1
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Clark NE, Katolik A, Gallant P, Welch A, Murphy E, Buerer L, Schorl C, Naik N, Naik MT, Holloway SP, Cano K, Weintraub ST, Howard KM, Hart PJ, Jogl G, Damha MJ, Fairbrother WG. Activation of human RNA lariat debranching enzyme Dbr1 by binding protein TTDN1 occurs though an intrinsically disordered C-terminal domain. J Biol Chem 2023; 299:105100. [PMID: 37507019 PMCID: PMC10470207 DOI: 10.1016/j.jbc.2023.105100] [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: 04/26/2023] [Revised: 07/11/2023] [Accepted: 07/20/2023] [Indexed: 07/30/2023] Open
Abstract
In eukaryotic cells, the introns are excised from pre-mRNA by the spliceosome. These introns typically have a lariat configuration due to the 2'-5' phosphodiester bond between an internal branched residue and the 5' terminus of the RNA. The only enzyme known to selectively hydrolyze the 2'-5' linkage of these lariats is the RNA lariat debranching enzyme Dbr1. In humans, Dbr1 is involved in processes such as class-switch recombination of immunoglobulin genes, and its dysfunction is implicated in viral encephalitis, HIV, ALS, and cancer. However, mechanistic details of precisely how Dbr1 affects these processes are missing. Here we show that human Dbr1 contains a disordered C-terminal domain through sequence analysis and nuclear magnetic resonance. This domain stabilizes Dbr1 in vitro by reducing aggregation but is dispensable for debranching activity. We establish that Dbr1 requires Fe2+ for efficient catalysis and demonstrate that the noncatalytic protein Drn1 and the uncharacterized protein trichothiodystrophy nonphotosensitive 1 directly bind to Dbr1. We demonstrate addition of trichothiodystrophy nonphotosensitive 1 to in vitro debranching reactions increases the catalytic efficiency of human Dbr1 19-fold but has no effect on the activity of Dbr1 from the amoeba Entamoeba histolytica, which lacks a disordered C-terminal domain. Finally, we systematically examine how the identity of the branchpoint nucleotide affects debranching rates. These findings describe new aspects of Dbr1 function in humans and further clarify how Dbr1 contributes to human health and disease.
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Affiliation(s)
- Nathaniel E Clark
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA.
| | - Adam Katolik
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Pascal Gallant
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Anastasia Welch
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Eileen Murphy
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Luke Buerer
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Christoph Schorl
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Nandita Naik
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Mandar T Naik
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Stephen P Holloway
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Kristin Cano
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Susan T Weintraub
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Katherine M Howard
- Department of Biomedical Sciences, School of Dental Medicine, University of Nevada-Las Vegas, Las Vegas, Nevada, USA
| | - P John Hart
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Gerwald Jogl
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, Quebec, Canada.
| | - William G Fairbrother
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA.
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2
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Clark NE, Katolik A, Welch A, Schorl C, Holloway SP, Schuermann JP, Hart PJ, Taylor AB, Damha MJ, Fairbrother WG. Crystal Structure of the RNA Lariat Debranching Enzyme Dbr1 with Hydrolyzed Phosphorothioate RNA Product. Biochemistry 2022; 61:2933-2939. [PMID: 36484984 DOI: 10.1021/acs.biochem.2c00590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The RNA lariat debranching enzyme is the sole enzyme responsible for hydrolyzing the 2'-5' phosphodiester bond in RNA lariats produced by the spliceosome. Here, we test the ability of Dbr1 to hydrolyze branched RNAs (bRNAs) that contain a 2'-5'-phosphorothioate linkage, a modification commonly used to resist degradation. We attempted to cocrystallize a phosphorothioate-branched RNA (PS-bRNA) with wild-type Entamoeba histolytica Dbr1 (EhDbr1) but observed in-crystal hydrolysis of the phosphorothioate bond. The crystal structure revealed EhDbr1 in a product-bound state, with the hydrolyzed 2'-5' fragment of the PS-bRNA mimicking the binding mode of the native bRNA substrate. These findings suggest that product inhibition may contribute to the kinetic mechanism of Dbr1. We show that Dbr1 enzymes cleave phosphorothioate linkages at rates ∼10,000-fold more slowly than native phosphate linkages. This new product-bound crystal structure offers atomic details, which can aid inhibitor design. Dbr1 inhibitors could be therapeutic or investigative compounds for human diseases such as human immunodeficiency virus (HIV), amyotrophic lateral sclerosis (ALS), cancer, and viral encephalitis.
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Affiliation(s)
- Nathaniel E. Clark
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02891, United States
| | - Adam Katolik
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Anastasia Welch
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02891, United States
| | - Christoph Schorl
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02891, United States
| | - Stephen P. Holloway
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas 78229, United States
| | - Jonathan P. Schuermann
- Northeastern Collaborative Access Team, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - P. John Hart
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas 78229, United States
| | - Alexander B. Taylor
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas 78229, United States
| | - Masad J. Damha
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - William G. Fairbrother
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02891, United States
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3
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Pedersen SF, Collora JA, Kim RN, Yang K, Razmi A, Catalano AA, Yeh YHJ, Mounzer K, Tebas P, Montaner LJ, Ho YC. Inhibition of a Chromatin and Transcription Modulator, SLTM, Increases HIV-1 Reactivation Identified by a CRISPR Inhibition Screen. J Virol 2022; 96:e0057722. [PMID: 35730977 PMCID: PMC9278143 DOI: 10.1128/jvi.00577-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/27/2022] [Indexed: 12/24/2022] Open
Abstract
Despite effective antiretroviral therapy, HIV-1 persistence in latent reservoirs remains a major obstacle to a cure. We postulate that HIV-1 silencing factors suppress HIV-1 reactivation and that inhibition of these factors will increase HIV-1 reactivation. To identify HIV-1 silencing factors, we conducted a genome-wide CRISPR inhibition (CRISPRi) screen using four CRISPRi-ready, HIV-1-d6-GFP-infected Jurkat T cell clones with distinct integration sites. We sorted cells with increased green fluorescent protein (GFP) expression and captured single guide RNAs (sgRNAs) via targeted deep sequencing. We identified 18 HIV-1 silencing factors that were significantly enriched in HIV-1-d6-GFPhigh cells. Among them, SLTM (scaffold attachment factor B-like transcription modulator) is an epigenetic and transcriptional modulator having both DNA and RNA binding capacities not previously known to affect HIV-1 transcription. Knocking down SLTM by CRISPRi significantly increased HIV-1-d6-GFP expression (by 1.9- to 4.2-fold) in three HIV-1-d6-GFP-Jurkat T cell clones. Furthermore, SLTM knockdown increased the chromatin accessibility of HIV-1 and the gene in which HIV-1 is integrated but not the housekeeping gene POLR2A. To test whether SLTM inhibition can reactivate HIV-1 and further induce cell death of HIV-1-infected cells ex vivo, we established a small interfering RNA (siRNA) knockdown method that reduced SLTM expression in CD4+ T cells from 10 antiretroviral therapy (ART)-treated, virally suppressed, HIV-1-infected individuals ex vivo. Using limiting dilution culture, we found that SLTM knockdown significantly reduced the frequency of HIV-1-infected cells harboring inducible HIV-1 by 62.2% (0.56/106 versus 1.48/106 CD4+ T cells [P = 0.029]). Overall, our study indicates that SLTM inhibition reactivates HIV-1 in vitro and induces cell death of HIV-1-infected cells ex vivo. Our study identified SLTM as a novel therapeutic target. IMPORTANCE HIV-1-infected cells, which can survive drug treatment and immune cell killing, prevent an HIV-1 cure. Immune recognition of infected cells requires HIV-1 protein expression; however, HIV-1 protein expression is limited in infected cells after long-term therapy. The ways in which the HIV-1 provirus is blocked from producing protein are unknown. We identified a new host protein that regulates HIV-1 gene expression. We also provided a new method of studying HIV-1-host factor interactions in cells from infected individuals. These improvements may enable future strategies to reactivate HIV-1 in infected individuals so that infected cells can be killed by immune cells, drug treatment, or the virus itself.
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Affiliation(s)
- Savannah F. Pedersen
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Jack A. Collora
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Rachel N. Kim
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Kerui Yang
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Anya Razmi
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Allison A. Catalano
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Yang-Hui Jimmy Yeh
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Karam Mounzer
- Philadelphia FIGHT Community Health Centers, Philadelphia, Pennsylvania, USA
| | - Pablo Tebas
- Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | - Ya-Chi Ho
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA
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4
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Clark NE, Katolik A, Taggart AJ, Buerer L, Holloway SP, Miller N, Phillips JD, Farrell CP, Damha MJ, Fairbrother WG. Metal content and kinetic properties of yeast RNA lariat debranching enzyme Dbr1. RNA (NEW YORK, N.Y.) 2022; 28:927-936. [PMID: 35459748 PMCID: PMC9202583 DOI: 10.1261/rna.079159.122] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/11/2022] [Indexed: 06/14/2023]
Abstract
In eukaryotic cells, intron lariats produced by the spliceosome contain a 2'5' phosphodiester linkage. The RNA lariat debranching enzyme, Dbr1, is the only enzyme known to hydrolyze this bond. Dbr1 is a member of the metallophosphoesterase (MPE) family of enzymes, and recent X-ray crystal structures and biochemistry data demonstrate that Dbr1 from Entamoeba histolytica uses combinations of Mn2+, Zn2+, and Fe2+ as enzymatic cofactors. Here, we examine the kinetic properties and metal dependence of the Dbr1 homolog from Saccharomyces cerevisiae (yDbr1). Elemental analysis measured stoichiometric quantities of Fe and Zn in yDbr1 purified following heterologous expression E. coli We analyzed the ability of Fe2+, Zn2+, and Mn2+ to reconstitute activity in metal-free apoenzyme. Purified yDbr1 was highly active, turning over substrate at 5.6 sec-1, and apo-yDbr1 reconstituted with Fe2+ was the most active species, turning over at 9.2 sec-1 We treated human lymphoblastoid cells with the iron-chelator deferoxamine and measured a twofold increase in cellular lariats. These data suggest that Fe is an important biological cofactor for Dbr1 enzymes.
