: 10.1128/mcb.24.15.6608-6619.2004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 03/24/2004] [Accepted: 05/06/2004] [Indexed: 11/20/2022] Open
Abstract
Exportin-5 is a nuclear export receptor for certain classes of double-stranded RNA (dsRNA), including pre-micro-RNAs, viral hairpin RNAs, and some tRNAs. It can also export the RNA binding proteins ILF3 and elongation factor EF1A. However, the rules that determine which RNA binding proteins are exportin-5 cargoes remain unclear. JAZ possesses an unusual dsRNA binding domain consisting of multiple C2H2 zinc fingers. We found that JAZ binds to exportin-5 in a Ran-GTP- and dsRNA-dependent manner. Exportin-5 stimulates JAZ shuttling, and gene silencing of exportin-5 reduces shuttling. Recombinant exportin-5 also stimulates nuclear export of JAZ in permeabilized cells. JAZ also binds to ILF3, and surprisingly, this interaction is RNA independent, even though it requires the dsRNA binding domains of ILF3. Exportin-5, JAZ, and ILF3 can form a heteromeric complex with Ran-GTP and dsRNA, and JAZ increases ILF3 binding to exportin-5. JAZ does not contain a classical nuclear localization signal, and in digitonin-permeabilized cells, nuclear accumulation of JAZ does not require energy or cytosol. Nonetheless, low temperatures prevent JAZ import, suggesting that nuclear entry does not occur via simple diffusion. Together, these data suggest that JAZ is exported by exportin-5 but translocates back into nuclei by a facilitated diffusion mechanism.
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Affiliation(s)
- Ting Chen
- Center for Cell Signaling, Department of Microbiology, Health Sciences Center, University of Virginia School of Medicine, Charlottesville, VA 22908-0577, USA
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24
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Basyuk E, Suavet F, Doglio A, Bordonné R, Bertrand E. Human let-7 stem-loop precursors harbor features of RNase III cleavage products. Nucleic Acids Res 2004; 31:6593-7. [PMID: 14602919 PMCID: PMC275551 DOI: 10.1093/nar/gkg855] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The bidentate RNase III Dicer cleaves microRNA precursors to generate the 21-23 nt long mature RNAs. These precursors are 60-80 nt long, they fold into a characteristic stem-loop structure and they are generated by an unknown mechanism. To gain insights into the biogenesis of microRNAs, we have characterized the precise 5' and 3' ends of the let-7 precursors in human cells. We show that they harbor a 5'-phosphate and a 3'-OH and that, remarkably, they contain a 1-4 nt 3' overhang. These features are characteristic of RNase III cleavage products. Since these precursors are present in both the nucleus and the cytoplasm of human cells, our results suggest that they are generated in the nucleus by the nuclear RNase III. Additionally, these precursors fit the minihelix export motif and are thus likely exported by this pathway.
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Affiliation(s)
- Eugenia Basyuk
- IGMM-CNRS UMR 5535, IFR 24, 1919 Route de Mende, F-34293 Montpellier Cedex, France
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25
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Bohnsack MT, Czaplinski K, Gorlich D. Exportin 5 is a RanGTP-dependent dsRNA-binding protein that mediates nuclear export of pre-miRNAs. RNA (NEW YORK, N.Y.) 2004; 10:185-91. [PMID: 14730017 PMCID: PMC1370530 DOI: 10.1261/rna.5167604] [Citation(s) in RCA: 959] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
microRNAs (miRNAs) are widespread among eukaryotes, and studies in several systems have revealed that miRNAs can regulate expression of specific genes. Primary miRNA transcripts are initially processed to approximately 70-nucleotide (nt) stem-loop structures (pre-miRNAs), exported to the cytoplasm, further processed to yield approximately 22-nt dsRNAs, and finally incorporated into ribonucleoprotein particles, which are thought to be the active species. Here we study nuclear export of pre-miRNAs and show that the process is saturable and thus carrier-mediated. Export is sensitive to depletion of nuclear RanGTP and, according to this criterion, mediated by a RanGTP-dependent exportin. An unbiased affinity chromatography approach with immobilized pre-miRNAs identified exportin 5 as the pre-miRNA-specific export carrier. We have cloned exportin 5 from Xenopus and demonstrate that antibodies raised against the Xenopus receptor specifically block pre-miRNA export from nuclei of Xenopus oocytes. We further show that exportin 5 interacts with double-stranded RNA in a sequence-independent manner.