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Affiliation(s)
- Nathaniel E Clark
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Adam Katolik
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Allison J Taggart
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
- Raytheon BBN Technologies, Cambridge, Massachusetts 02138, USA
| | - Luke Buerer
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
| | - Stephen P Holloway
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | - Nathaniel Miller
- Department of Geological Sciences, University of Texas Austin, Austin, Texas 78712, USA
| | - John D Phillips
- Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA
| | - Colin P Farrell
- Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - William G Fairbrother
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
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5
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Soobramoney C, Parboosing R. siRNAs and viruses: The good, the bad and the way forward. Curr Mol Pharmacol 2021; 15:143-158. [PMID: 33881977 DOI: 10.2174/1874467214666210420113427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 01/08/2021] [Accepted: 02/08/2021] [Indexed: 11/22/2022]
Abstract
There are no available antivirals for many viruses or strains, while current antivirals are limited by toxicity and drug resistance. Therefore, alternative strategies, such as RNA interference (RNAi) are required. RNAi suppresses gene expression of any mRNA, making it an attractive candidate for antiviral therapeutics. Studies have evaluated siRNAs in a range of viruses, with some showing promising results. However, issues with stability and delivery of siRNAs remain. These may be minimized by modifying the siRNA structure, using an efficient delivery vector and targeting multiple regions of a virus's genome in a single dose. Finding these solutions could accelerate the progress of RNAi-based antivirals. This review highlights selected examples of antiviral siRNAs, limitations of RNAi and strategies to overcome these limitations.
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Affiliation(s)
| | - Raveen Parboosing
- Department of Virology, University of KwaZulu Natal/ National Health Laboratory Services, Durban, South Africa
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6
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Menees TM. Saccharomyces cerevisiae RNA lariat debranching enzyme, Dbr1p, is required for completion of reverse transcription by the retrovirus-like element Ty1 and cleaves branched Ty1 RNAs. Mol Genet Genomics 2021; 296:409-422. [PMID: 33464395 DOI: 10.1007/s00438-020-01753-y] [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: 08/31/2020] [Accepted: 12/14/2020] [Indexed: 11/25/2022]
Abstract
RNA debranching enzymes are 2'-5' phosphodiesterases found in all eukaryotes. Their main role is cleavage of intron RNA lariat branch points, promoting RNA turnover via exonucleases. Consistent with this role, cells with reduced RNA debranching enzyme activity accumulate intron RNA lariats. The Saccharomyces cerevisiae RNA debranching enzyme Dbr1p is also a host factor for the yeast long terminal repeat (LTR) retrotransposon Ty1, a model for many aspects of retroviral replication. Fittingly, the human RNA debranching enzyme Dbr1 is a host factor for the human immunodeficiency virus, HIV-1. The yeast and human RNA debranching enzymes act at the reverse transcription stages for Ty1 and HIV-1, respectively. Although efficient production of full-length Ty1 cDNA requires Dbr1p, the findings reported here indicate that production of the earliest distinct cDNA product, minus strand strong stop DNA (-sssDNA), is equivalent in wild type and dbr1∆ mutant cells. Several branched Ty1 RNAs are shown to accumulate in dbr1∆ cells during retrotransposition. These data are consistent with creation of Ty1 RNA branches prior to Ty1 reverse transcription and their removal by Dbr1p to allow efficient extension of early cDNA products. The data support the possibility that RNA branch formation and cleavage play broadly shared, but unknown roles in retroviral and LTR retrotransposon reverse transcription.
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Affiliation(s)
- Thomas M Menees
- School of Biological and Chemical Sciences, University of Missouri-Kansas City, Kansas City, MO, USA.
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7
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Mohanta A, Chakrabarti K. Dbr1 functions in mRNA processing, intron turnover and human diseases. Biochimie 2020; 180:134-142. [PMID: 33038423 DOI: 10.1016/j.biochi.2020.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/01/2020] [Accepted: 10/05/2020] [Indexed: 12/29/2022]
Abstract
Pre-mRNA processing and mRNA stability play direct roles in controlling protein abundance in a cell. Before the mRNA can be translated into a protein, the introns in the pre-mRNA transcripts need to be removed by splicing, such that exons can be ligated together and can code for a protein. In this process, the function of the RNA lariat debranching enzyme or Dbr1 provides a rate-limiting step in the intron turnover process and possibly regulating the production of translation competent mRNAs. Surprising new roles of Dbr1 are emerging in cellular metabolism which extends beyond intron turnover processes, ranging from splicing regulation to translational control. In this review, we highlight the importance of the Dbr1 enzyme, its structure and how anomalies in its function could relate to various human diseases.
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Affiliation(s)
- Arundhati Mohanta
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
| | - Kausik Chakrabarti
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, 28223, USA.
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8
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Abstract
Host cell factors are integral to viral replication. Human immunodeficiency virus 1 (HIV-1), the retroviral agent of acquired immune deficiency syndrome, requires several host factors for reverse transcription of the viral genomic RNA (gRNA) into DNA shortly after viral entry. One of these host factors is the RNA lariat debranching enzyme (Dbr1), which cleaves the 2'-5' bond of branched and lariat RNAs. A recent study has revealed that Dbr1 cleaves HIV-1 gRNA lariats that form early after viral entry. Without Dbr1 activity, HIV-1 reverse transcription stalls, consistent with blockage of viral reverse transcriptase at gRNA branch points. These findings echo an earlier study with the long-terminal-repeat retrotransposon of Saccharomyces cerevisiae, Ty1, which is a retrovirus model. Currently, branching and debranching of viral gRNA are not widely recognized as features of HIV-1 replication, and the role of a gRNA lariat is not known. Future studies will determine whether these gRNA dynamics represent fundamental features of retroviral biology and whether they occur for other positive-sense RNA viruses.
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Affiliation(s)
- Thomas M Menees
- School of Biological and Chemical Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA;
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9
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Huang YL, Kawai G, Hasegawa A, Kannagi M, Masuda T. Impact of 5'-end nucleotide modifications of HIV-1 genomic RNA on reverse transcription. Biochem Biophys Res Commun 2019; 516:1145-1151. [PMID: 31284953 DOI: 10.1016/j.bbrc.2019.06.152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 06/27/2019] [Indexed: 11/20/2022]
Abstract
Reverse transcription of retroviral RNA is accomplished through a minus-strand strong stop cDNA (-sscDNA) synthesis and subsequent strand-transfer reactions. We have previously reported a critical role of guanosine (G) number at 5'-terminal of HIV-1 RNA for successful strand-transfer of -sscDNA. In this study, role(s) of the cap consisting of 7-methyl guanosine (7mG), a hallmark of transcripts generated by RNA polymerase II, at the 5'-end G nucleotide (5'-G) of HIV-1 RNA were examined. In parallel, contribution of highly conserved GGG tract located at the U3/R boundary in 3' terminal region of viral RNA (3'-GGG tract) was also addressed. The in vitro reverse transcription analysis using synthetic HIV-1 RNAs possessing the 5'-G with cap or triphosphate form demonstrated that the 5'-cap significantly increased strand-transfer efficiency of -sscDNA. Meanwhile, effect of the 5'-cap on the strand-transfer was retained in the reaction using mutant HIV-1 RNAs in which two Gs were deleted from the 3'-GGG tract. Lack of apparent contribution of the 3'-GGG tract during strand-transfer events in vitro was reproduced in the context of HIV-1 replication within cells. Instead, we noticed that the 3'-GGG tract might be required for efficient gene expression from proviral DNA. These results indicated that 7mG of the cap on HIV-1 RNA might not be reverse-transcribed and a possible role of the 3'-GGG tract to accept the non-template nucleotide addition during -sscDNA synthesis might be less likely. The 5'-G modifications of HIV-1 RNAs by the cap- or phosphate-removal enzyme revealed that the cap or monophosphate form of the 5'-G was preferred for the 1st strand-transfer compared to the triphosphate or non-phosphate form. Taken together, a status of the 5'-G determined strand-transfer efficiency of -sscDNA without affecting the non-template nucleotide addition, probably by affecting association of the 5'-G with 3'-end region of viral RNA.
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Affiliation(s)
- Yu-Lun Huang
- Department of Immunotherapeutics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima, 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Gota Kawai
- Department of Life Science, Faculty of Advanced Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino-shi, Chiba, 275-0016, Japan
| | - Atsuhiko Hasegawa
- Department of Immunotherapeutics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima, 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Mari Kannagi
- Department of Immunotherapeutics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima, 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan
| | - Takao Masuda
- Department of Immunotherapeutics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima, 1-5-45, Bunkyo-ku, Tokyo, 113-8519, Japan.
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10
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Zhang X, Zhang Y, Wang T, Li Z, Cheng J, Ge H, Tang Q, Chen K, Liu L, Lu C, Guo J, Zheng B, Zheng Y. A Comprehensive Map of Intron Branchpoints and Lariat RNAs in Plants. THE PLANT CELL 2019; 31:956-973. [PMID: 30894459 PMCID: PMC6533014 DOI: 10.1105/tpc.18.00711] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 01/29/2019] [Accepted: 03/14/2019] [Indexed: 05/20/2023]
Abstract
Lariats are formed by excised introns, when the 5' splice site joins with the branchpoint (BP) during splicing. Although lariat RNAs are usually degraded by RNA debranching enzyme 1, recent findings in animals detected many lariat RNAs under physiological conditions. By contrast, the features of BPs and to what extent lariat RNAs accumulate naturally are largely unexplored in plants. Here, we analyzed 948 RNA sequencing data sets to document plant BPs and lariat RNAs on a genome-wide scale. In total, we identified 13,872, 5199, 29,582, and 13,478 BPs in Arabidopsis (Arabidopsis thaliana), tomato (Solanum lycopersicum), rice (Oryza sativa), and maize (Zea mays), respectively. Features of plant BPs are highly similar to those in yeast and human, in that BPs are adenine-preferred and flanked by uracil-enriched sequences. Intriguingly, ∼20% of introns harbor multiple BPs, and BP usage is tissue-specific. Furthermore, 10,580 lariat RNAs accumulate in wild-type Arabidopsis plants, and most of these lariat RNAs originate from longer or retroelement-depleted introns. Moreover, the expression of these lariat RNAs is accompanied by the incidence of back-splicing of parent exons. Collectively, our results provide a comprehensive map of intron BPs and lariat RNAs in four plant species and uncover a link between lariat turnover and splicing.
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Affiliation(s)
- Xiaotuo Zhang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
| | - Yong Zhang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Taiyun Wang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Ziwei Li
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Jinping Cheng
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Haoran Ge
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Qi Tang
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Kun Chen
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
| | - Li Liu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
| | - Chenyu Lu
- Yunnan Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
| | - Junqiang Guo
- Yunnan Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
- Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
| | - Binglian Zheng
- State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Yun Zheng
- Yunnan Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
- Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
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11
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Conformational Changes in the 5' End of the HIV-1 Genome Dependent on the Debranching Enzyme DBR1 during Early Stages of Infection. J Virol 2017; 91:JVI.01377-17. [PMID: 28931690 DOI: 10.1128/jvi.01377-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 09/18/2017] [Indexed: 11/20/2022] Open
Abstract
Previous studies in our laboratory showed that the RNA debranching enzyme (DBR1) is not required for early steps in HIV cDNA formation but is necessary for synthesis of intermediate and late cDNA products. To further characterize this effect, we evaluated the topology of the 5' end of the HIV-1 RNA genome during early infection with and without inhibition of DBR1 synthesis. Cells were transfected with DBR1 short hairpin RNA (shRNA) followed 48 h later by infection with an HIV-1-derived vector containing an RNase H-deficient reverse transcriptase (RT). RNA was isolated at several times postinfection and treated with various RNA-modifying enzymes prior to rapid amplification of 5' cDNA ends (5' RACE) for HIV-1 RNA and quantitative reverse transcriptase PCR (qRT-PCR). In infected cells, DBR1 knockdown inhibited detection of free HIV-1 RNA 5' ends at all time points. The difference in detection of free HIV-1 RNA 5' ends in infected DBR1 knockdown versus control cells was eliminated by in vitro incubation of infected cell RNAs with yeast or human DBR1 enzyme prior to 5' RACE and qRT-PCR. This was dependent on the 2'-5' phosphatase activity of DBR1, since it did not occur when we used the catalytically inactive DBR1(N85A) mutant. Finally, HIV-1 RNA from infected DBR1 knockdown cells was resistant to RNase R that degrades linear RNAs but not RNAs in circular or lariat-like conformations. These results provide evidence for formation of a lariat-like structure involving the 5' end of HIV-1 RNA during an early step in infection and the involvement of DBR1 in resolving it.IMPORTANCE Our findings support a new view of the early steps in HIV genome replication. We show that the HIV genomic RNA is rapidly decapped and forms a lariat-like structure after entering a cell. The lariat-like structure is subsequently resolved by the cellular enzyme DBR1, leaving a 5' phosphate. This pathway is similar to the formation and resolution of pre-mRNA intron lariats and therefore suggests that similar mechanisms may be used by HIV. Our work therefore opens a new area of investigation in HIV replication and may ultimately uncover new targets for inhibiting HIV replication and for preventing the development of AIDS.
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12
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Döring J, Hurek T. Arm-specific cleavage and mutation during reverse transcription of 2΄,5΄-branched RNA by Moloney murine leukemia virus reverse transcriptase. Nucleic Acids Res 2017; 45:3967-3984. [PMID: 28160599 PMCID: PMC5399748 DOI: 10.1093/nar/gkx073] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 01/30/2017] [Indexed: 11/14/2022] Open
Abstract
Branchpoint nucleotides of intron lariats induce pausing of DNA synthesis by reverse transcriptases (RTs), but it is not known yet how they direct RT RNase H activity on branched RNA (bRNA). Here, we report the effects of the two arms of bRNA on branchpoint-directed RNA cleavage and mutation produced by Moloney murine leukemia virus (M-MLV) RT during DNA polymerization. We constructed a long-chained bRNA template by splinted-ligation. The bRNA oligonucleotide is chimeric and contains DNA to identify RNA cleavage products by probe hybridization. Unique sequences surrounding the branchpoint facilitate monitoring of bRNA purification by terminal-restriction fragment length polymorphism analysis. We evaluate the M-MLV RT-generated cleavage and mutational patterns. We find that cleavage of bRNA and misprocessing of the branched nucleotide proceed arm-specifically. Bypass of the branchpoint from the 2΄-arm causes single-mismatch errors, whereas bypass from the 3΄-arm leads to deletion mutations. The non-template arm is cleaved when reverse transcription is primed from the 3΄-arm but not from the 2΄-arm. This suggests that RTs flip ∼180° at branchpoints and RNases H cleave the non-template arm depending on its accessibility. Our observed interplay between M-MLV RT and bRNA would be compatible with a bRNA-mediated control of retroviral and related retrotransposon replication.
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Affiliation(s)
- Jessica Döring
- Department of Microbe-Plant Interactions, CBIB (Center for Biomolecular Interactions Bremen), University of Bremen, PO Box 330440, D-28334 Bremen, Germany
| | - Thomas Hurek
- Department of Microbe-Plant Interactions, CBIB (Center for Biomolecular Interactions Bremen), University of Bremen, PO Box 330440, D-28334 Bremen, Germany
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13
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Ransey E, Paredes E, Dey SK, Das SR, Heroux A, Macbeth MR. Crystal structure of the Entamoeba histolytica RNA lariat debranching enzyme EhDbr1 reveals a catalytic Zn 2+ /Mn 2+ heterobinucleation. FEBS Lett 2017; 591:2003-2010. [PMID: 28504306 DOI: 10.1002/1873-3468.12677] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/03/2017] [Accepted: 05/05/2017] [Indexed: 01/24/2023]
Abstract
The RNA lariat debranching enzyme, Dbr1, is a metallophosphoesterase that cleaves 2'-5' phosphodiester bonds within intronic lariats. Previous reports have indicated that Dbr1 enzymatic activity is supported by diverse metal ions including Ni2+ , Mn2+ , Mg2+ , Fe2+ , and Zn2+ . While in initial structures of the Entamoeba histolytica Dbr1 only one of the two catalytic metal-binding sites were observed to be occupied (with a Mn2+ ion), recent structures determined a Zn2+ /Fe2+ heterobinucleation. We solved a high-resolution X-ray crystal structure (1.8 Å) of the E. histolytica Dbr1 and determined a Zn2+ /Mn2+ occupancy. ICP-AES corroborate this finding, and in vitro debranching assays with fluorescently labeled branched substrates confirm activity.
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Affiliation(s)
- Elizabeth Ransey
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Eduardo Paredes
- Department of Chemistry and Center for Nucleic Acids & Technology, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Sourav K Dey
- Department of Chemistry and Center for Nucleic Acids & Technology, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Subha R Das
- Department of Chemistry and Center for Nucleic Acids & Technology, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Annie Heroux
- National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY, USA
| | - Mark R Macbeth
- Department of Chemistry and Biochemistry, Butler University, Indianapolis, IN, USA
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14
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Katolik A, Clark NE, Tago N, Montemayor EJ, Hart PJ, Damha MJ. Fluorescent Branched RNAs for High-Throughput Analysis of Dbr1 Enzyme Kinetics and Inhibition. ACS Chem Biol 2017; 12:622-627. [PMID: 28055181 DOI: 10.1021/acschembio.6b00971] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have developed fluorescent 2',5' branched RNAs (bRNA) that permit real time monitoring of RNA lariat (intron) debranching enzyme (Dbr1) kinetics. These compounds contain fluorescein (FAM) on the 5' arm of the bRNA that is quenched by a dabcyl moiety on the 2' arm. Dbr1-mediated hydrolysis of the 2',5' linkage induces a large increase in fluorescence, providing a convenient assay for Dbr1 hydrolysis. We show that unlabeled bRNAs with non-native 2',5'-phosphodiester linkages, such as phosphoramidate or phosphorothioate, can inhibit Dbr1-mediated debranching with IC50 values in the low nanomolar range. In addition to measuring kinetic parameters of the debranching enzyme, these probes can be used for high throughput screening (HTS) of chemical libraries with the aim of identifying Dbr1 inhibitors, compounds that may be useful in treating neurodegenerative diseases and retroviral infections.