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26
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Ball JR, Dimaano C, Ullman KS. The RNA binding domain within the nucleoporin Nup153 associates preferentially with single-stranded RNA. RNA (NEW YORK, N.Y.) 2004; 10:19-27. [PMID: 14681581 PMCID: PMC1370514 DOI: 10.1261/rna.5109104] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2003] [Accepted: 09/22/2003] [Indexed: 05/24/2023]
Abstract
The nuclear pore protein Nup153 is important for the transport of protein and RNA between the nucleus and cytoplasm. Recently, a novel RNA binding domain (RBD) was mapped within the N-terminal region of Nup153; however, the determinants of RNA association were not characterized. Here we have tested a range of RNAs with different general features to better understand targets recognized by this domain. We have found that the RBD associates with single-stranded RNA with little sequence preference. These results provide new information about a novel RNA binding domain and suggest new models to consider for the contribution of Nup153 to nucleocytoplasmic transport.
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Affiliation(s)
- Jennifer R Ball
- Department of Oncological Sciences, Huntsman Cancer Institute, The University of Utah, Salt Lake City, Utah 84112, USA
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27
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Gwizdek C, Ossareh-Nazari B, Brownawell AM, Evers S, Macara IG, Dargemont C. Minihelix-containing RNAs mediate exportin-5-dependent nuclear export of the double-stranded RNA-binding protein ILF3. J Biol Chem 2003; 279:884-91. [PMID: 14570900 DOI: 10.1074/jbc.m306808200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The karyopherin-related nuclear transport factor exportin-5 preferentially recognizes and transports RNAs containing minihelix motif, a structural cis-acting export element that comprises a double-stranded stem (>14 nucleotides) with a base-paired 5' end and a 3-8-nucleotide protruding 3' end. This structural motif is present in various small cellular and viral polymerase III transcripts such as the adenovirus VA1 RNA (VA1). Here we show that the double-stranded RNA-binding protein, ILF3 (interleukin enhancer binding factor 3) preferentially binds minihelix motif. Gel retardation assays and glutathione S-transferase pull-down experiments revealed that ILF3, exportin-5, RanGTP, and VA1 RNA assembled in a quaternary complex in which the RNA moiety bridges the interaction between ILF3 and exportin-5. Formation of this complex is facilitated by the ability of both exportin-5 and ILF3 to mutually increase their apparent affinity for VA1 RNA. Using microinjection in the nucleus of HeLa cells and transfection experiments, we show here that formation of the cooperative RanGTP-dependent RNA/ILF3/exportin-5 complex promotes the co-transport of VA1 and ILF3 from the nucleus to the cytoplasm. Exportin-5 thus appears as the first example of a nuclear export receptor that mediates RNA export but also promotes transport of proteinaceous cargo through appropriate and specific RNA adaptors.
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Affiliation(s)
- Carole Gwizdek
- Institut Jacques Monod, Unité Mixte de Recherche 7592, CNRS, Universités Paris VI et VII, 2 Place Jussieu, Tour 43, Paris 75251 Cedex 05, France
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28
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Gwizdek C, Ossareh-Nazari B, Brownawell AM, Doglio A, Bertrand E, Macara IG, Dargemont C. Exportin-5 mediates nuclear export of minihelix-containing RNAs. J Biol Chem 2003; 278:5505-8. [PMID: 12509441 DOI: 10.1074/jbc.c200668200] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The adenovirus VA1 RNA (VA1), a 160-nucleotide (nt)-long RNA transcribed by RNA polymerase III, is efficiently exported from the nucleus to the cytoplasm of infected cells, where it antagonizes the interferon-induced antiviral defense system. We recently reported that nuclear export of VA1 is mediated by a cis-acting RNA export motif, called minihelix, that comprises a double-stranded stem (>14 nt) with a base-paired 5' end and a 3-8-nt protruding 3' end. RNA export mediated by the minihelix motif is Ran-dependent, which indicates the involvement of a karyopherin-related factor (exportin) that remained to be determined. Here we show using microinjection in Xenopus laevis oocytes that VA1 is transported to the cytoplasm by exportin-5, a nuclear transport factor for double-stranded RNA binding proteins. Gel retardation assays revealed that exportin-5 directly interacts with VA1 RNA in a RanGTP-dependent manner. More generally, in vivo and in vitro competition experiments using various VA1-derived, but also artificial and cellular, RNAs lead to the conclusion that exportin-5 preferentially recognizes and transports minihelix motif-containing RNAs.
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Affiliation(s)
- Carole Gwizdek
- Institut Jacques Monod, Unité Mixte de Recherche 7592, CNRS, Universités Paris VI et VII, 2 Place Jussieu, Tour 43, 75251 Paris Cedex 05, France
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29
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Abstract
Eukaryotic cells export several different classes of RNA molecule from the nucleus, where they are transcribed, to the cytoplasm, where the majority participate in different aspects of protein synthesis. It is now clear that these different classes of RNA, including rRNAs, tRNAs, mRNAs and snRNAs, are specifically directed into distinct but in some cases partially overlapping nuclear export pathways. All non-coding RNAs are now known to depend on members of the karyopherin family of Ran-dependent nucleocytoplasmic transport factors for their nuclear export. In contrast, mRNA export is generally mediated by a distinct, Ran-independent nuclear export pathway that is both complex and, as yet, incompletely understood. However, for all classes of RNA molecules, nuclear export is dependent on the assembly of the RNA into the appropriate ribonucleoprotein complex, and nuclear export therefore also appears to function as an important proofreading mechanism.