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Affiliation(s)
- Adam Katolik
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
| | - Nathaniel E. Clark
- Department
of Biochemistry and Structural Biology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78229, United States
| | - Nobuhiro Tago
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
| | - Eric J. Montemayor
- Departments
of Biochemistry and Biomolecular Chemistry, University Of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - P. John Hart
- Department
of Biochemistry and Structural Biology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78229, United States
- Department
of Veterans Affairs, South Texas Veterans Health Care System, San Antonio, Texas 78229, United States
| | - Masad J. Damha
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
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15
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Metal dependence and branched RNA cocrystal structures of the RNA lariat debranching enzyme Dbr1. Proc Natl Acad Sci U S A 2016; 113:14727-14732. [PMID: 27930312 DOI: 10.1073/pnas.1612729114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intron lariats are circular, branched RNAs (bRNAs) produced during pre-mRNA splicing. Their unusual chemical and topological properties arise from branch-point nucleotides harboring vicinal 2',5'- and 3',5'-phosphodiester linkages. The 2',5'-bonds must be hydrolyzed by the RNA debranching enzyme Dbr1 before spliced introns can be degraded or processed into small nucleolar RNA and microRNA derived from intronic RNA. Here, we measure the activity of Dbr1 from Entamoeba histolytica by using a synthetic, dark-quenched bRNA substrate that fluoresces upon hydrolysis. Purified enzyme contains nearly stoichiometric equivalents of Fe and Zn per polypeptide and demonstrates turnover rates of ∼3 s-1 Similar rates are observed when apo-Dbr1 is reconstituted with Fe(II)+Zn(II) under aerobic conditions. Under anaerobic conditions, a rate of ∼4.0 s-1 is observed when apoenzyme is reconstituted with Fe(II). In contrast, apo-Dbr1 reconstituted with Mn(II) or Fe(II) under aerobic conditions is inactive. Diffraction data from crystals of purified enzyme using X-rays tuned to the Fe absorption edge show Fe partitions primarily to the β-pocket and Zn to the α-pocket. Structures of the catalytic mutant H91A in complex with 7-mer and 16-mer synthetic bRNAs reveal bona fide RNA branchpoints in the Dbr1 active site. A bridging hydroxide is in optimal position for nucleophilic attack of the scissile phosphate. The results clarify uncertainties regarding structure/function relationships in Dbr1 enzymes, and the fluorogenic probe permits high-throughput screening for inhibitors that may hold promise as treatments for retroviral infections and neurodegenerative disease.
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16
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Abstract
The enzyme reverse transcriptase (RT) was discovered in retroviruses almost 50 years ago. The demonstration that other types of viruses, and what are now called retrotransposons, also replicated using an enzyme that could copy RNA into DNA came a few years later. The intensity of the research in both the process of reverse transcription and the enzyme RT was greatly stimulated by the recognition, in the mid-1980s, that human immunodeficiency virus (HIV) was a retrovirus and by the fact that the first successful anti-HIV drug, azidothymidine (AZT), is a substrate for RT. Although AZT monotherapy is a thing of the past, the most commonly prescribed, and most successful, combination therapies still involve one or both of the two major classes of anti-RT drugs. Although the basic mechanics of reverse transcription were worked out many years ago, and the first high-resolution structures of HIV RT are now more than 20 years old, we still have much to learn, particularly about the roles played by the host and viral factors that make the process of reverse transcription much more efficient in the cell than in the test tube. Moreover, we are only now beginning to understand how various host factors that are part of the innate immunity system interact with the process of reverse transcription to protect the host-cell genome, the host cell, and the whole host, from retroviral infection, and from unwanted retrotransposition.
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17
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Bertelsen B, Nazaryan-Petersen L, Sun W, Mehrjouy MM, Xie G, Chen W, Hjermind LE, Taschner PEM, Tümer Z. A germline chromothripsis event stably segregating in 11 individuals through three generations. Genet Med 2015; 18:494-500. [PMID: 26312826 DOI: 10.1038/gim.2015.112] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 07/01/2015] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Parentally transmitted germ-line chromothripsis (G-CTH) has been identified in only a few cases. Most of these rearrangements were stably transmitted, in an unbalanced form, from a healthy mother to her child with congenital abnormalities probably caused by de novo copy-number changes of dosage sensitive genes. We describe a G-CTH transmitted through three generations in 11 healthy carriers. METHODS Conventional cytogenetic analysis, mate-pair sequencing, and polymerase chain reaction (PCR) were used to identify the chromosome rearrangement and characterize the breakpoints in all three generations. RESULTS We identified an apparently balanced translocation t(3;5), later shown to be a G-CTH, in all individuals of a three-generation family. The G-CTH stably segregated without occurrence of additional rearrangements; however, several spontaneous abortions were reported, possibly due to unbalanced transmission. Although seven protein-coding genes are interrupted, no clinical features can be definitively attributed to the affected genes. However, it can be speculated that truncation of one of these genes, encoding ataxia-telangiectasia and Rad3-related protein kinase (ATR), a key component of the DNA damage response, may be related to G-CTH formation. CONCLUSION G-CTH rearrangements are not always associated with abnormal phenotypes and may be misinterpreted as balanced two-way translocations, suggesting that G-CTH is an underdiagnosed phenomenon.Genet Med 18 5, 494-500.
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Affiliation(s)
- Birgitte Bertelsen
- Department of Clinical Genetics, Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
| | - Lusine Nazaryan-Petersen
- Department of Clinical Genetics, Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
| | - Wei Sun
- Max Delbrück Center for Molecular Medicine, Berlin Institute for Medical Systems Biology, Berlin, Germany
| | - Mana M Mehrjouy
- Wilhelm Johannsen Centre for Functional Genome Research, Department of Cellular and Molecular Medicine, Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark
| | - Gangcai Xie
- Max Delbrück Center for Molecular Medicine, Berlin Institute for Medical Systems Biology, Berlin, Germany
| | - Wei Chen
- Max Delbrück Center for Molecular Medicine, Berlin Institute for Medical Systems Biology, Berlin, Germany
| | - Lena E Hjermind
- Neurogenetics Clinic, Danish Dementia Research Centre, Department of Neurology, Rigshospitalet, and Department of Cellular and Molecular Medicine, Section of Neurogenetics, University of Copenhagen, Copenhagen, Denmark
| | - Peter E M Taschner
- Generade Center of Expertise Genomics; University of Applied Sciences Leiden, Leiden, The Netherlands
| | - Zeynep Tümer
- Department of Clinical Genetics, Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
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18
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Abstract
Long-terminal repeat (LTR)-retrotransposons generate a copy of their DNA (cDNA) by reverse transcription of their RNA genome in cytoplasmic nucleocapsids. They are widespread in the eukaryotic kingdom and are the evolutionary progenitors of retroviruses [1]. The Ty1 element of the budding yeast Saccharomyces cerevisiae was the first LTR-retrotransposon demonstrated to mobilize through an RNA intermediate, and not surprisingly, is the best studied. The depth of our knowledge of Ty1 biology stems not only from the predominance of active Ty1 elements in the S. cerevisiae genome but also the ease and breadth of genomic, biochemical and cell biology approaches available to study cellular processes in yeast. This review describes the basic structure of Ty1 and its gene products, the replication cycle, the rapidly expanding compendium of host co-factors known to influence retrotransposition and the nature of Ty1's elaborate symbiosis with its host. Our goal is to illuminate the value of Ty1 as a paradigm to explore the biology of LTR-retrotransposons in multicellular organisms, where the low frequency of retrotransposition events presents a formidable barrier to investigations of retrotransposon biology.
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Katolik A, Johnsson R, Montemayor E, Lackey JG, Hart PJ, Damha MJ. Regiospecific solid-phase synthesis of branched oligoribonucleotides that mimic intronic lariat RNA intermediates. J Org Chem 2014; 79:963-75. [PMID: 24401015 DOI: 10.1021/jo4024182] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have developed new solid phase methods for the synthesis of branched RNAs that mimic intronic lariat RNA intermediates. These methods produce branched oligoribonucleotide sequences of arbitrary length, base composition, and regiochemistry at the branchpoint junction. The methods utilize branching monomers that allow for the growth of each branch regioselectively from any of the hydroxyl positions (5′, 3′, or 2′) at the branch-point junction. The integrity and branchpoint connectivity of the synthetic products have been confirmed by HPLC and MS analysis, and cleavage of the 2′,5′ linkage by recombinant debranching enzyme. Nonhydrolyzable branched RNA analogues containing arabinose instead of ribose at the branchpoint junction were shown to inhibit debranching activity and, hence, represent “decoys” for sequestering RNA binding proteins thought to drive amyotrophic lateral sclerosis (ALS).