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Affiliation(s)
- Bryan R Cullen
- Howard Hughes Medical Institute and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
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30
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MESH Headings
- Active Transport, Cell Nucleus
- Endoribonucleases/metabolism
- Genes, Fungal
- Mitochondria/metabolism
- Models, Biological
- Nucleic Acid Conformation
- Protein Biosynthesis
- RNA Editing
- RNA Processing, Post-Transcriptional
- RNA Splicing
- RNA, Catalytic/metabolism
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Ribonuclease P
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Anita K Hopper
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
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31
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Hamm J, Alessi DR, Biondi RM. Bi-functional, substrate mimicking RNA inhibits MSK1-mediated cAMP-response element-binding protein phosphorylation and reveals magnesium ion-dependent conformational changes of the kinase. J Biol Chem 2002; 277:45793-802. [PMID: 12235136 DOI: 10.1074/jbc.m205072200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The design of specific inhibitors for protein kinases is an important step toward elucidation of intracellular signal transduction pathways and to guide drug discovery programs. We devised a model approach to generate specific, competitive kinase inhibitors by isolating substrate mimics containing two independent binding sites with an anti-idiotype strategy from combinatorial RNA libraries. As a general test for the ability to generate highly specific kinase inhibitors, we selected the transcription factor cAMP-response element-binding protein (CREB) that is phosphorylated on the same serine residue by the protein kinase MSK1 as well as by RSK1. The sequences and structures of these kinases are very similar, about 60% of their amino acids are identical. Nevertheless, we can demonstrate that the selected RNA inhibitors inhibit specifically CREB phosphorylation by MSK1 but do not affect CREB phosphorylation by RSK1. The inhibitors interact preferentially with the inactive form of MSK1. Furthermore, we demonstrate that RNA ligands can be conformation-specific probes, and this feature allowed us to describe magnesium ion-dependent conformational changes of MSK1 upon activation.
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Affiliation(s)
- Jorg Hamm
- Department of Biochemistry, University of Dundee, Dundee, United Kingdom.
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32
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Abstract
Non-natural, functional RNA molecules, such as short interfering (si) RNAs, aptazymes, maxizymes and intramers, allow modulation of gene function at the mRNA or protein level. This review discusses recent advances made in the expression and application of these functional RNAs and illustrates how engineered, intracellularly active RNAs can serve as promising tools for understanding the function of genes and their protein products or as potential therapeutic agents.
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Affiliation(s)
- Michael Famulok
- Institut für Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany.
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33
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Mougin A, Torterotot F, Branlant C, Jacobson MR, Huang Q, Pederson T. A 3'-terminal minihelix in the precursor of human spliceosomal U2 small nuclear RNA. J Biol Chem 2002; 277:23137-42. [PMID: 11956214 DOI: 10.1074/jbc.m202258200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
U2 RNA is one of five small nuclear RNAs that participate in the majority of mRNA splicing. In addition to its role in mRNA splicing, the biosynthesis of U2 RNA and three of the other spliceosomal RNAs is itself an intriguing process involving nuclear export followed by 5'-cap hypermethylation, assembly with specific proteins, 3' end processing, and then nuclear import. Previous work has identified sequences near the 3' end of pre-U2 RNA that are required for accurate and efficient processing. In this study, we have investigated the structural basis of U2 RNA 3' end processing by chemical and enzymatic probing methods. Our results demonstrate that the 3' end of pre-U2 RNA is a minihelix with an estimated stabilization free energy of -6.9 kcal/mol. Parallel RNA structure mapping experiments with mutant pre-U2 RNAs revealed that the presence of this 3' minihelix is itself not required for in vitro 3'-processing of pre-U2 RNA, in support of earlier studies implicating internal regions of pre-U2 RNA. Other considerations raise the possibility that this distinctive structural motif at the 3' end of pre-U2 RNA plays a role in the cleavage of the precursor from its longer primary transcript or in its nucleocytoplasmic traffic.
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Affiliation(s)
- Annie Mougin
- Unité Mixte Recherche 7567 CNRS-Université Henri Poincaré Nancy I, Maturation des ARN et Enzymologie Moléculaire, Université H. Poincaré, 54506 Vandoeuvre-les Nancy, France
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