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20
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Montemayor EJ, Katolik A, Clark NE, Taylor AB, Schuermann JP, Combs DJ, Johnsson R, Holloway SP, Stevens SW, Damha MJ, Hart PJ. Structural basis of lariat RNA recognition by the intron debranching enzyme Dbr1. Nucleic Acids Res 2014; 42:10845-55. [PMID: 25123664 PMCID: PMC4176325 DOI: 10.1093/nar/gku725] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The enzymatic processing of cellular RNA molecules requires selective recognition of unique chemical and topological features. The unusual 2',5'-phosphodiester linkages in RNA lariats produced by the spliceosome must be hydrolyzed by the intron debranching enzyme (Dbr1) before they can be metabolized or processed into essential cellular factors, such as snoRNA and miRNA. Dbr1 is also involved in the propagation of retrotransposons and retroviruses, although the precise role played by the enzyme in these processes is poorly understood. Here, we report the first structures of Dbr1 alone and in complex with several synthetic RNA compounds that mimic the branchpoint in lariat RNA. The structures, together with functional data on Dbr1 variants, reveal the molecular basis for 2',5'-phosphodiester recognition and explain why the enzyme lacks activity toward 3',5'-phosphodiester linkages. The findings illuminate structure/function relationships in a unique enzyme that is central to eukaryotic RNA metabolism and set the stage for the rational design of inhibitors that may represent novel therapeutic agents to treat retroviral infections and neurodegenerative disease.
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Affiliation(s)
- Eric J Montemayor
- Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229, USA X-ray Crystallography Core Laboratory, The University of Texas Health Science Center, San Antonio, TX 78229, USA
| | - Adam Katolik
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Nathaniel E Clark
- Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229, USA X-ray Crystallography Core Laboratory, The University of Texas Health Science Center, San Antonio, TX 78229, USA
| | - Alexander B Taylor
- Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229, USA X-ray Crystallography Core Laboratory, The University of Texas Health Science Center, San Antonio, TX 78229, USA
| | - Jonathan P Schuermann
- Northeastern Collaborative Access Team, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - D Joshua Combs
- Program in Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78212, USA
| | - Richard Johnsson
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Stephen P Holloway
- Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229, USA
| | - Scott W Stevens
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - P John Hart
- Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229, USA X-ray Crystallography Core Laboratory, The University of Texas Health Science Center, San Antonio, TX 78229, USA Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, San Antonio, TX 78229, USA
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21
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Bitton DA, Rallis C, Jeffares DC, Smith GC, Chen YYC, Codlin S, Marguerat S, Bähler J. LaSSO, a strategy for genome-wide mapping of intronic lariats and branch points using RNA-seq. Genome Res 2014; 24:1169-79. [PMID: 24709818 PMCID: PMC4079972 DOI: 10.1101/gr.166819.113] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Both canonical and alternative splicing of RNAs are governed by intronic sequence elements and produce transient lariat structures fastened by branch points within introns. To map precisely the location of branch points on a genomic scale, we developed LaSSO (Lariat Sequence Site Origin), a data-driven algorithm which utilizes RNA-seq data. Using fission yeast cells lacking the debranching enzyme Dbr1, LaSSO not only accurately identified canonical splicing events, but also pinpointed novel, but rare, exon-skipping events, which may reflect aberrantly spliced transcripts. Compromised intron turnover perturbed gene regulation at multiple levels, including splicing and protein translation. Notably, Dbr1 function was also critical for the expression of mitochondrial genes and for the processing of self-spliced mitochondrial introns. LaSSO showed better sensitivity and accuracy than algorithms used for computational branch-point prediction or for empirical branch-point determination. Even when applied to a human data set acquired in the presence of debranching activity, LaSSO identified both canonical and exon-skipping branch points. LaSSO thus provides an effective approach for defining high-resolution maps of branch-site sequences and intronic elements on a genomic scale. LaSSO should be useful to validate introns and uncover branch-point sequences in any eukaryote, and it could be integrated into RNA-seq pipelines.
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Affiliation(s)
- Danny A Bitton
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Charalampos Rallis
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Daniel C Jeffares
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Graeme C Smith
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Yuan Y C Chen
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Sandra Codlin
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Samuel Marguerat
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
| | - Jürg Bähler
- University College London, Department of Genetics, Evolution and Environment, London WC1E 6BT, United Kingdom; University College London, UCL Cancer Institute, London WC1E 6BT, United Kingdom
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Abstract
UNLABELLED Previous studies showed that short hairpin RNA (shRNA) knockdown of the RNA lariat debranching enzyme (DBR1) led to a decrease in the production of HIV-1 cDNA. To further characterize this effect, DBR1 shRNA was introduced into GHOST-R5X4 cells, followed by infection at a multiplicity near unity with HIV-1 or an HIV-1-derived vector. DNA and RNA were isolated from whole cells and from cytoplasmic and nuclear fractions at different times postinfection. Inhibition of DBR1 had little or no effect on the formation of minus-strand strong-stop cDNA but caused a significant reduction in the formation of intermediate and full-length cDNA. Moreover, minus-strand strong-stop DNA rapidly accumulated in the cytoplasm in the first 2 h of infection but shifted to the nuclear fraction by 6 h postinfection. Regardless of DBR1 inhibition, greater than 95% of intermediate-length and full-length HIV-1 cDNA was found in the nuclear fraction at all time points. Thus, under these experimental conditions, HIV-1 cDNA synthesis was initiated in the cytoplasm and completed in the nucleus or perinuclear region of the infected cell. When nuclear import of the HIV-1 reverse transcription complex was blocked by expressing a truncated form of the mRNA cleavage and polyadenylation factor CPSF6, the completion of HIV-1 vector cDNA synthesis was detected in the cytoplasm, where it was not inhibited by DBR1 knockdown. Refinement of the cell fractionation procedure indicated that the completion of reverse transcription occurred both within nuclei and in the perinuclear region. Taken together the results indicate that in infections at a multiplicity near 1, HIV-1 reverse transcription is completed in the nucleus or perinuclear region of the infected cell, where it is dependent on DBR1. When nuclear transport is inhibited, reverse transcription is completed in the cytoplasm in a DBR1-independent manner. Thus, there are at least two mechanisms of HIV-1 reverse transcription that require different factors and occur in different intracellular locations. IMPORTANCE This study shows that HIV-1 reverse transcription starts in the cytoplasm but is completed in or on the surface of the nucleus. Moreover, we show that nuclear reverse transcription is dependent on the activity of the human RNA lariat debranchng enzyme (DBR1), while cytoplasmic reverse transcription is not. These findings may provide new avenues for inhibiting HIV-1 replication and therefore may lead to new medicines for treating HIV-1-infected individuals.
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Hesselberth JR. Lives that introns lead after splicing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2013; 4:677-91. [DOI: 10.1002/wrna.1187] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 06/14/2013] [Accepted: 06/18/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Jay R. Hesselberth
- Department of Biochemistry and Molecular Genetics; University of Colorado Anschutz Medical School; Aurora CO USA
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24
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Chen CW, Yeh MK, Shiau CY, Chiang CH, Lu DW. Efficient downregulation of VEGF in retinal pigment epithelial cells by integrin ligand-labeled liposome-mediated siRNA delivery. Int J Nanomedicine 2013; 8:2613-27. [PMID: 23901275 PMCID: PMC3726441 DOI: 10.2147/ijn.s39622] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The purpose of this study was to demonstrate the effectiveness of an integrin peptide ligand-labeled liposomal delivery system loaded with vascular endothelial growth factor (VEGF)-siRNA in a model study of gene therapy for retinopathy using human retinal pigment epithelial cells. METHODS Arg(R)-Gly(G)-Asp(D) motif peptide conjugating polyethylene glycol modified (RGD-PEGylated) liposomes were prepared using a thin-film hydration method and optimized for surface charge, particle size, small interfering RNA (siRNA) load, and entrapment efficiency. Reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assays were used to determine VEGF levels in retinal pigment epithelial cells. Cytotoxicity was determined using the 3-[4, 5-dimethylthiazol-2-yl]-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and flow cytometry. RESULTS Physicochemical properties, including particle size, zeta potential, and siRNA load, of the prepared RGD-PEGylated liposomes and their entrapment efficiency were determined to be within the following ranges: 123.8-234.1 nm, 17.31-40.09 m V, 5.27%-6.33%, and >97%, respectively. RGD-PEGylated liposome-mediated fluorescent-labeled siRNA delivery demonstrated significantly enhanced cellular uptake, and 3 mol% RGD-PEGylated liposomes (having 3β-[N-(N', N'-dimethylaminoethane) carbamoyl] cholesterol (DC-cholesterol) DSPE and DSPE-PEG(2000)-RGD with molar ratio of 50/47/3) were shown to have better efficacy with regard to specificity for retinal pigment epithelial cells, reduced cytotoxicity, and knockdown of the target molecule. CONCLUSION By integrin receptor-mediated endocytosis, 3 mol% RGD-PEGylated liposomes were shown to be a suitable vector when loaded with VEGF-siRNA for efficient downregulation of VEGF in retinal pigment epithelial cells at both the protein and gene levels. This integrin ligand-modified liposomal delivery system has therapeutic potential for ocular gene therapy.
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Affiliation(s)
| | - Ming-Kung Yeh
- Bureau of Pharmaceutical Affairs, Military of National Defense Medical Affairs Bureau
| | | | | | - Da-Wen Lu
- Department of Ophthalmology, Tri-Service General Hospital, Taipei, Taiwan
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siRNA Genome Screening Approaches to Therapeutic Drug Repositioning. Pharmaceuticals (Basel) 2013; 6:124-60. [PMID: 24275945 PMCID: PMC3816683 DOI: 10.3390/ph6020124] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 01/10/2013] [Accepted: 01/22/2013] [Indexed: 01/21/2023] Open
Abstract
Bridging high-throughput screening (HTS) with RNA interference (RNAi) has allowed for rapid discovery of the molecular basis of many diseases, and identification of potential pathways for developing safe and effective treatments. These features have identified new host gene targets for existing drugs paving the pathway for therapeutic drug repositioning. Using RNAi to discover and help validate new drug targets has also provided a means to filter and prioritize promising therapeutics. This review summarizes these approaches across a spectrum of methods and targets in the host response to pathogens. Particular attention is given to the utility of drug repurposing utilizing the promiscuous nature of some drugs that affect multiple molecules or pathways, and how these biological pathways can be targeted to regulate disease outcome.
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Kataoka N, Dobashi I, Hagiwara M, Ohno M. hDbr1 is a nucleocytoplasmic shuttling protein with a protein phosphatase-like motif essential for debranching activity. Sci Rep 2013; 3:1090. [PMID: 23346348 PMCID: PMC3549538 DOI: 10.1038/srep01090] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 12/27/2012] [Indexed: 11/09/2022] Open
Abstract
In higher eukaryotes most genes contain multiple introns. Introns are excised from pre-mRNAs by splicing and eventually degraded in the nucleus. It is likely that rapid intron turnover in the nucleus is important in higher eukaryotes, but this pathway is poorly understood. In order to gain insights into this pathway, we analyzed the human lariat RNA debranching enzyme1 (hDbr1) protein that catalyzes debranching of lariat-intron RNAs. Transfection experiments demonstrate that hDbr1 is localized in a nucleoplasm of HeLa cells through a bipartite type nuclear localization signal near carboxyl-terminus. The conserved GNHE motif, originally identified in protein phosphatase protein family, is critical for hDbr1 to dissolve lariat structure in vitro. Furthermore, heterokaryon experiments show that hDbr1 is a nucleocytoplasmic shuttling protein, suggesting novel role(s) of hDbr1 in the cytoplasm.
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Affiliation(s)
- Naoyuki Kataoka
- Medical Innovation Center, Laboratory for Malignancy Control Research, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto 606-8501, Japan.
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Armakola M, Higgins MJ, Figley MD, Barmada SJ, Scarborough EA, Diaz Z, Fang X, Shorter J, Krogan NJ, Finkbeiner S, Farese RV, Gitler AD. Inhibition of RNA lariat debranching enzyme suppresses TDP-43 toxicity in ALS disease models. Nat Genet 2012; 44:1302-9. [PMID: 23104007 PMCID: PMC3510335 DOI: 10.1038/ng.2434] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 09/10/2012] [Indexed: 12/12/2022]
Abstract
ALS is a devastating neurodegenerative disease primarily affecting motor neurons. Mutations in TDP-43 cause some forms of the disease, and cytoplasmic TDP-43 aggregates accumulate in degenerating neurons of most ALS patients. Thus, strategies aimed at targeting the toxicity of cytoplasmic TDP-43 aggregates may be effective. Here we report results from two genome-wide loss-of-function TDP-43 toxicity suppressor screens in yeast. The strongest suppressor of TDP-43 toxicity was deletion of Dbr1, which encodes RNA lariat debranching enzyme. We show that in the absence of Dbr1 enzymatic activity intronic lariats accumulate in the cytoplasm and likely act as decoys to sequester TDP-43 away from interfering with essential cellular RNAs and RNA-binding proteins. Knockdown of Dbr1 in a human neuronal cell line or in primary rodent neurons is also sufficient to rescue TDP-43 toxicity. Our findings provide insight into TDP-43 cytotoxicity and suggest decreasing Dbr1 activity could be a potential therapeutic approach for ALS.
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Affiliation(s)
- Maria Armakola
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
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Risler JK, Kenny AE, Palumbo RJ, Gamache ER, Curcio MJ. Host co-factors of the retrovirus-like transposon Ty1. Mob DNA 2012; 3:12. [PMID: 22856544 PMCID: PMC3522557 DOI: 10.1186/1759-8753-3-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/18/2012] [Indexed: 11/10/2022] Open
Abstract
UNLABELLED BACKGROUND Long-terminal repeat (LTR) retrotransposons have complex modes of mobility involving reverse transcription of their RNA genomes in cytoplasmic virus-like particles (VLPs) and integration of the cDNA copies into the host genome. The limited coding capacity of retrotransposons necessitates an extensive reliance on host co-factors; however, it has been challenging to identify co-factors that are required for endogenous retrotransposon mobility because retrotransposition is such a rare event. RESULTS To circumvent the low frequency of Ty1 LTR-retrotransposon mobility in Saccharomyces cerevisiae, we used iterative synthetic genetic array (SGA) analysis to isolate host mutations that reduce retrotransposition. Query strains that harbor a chromosomal Ty1his3AI reporter element and either the rtt101Δ or med1Δ mutation, both of which confer a hypertransposition phenotype, were mated to 4,847 haploid ORF deletion strains. Retrotransposition was measured in the double mutant progeny, and a set of 275 ORF deletions that suppress the hypertransposition phenotypes of both rtt101Δ and med1Δ were identified. The corresponding set of 275 retrotransposition host factors (RHFs) includes 45 previously identified Ty1 or Ty3 co-factors. More than half of the RHF genes have statistically robust human homologs (E < 1 x 10-10). The level of unintegrated Ty1 cDNA in 181 rhfΔ single mutants was altered <2-fold, suggesting that the corresponding co-factors stimulate retrotransposition at a step after cDNA synthesis. However, deletion of 43 RHF genes, including specific ribosomal protein and ribosome biogenesis genes and RNA degradation, modification and transport genes resulted in low Ty1 cDNA levels. The level of Ty1 Gag but not RNA was reduced in ribosome biogenesis mutants bud21Δ, hcr1Δ, loc1Δ, and puf6Δ. CONCLUSION Ty1 retrotransposition is dependent on multiple co-factors acting at different steps in the replication cycle. Human orthologs of these RHFs are potential, or in a few cases, presumptive HIV-1 co-factors in human cells. RHF genes whose absence results in decreased Ty1 cDNA include characterized RNA metabolism and modification genes, consistent with their having roles in early steps in retrotransposition such as expression, nuclear export, translation, localization, or packaging of Ty1 RNA. Our results suggest that Bud21, Hcr1, Loc1, and Puf6 promote efficient synthesis or stability of Ty1 Gag.
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Affiliation(s)
- Jenni K Risler
- Laboratory of Molecular Genetics, Wadsworth Center, Albany, NY, 12201, USA.
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29
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Cheng Z, Menees TM. RNA splicing and debranching viewed through analysis of RNA lariats. Mol Genet Genomics 2011; 286:395-410. [DOI: 10.1007/s00438-011-0635-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 06/30/2011] [Indexed: 01/24/2023]
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Chen CW, Lu DW, Yeh MK, Shiau CY, Chiang CH. Novel RGD-lipid conjugate-modified liposomes for enhancing siRNA delivery in human retinal pigment epithelial cells. Int J Nanomedicine 2011; 6:2567-80. [PMID: 22128247 PMCID: PMC3225218 DOI: 10.2147/ijn.s24447] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Human retinal pigment epithelial cells are promising target sites for small interfering RNA (siRNA) that might be used for the prevention and/or treatment of choroidal neovascularization by inhibiting the expression of angiogenic factor; for example, by downregulating expression of the vascular endothelial growth factor gene. METHODS A novel functional lipid, DSPE-PEG-RGD, a Arg(R)-Gly(G)-Asp(D) motif peptide conjugated to 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine- N-[maleimide (polyethylene glycol)-2000], was synthesized for the preparation of siRNA-loaded RGD-PEGylated liposomes to enhance uptake of encapsulated siRNA in retinal pigment epithelial cells. Various liposomes, with 1 mol% and 5 mol% PEGylated lipid or 1 mol% and 5 mol% RGD-PEGylated lipid, were fabricated. RESULTS Characterization of the liposomes, including siRNA entrapment efficiency, average particle size and ζ-potential, were determined to be as follows: >96%, 129.7 ± 51 to 230.7 ± 60.7 nm, and 17.3 ± 0.6 to 32 ± 1.3 mV, respectively. For the in vitro retinal pigment epithelial cell studies, the RGD-PEGylated liposomes had high delivery efficiency with siRNA delivery, about a four-fold increase compared with the PEGylated liposomes. Comparison of the various liposomes showed that the 1 mol% RGD-modified liposome had less cytotoxicity and higher siRNA delivery efficiency than the other liposomes. The antibody blocking assay confirmed that uptake of the 1 mol% RGD-PEGylated liposome was via integrin receptor- mediated endocytosis in retinal pigment epithelial cells. CONCLUSION The results of this study suggest that RGD-PEGylated liposomes might be useful for siRNA delivery into retinal pigment epithelial cells by integrin receptor-medicated endocytosis.
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Affiliation(s)
- Cheng-Wei Chen
- Graduate Institute of Life Sciences, National Defense Medical Center, Neihu, Taipei, Taiwan
| | - Da-Wen Lu
- Department of Ophthalmology, Tri-Service General Hospital, National Defense Medical Center, Neihu, Taipei, Taiwan
| | - Ming-Kung Yeh
- Institution of Preventive Medicine, National Defense Medical Center, Neihu, Taipei, Taiwan
| | - Chia-Yang Shiau
- Graduate Institute of Medical Sciences, National Defense Medical Center, Neihu, Taipei, Taiwan
| | - Chiao-Hsi Chiang
- Graduate Institute of Life Sciences, National Defense Medical Center, Neihu, Taipei, Taiwan
- School of Pharmacy, National Defense Medical Center, Neihu, Taipei, Taiwan
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Abstract
Long terminal repeat (LTR) retrotransposons are not only the ancient predecessors of retroviruses, but they constitute significant fractions of the genomes of many eukaryotic species. Studies of their structure and function are motivated by opportunities to gain insight into common functions of retroviruses and retrotransposons, diverse mechanisms of intracellular genomic mobility, and host factors that diminish or enhance retrotransposition. This review focuses on the nucleocapsid (NC) protein of a Saccharomyces cerevisiae LTR retrotransposon, the metavirus, Ty3. Retrovirus NC promotes genomic (g)RNA dimerization and packaging, tRNA primer annealing, reverse transcription strand transfers, and host protein interactions with gRNA. Studies of Ty3 NC have revealed key roles for Ty3 NC in formation of retroelement assembly sites (retrosomes), and in chaperoning primer tRNA to both dimerize and circularize Ty3 gRNA. We speculate that Ty3 NC, together with P-body and stress-granule proteins, plays a role in transitioning Ty3 RNA from translation template to gRNA, and that interactions between the acidic spacer domain of Ty3 Gag3 and the adjacent basic NC domain control condensation of the virus-like particle.
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Affiliation(s)
- Suzanne B Sandmeyer
- Department of Biological Chemistry, School of Medicine, University of California, Irvine, CA USA.
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Warrilow D, Warren K, Harrich D. Strand transfer and elongation of HIV-1 reverse transcription is facilitated by cell factors in vitro. PLoS One 2010; 5:e13229. [PMID: 20949087 PMCID: PMC2950853 DOI: 10.1371/journal.pone.0013229] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Accepted: 09/16/2010] [Indexed: 11/19/2022] Open
Abstract
Recent work suggests a role for multiple host factors in facilitating HIV-1 reverse transcription. Previously, we identified a cellular activity which increases the efficiency of HIV-1 reverse transcription in vitro. Here, we describe aspects of the activity which shed light on its function. The cellular factor did not affect synthesis of strong-stop DNA but did improve downstream DNA synthesis. The stimulatory activity was isolated by gel filtration in a single fraction of the exclusion volume. Velocity-gradient purified HIV-1, which was free of detectable RNase activity, showed poor reverse transcription efficiency but was strongly stimulated by partially purified cell proteins. Hence, the cell factor(s) did not inactivate an RNase activity that might degrade the viral genomic RNA and block completion of reverse transcription. Instead, the cell factor(s) enhanced first strand transfer and synthesis of late reverse transcription suggesting it stabilized the reverse transcription complex. The factor did not affect lysis of HIV-1 by Triton X-100 in the endogenous reverse transcription (ERT) system, and ERT reactions with HIV-1 containing capsid mutations, which varied the biochemical stability of viral core structures and impeded reverse transcription in cells, showed no difference in the ability to be stimulated by the cell factor(s) suggesting a lack of involvement of the capsid in the in vitro assay. In addition, reverse transcription products were found to be resistant to exogenous DNase I activity when the active fraction was present in the ERT assay. These results indicate that the cell factor(s) may improve reverse transcription by facilitating DNA strand transfer and DNA synthesis. It also had a protective function for the reverse transcription products, but it is unclear if this is related to improved DNA synthesis.
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Affiliation(s)
- David Warrilow
- Division of Immunology and Infectious Disease, Queensland Institute of Medical Research, Brisbane, Australia
- Griffith Medical Research College, A Joint Program of Griffith University and the Queensland Institute of Medical Research, Herston, Australia
| | - Kylie Warren
- Division of Immunology and Infectious Disease, Queensland Institute of Medical Research, Brisbane, Australia
- School of Natural Sciences, University of Western Sydney, Hawkesbury, Australia
| | - David Harrich
- Division of Immunology and Infectious Disease, Queensland Institute of Medical Research, Brisbane, Australia
- Griffith Medical Research College, A Joint Program of Griffith University and the Queensland Institute of Medical Research, Herston, Australia
- * E-mail: .
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Inhibition of HIV-1 replication by small interfering RNAs directed against glioma pathogenesis related protein (GliPR) expression. Retrovirology 2010; 7:26. [PMID: 20356381 PMCID: PMC2859388 DOI: 10.1186/1742-4690-7-26] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Accepted: 03/31/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Previously, we showed that glioma pathogenesis related protein (GliPR) is induced in CEM T cells upon HIV-1 infection in vitro. To examine whether GliPR plays a role as HIV dependency factor (HDF), we tested the effect of GliPR suppression by siRNA on HIV-1 replication. RESULTS Induction of GliPR expression by HIV-1 was confirmed in P4-CCR5 cells. When GliPR was suppressed by siRNA, HIV-1 replication was significantly reduced as measured by HIV-1 transcript levels, HIV-1 p24 protein levels, and HIV-1 LTR-driven reporter gene expression, suggesting that GliPR is a cellular co-factor of HIV-1. Microarray analysis of uninfected HeLa cells following knockdown of GliPR revealed, among a multitude of gene expression alterations, a down-regulation of syndecan-1, syndecan-2, protein kinase C alpha (PRKCA), the catalytic subunit beta of cAMP-dependent protein kinase (PRKACB), nuclear receptor co-activator 3 (NCOA3), and cell surface protein CD59 (protectin), all genes having relevance for HIV-1 pathology. CONCLUSIONS The up-regulation of GliPR by HIV-1 and the early significant inhibition of HIV-1 replication mediated by knockdown of GliPR reveal GliPR as an important HIV-1 dependency factor (HDF), which may be exploited for HIV-1 inhibition.
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Zaree Mahmodabady A, Javadi HR, Kamali M, Najafi A, Hojati Z. Bcr-abl silencing by specific small-interference RNA expression vector as a potential treatment for chronic myeloid leukemia. IRANIAN BIOMEDICAL JOURNAL 2010; 14:1-8. [PMID: 20683492 PMCID: PMC3878140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 10/10/2009] [Revised: 03/06/2010] [Accepted: 01/11/2010] [Indexed: 05/29/2023]
Abstract
BACKGROUND RNA interference (RNAi) is the mechanism of gene silencing-mediated messenger RNA degradation by small interference RNA (siRNA), which becomes a powerful tool for in vivo research, especially in the areas of cancer. In this research, the potential use of an expression vector as a specific siRNA producing tool for silencing of Bcr-abl in K562 cell line has been investigated. METHODS siRNA specific for Bcr-abl as short hairpin RNA (shRNA) was designed and cloned in expression vector (pRNAH1.1/Neo). K562 cells were cultured in RPMI media and transfected with shRNA expressing vector using lipofectamin 2000. Successful transfection was confirmed by significant increase of enhanced green fluorescent protein (EGFP) levels in K562-treated cells with expression vector (pEGFP-C1). In vitro studies in human K562 cell line entailed modulation of endogenous Bcr-abl mRNA levels which induced apoptosis. Effects of siRNA treatment on K562 cells were measured by ELISA. RESULTS Successful expression of siRNA was confirmed by significant reduction of Bcr-abl mRNA levels in K562 cells treated with expression vector (pRNAH1.1/Neo). siRNA directed against Bcr-abl effectively induced apoptosis and reduced viability in human K562 cell lines. CONCLUSION Expression vector of siRNA can be used in vitro to target specific RNA and to reduce the levels of the specific gene product in the targeted cells. Results of this work suggest that RNAi has potential application for the treatment of a variety of diseases, including those involving abnormal gene expression and viral contamination.
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MESH Headings
- Apoptosis/physiology
- Cell Survival/physiology
- Fusion Proteins, bcr-abl/genetics
- Gene Expression Regulation, Leukemic
- Genetic Therapy/methods
- Humans
- K562 Cells
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/therapy
- RNA, Messenger/metabolism
- RNA, Small Interfering/genetics
- Transfection
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Affiliation(s)
- Ali Zaree Mahmodabady
- Dept. of Biochemistry, Medical Faculty, Molecular Biology Research Center and Chemical Injuries Research Center, Baqiyatallah University, Tehran;
| | - Hamid Reza Javadi
- Dept. of Biochemistry, Medical Faculty, Baqiyatallah University, Tehran;
| | - Mehdi Kamali
- Nanobiotechnology Research Center, Baqiyatallah University, Tehran;
| | - Ali Najafi
- Molecular Biology Research Center, Baqiyatallah University, Tehran, Iran
| | - Zahra Hojati
- Dept. of Biochemistry, Medical Faculty, Baqiyatallah University, Tehran;
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Abstract
We have analyzed host cell genes linked to HIV replication that were identified in nine genome-wide studies, including three independent siRNA screens. Overlaps among the siRNA screens were very modest (<7% for any pairwise combination), and similarly, only modest overlaps were seen in pairwise comparisons with other types of genome-wide studies. Combining all genes from the genome-wide studies together with genes reported in the literature to affect HIV yields 2,410 protein-coding genes, or fully 9.5% of all human genes (though of course some of these are false positive calls). Here we report an “encyclopedia” of all overlaps between studies (available at http://www.hostpathogen.org), which yielded a more extensively corroborated set of host factors assisting HIV replication. We used these genes to calculate refined networks that specify cellular subsystems recruited by HIV to assist in replication, and present additional analysis specifying host cell genes that are attractive as potential therapeutic targets.
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36
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Beauregard A, Curcio MJ, Belfort M. The take and give between retrotransposable elements and their hosts. Annu Rev Genet 2009; 42:587-617. [PMID: 18680436 DOI: 10.1146/annurev.genet.42.110807.091549] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Retrotransposons mobilize via RNA intermediates and usually carry with them the agent of their mobility, reverse transcriptase. Retrotransposons are streamlined, and therefore rely on host factors to proliferate. However, retrotransposons are exposed to cellular forces that block their paths. For this review, we have selected for our focus elements from among target-primed (TP) retrotransposons, also called non-LTR retrotransposons, and extrachromosomally-primed (EP) retrotransposons, also called LTR retrotransposons. The TP retrotransposons considered here are group II introns, LINEs and SINEs, whereas the EP elements considered are the Ty and Tf retrotransposons, with a brief comparison to retroviruses. Recurring themes for these elements, in hosts ranging from bacteria to humans, are tie-ins of the retrotransposons to RNA metabolism, DNA replication and repair, and cellular stress. Likewise, there are parallels among host-cell defenses to combat rampant retrotransposon spread. The interactions between the retrotransposon and the host, and their coevolution to balance the tension between retrotransposon proliferation and host survival, form the basis of this review.
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Affiliation(s)
- Arthur Beauregard
- New York State Department of Health, Center for Medical Sciences, Albany, New York 12208, 12201-2002, USA.
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37
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Singh SK. RNA interference and its therapeutic potential against HIV infection. Expert Opin Biol Ther 2008; 8:449-61. [PMID: 18352849 DOI: 10.1517/14712598.8.4.449] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND HIV-1 infection is the major cause of AIDS. RNA interference (RNAi) has great potential to work as a powerful tool against HIV infection. Therefore, the possibilities of use of siRNA (small-interfering RNA) as a tool to deal with HIV infection are discussed in this article. OBJECTIVE Highly active anti retroviral therapy (HAART) has been successful in reducing the rate of progression to AIDS, but HIV utilizes various tricks to escape from the inhibitory effect of HAART. Therefore, new tools are required to delay progression of infection or block the replication cycle of HIV. METHODS This article has been written on the basis of informations available in the form of published literature in various journals. CONCLUSION RNAi is a very promising strategy that in principle will provide many new targets against HIV infection. The mechanism of sequence complementarity utilized by siRNAs against their targets provides a new approach to fight against HIV infection. However, this technology still needs many fine refinements before its potential for HIV treatment strategies can be utilized. This review discusses the possibilities of using siRNA as a therapeutic tool for HIV treatment.
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Affiliation(s)
- Sunit K Singh
- Centre for Cellular and Molecular Biology, Section of Infectious Diseases & Immunobiology, Room No: S107, South Wing (Ground Floor), Uppal Road, Hyderabad-500007, AP, India.
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Barichievy S, Saayman S, von Eije KJ, Morris KV, Arbuthnot P, Weinberg MS. The inhibitory efficacy of RNA POL III-expressed long hairpin RNAs targeted to untranslated regions of the HIV-1 5' long terminal repeat. Oligonucleotides 2008; 17:419-31. [PMID: 17896874 DOI: 10.1089/oli.2007.0095] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) is a lentivirus that causes persistent infection resulting in the demise of immune regulatory cells, and ensuing diseases associated with acquired immune deficiency syndrome (AIDS). Although current therapeutic modalities have had a significant impact on mortality rates, novel therapies are constantly needed to prevent the emergence of resistant viral variants that escape the effects of antivirals. RNA Interference (RNAi) is a promising therapeutic modality for the inhibition of HIV-1 RNAs. Traditionally, RNAi effector sequences include expressed short hairpin RNAs (shRNAs) or short interfering RNAs (siRNAs). Recently, expressed long hairpin RNAs (lhRNAs) have been used with the aim of generating multiple independent siRNAs, which simultaneously target different susceptible sites on HIV-1. Here, modified lhRNAs expressed from U6 RNA Pol III promoters were targeted to sites within the first transcribed sequences of the HIV-1 5' long terminal repeat (LTR) region. Both Tat-dependent and independent suppressive efficacy was demonstrated against subtype B and C reporter sequences; however, lhRNAs complementary to the TAR stem-loop were refractory to silencing. None of the lhRNAs induced an unwanted interferon response as measured by interferon beta levels. Silencing by the lhRNAs was not equal across the extent of its cognate sequence, with the greatest efficacy observed for sequences located at the base of the stem. Nevertheless, direct antireplicative activity was seen when targeting lhRNAs to a subtype B HIV clone pNL4-3 Luc and a subtype C wild-type HIV-1 strain, FV5. These data highlight distinct target loci within the 5' LTR of HIV-1 that are susceptible to lhRNA targeting, and may prove to have an important advantage over other RNAi target sites within HIV-1. Although lhRNAs themselves require further manipulation to improve their overall efficacy in generating multiple functioning siRNAs, they may prove useful in any combinatorial-based approach to treating HIV-1 infection.
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Affiliation(s)
- Samantha Barichievy
- Antiviral Gene Therapy Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
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Zhang J, Wu YO, Xiao L, Li K, Chen LL, Sirois P. Therapeutic potential of RNA interference against cellular targets of HIV infection. Mol Biotechnol 2007; 37:225-36. [PMID: 17952669 PMCID: PMC7091338 DOI: 10.1007/s12033-007-9000-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 08/09/2007] [Indexed: 12/11/2022]
Abstract
RNA interference is not only very promising in identifying new targets for drug development, siRNA/shRNA themselves may be directly used as therapeutic agents. In inhibiting viral infections by RNA interference, both viral targets and cellular proteins have been evaluated. Most of the early studies in this field had chosen viral targets for RNA interference. However, recent efforts are mainly focusing on cellular proteins for RNA silencing due to the realization that a variety of viral responses substantially minimize siRNA effects. With the application of siRNA approaching, many new cellular targets relevant to HIV infection have been identified. The value of siRNA/shRNA in the treatment of AIDS is largely dependent on better understanding of the biology of HIV replication. Efforts in the identification of cellular processes with the employment of siRNA/shRNA have shed some new lights on our understanding of how HIV infection occurs. Furthermore, the relative specific effects and simplicity of design makes siRNA/shRNA themselves to be favorable drug leads.
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Affiliation(s)
- Jia Zhang
- Gene Core, The Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
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40
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Menees TM, Müller B, Kräusslich HG. The major 5' end of HIV type 1 RNA corresponds to G456. AIDS Res Hum Retroviruses 2007; 23:1042-8. [PMID: 17725422 DOI: 10.1089/aid.2006.0275] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In the course of studies on HIV-1 RNA structure, we determined that the main 5' end of viral RNA from virions and virus producer cells corresponds to G456 in the proviral DNA sequence, one or two nucleotides down-stream from the reported ends that correspond to G454 and G455. We mapped 5' ends using the highly accurate RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE) method. The reactivity of the 5' ends indicates that they are mainly capped, although the presence of some uncapped (5'-triphosphorylated) RNA cannot formally be excluded. When we used a 5' mapping method susceptible to incorporating a cytosine at the 3' end of cDNA first strands, at a position templated by the 7-methylguanosine cap, 50% of clones derived from virion RNA had incorporated the additional cytosine. Reassignment of the 5' end has consequences for the design of short RNAs used to study HIV-1 RNA structural dynamics.
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Affiliation(s)
- Thomas M Menees
- School of Biological Sciences, Division of Cell Bilogy and Biophysics, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA.
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41
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Maxwell PH, Curcio MJ. Host factors that control long terminal repeat retrotransposons in Saccharomyces cerevisiae: implications for regulation of mammalian retroviruses. EUKARYOTIC CELL 2007; 6:1069-80. [PMID: 17496126 PMCID: PMC1951103 DOI: 10.1128/ec.00092-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Patrick H Maxwell
- Center for Medical Sciences, Wadsworth Center, PO Box 2002, Albany, NY 12201-2002, USA
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Zhang Z, Hesselberth JR, Fields S. Genome-wide identification of spliced introns using a tiling microarray. Genome Res 2007; 17:503-9. [PMID: 17351133 PMCID: PMC1832097 DOI: 10.1101/gr.6049107] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The prediction of gene models from genome sequence remains an unsolved problem. One hallmark of eukaryotic gene structure is the presence of introns, which are spliced out of pre-mRNAs prior to translation. The excised introns are released in the form of lariats, which must be debranched prior to their turnover. In the yeast Saccharomyces cerevisiae, the absence of the debranching enzyme causes these lariat RNAs to accumulate. This accumulation allows a comparison of tiling array signals of RNA from the debranching mutant to the wild-type parent strain, and thus the identification of lariats on a genome-wide scale. This approach identified 141 of 272 known introns, confirmed three previously predicted introns, predicted four novel introns (of which two were experimentally confirmed), and led to the reannotation of four others. In many instances, signals from the tiling array delineated the 5' splice site and branchpoint site, confirming predicted gene structures. Nearly all introns that went undetected are present in mRNAs expressed at low levels. Overall, 97% of the significant probes could be attributed either to spliced introns or to genes up-regulated by deletion of the debranching enzyme. Because the debranching enzyme is conserved among eukaryotes, this approach could be generally applicable for the annotation of eukaryotic genes and the detection of novel and alternative splice forms.
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Affiliation(s)
- Zhihong Zhang
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington 98195, USA
| | - Jay R. Hesselberth
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington 98195, USA
| | - Stanley Fields
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington 98195, USA
- Corresponding author.E-mail ; fax (206) 543-0754
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