51
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Chen MC, Murat P, Abecassis K, Ferré-D'Amaré AR, Balasubramanian S. Insights into the mechanism of a G-quadruplex-unwinding DEAH-box helicase. Nucleic Acids Res 2015; 43:2223-31. [PMID: 25653156 PMCID: PMC4344499 DOI: 10.1093/nar/gkv051] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The unwinding of nucleic acid secondary structures within cells is crucial to maintain genomic integrity and prevent abortive transcription and translation initiation. DHX36, also known as RHAU or G4R1, is a DEAH-box ATP-dependent helicase highly specific for DNA and RNA G-quadruplexes (G4s). A fundamental mechanistic understanding of the interaction between helicases and their G4 substrates is important to elucidate G4 biology and pave the way toward G4-targeted therapies. Here we analyze how the thermodynamic stability of G4 substrates affects binding and unwinding by DHX36. We modulated the stability of the G4 substrates by varying the sequence and the number of G-tetrads and by using small, G4-stabilizing molecules. We found an inverse correlation between the thermodynamic stability of the G4 substrates and rates of unwinding by DHX36. In stark contrast, the ATPase activity of the helicase was largely independent of substrate stability pointing toward a decoupling mechanism akin to what has been observed for many double-stranded DEAD-box RNA helicases. Our study provides the first evidence that DHX36 uses a local, non-processive mechanism to unwind G4 substrates, reminiscent of that of eukaryotic initiation factor 4A (eIF4A) on double-stranded substrates.
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Affiliation(s)
- Michael C Chen
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK National Heart, Lung and Blood Institute, 50 South Drive, MSC-8012, Bethesda, MD 20892-8012, USA
| | - Pierre Murat
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Keren Abecassis
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Adrian R Ferré-D'Amaré
- National Heart, Lung and Blood Institute, 50 South Drive, MSC-8012, Bethesda, MD 20892-8012, USA
| | - Shankar Balasubramanian
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Cambridge, UK
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52
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Duan XL, Liu NN, Yang YT, Li HH, Li M, Dou SX, Xi XG. G-quadruplexes significantly stimulate Pif1 helicase-catalyzed duplex DNA unwinding. J Biol Chem 2015; 290:7722-35. [PMID: 25627683 DOI: 10.1074/jbc.m114.628008] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The evolutionarily conserved G-quadruplexes (G4s) are faithfully inherited and serve a variety of cellular functions such as telomere maintenance, gene regulation, DNA replication initiation, and epigenetic regulation. Different from the Watson-Crick base-pairing found in duplex DNA, G4s are formed via Hoogsteen base pairing and are very stable and compact DNA structures. Failure of untangling them in the cell impedes DNA-based transactions and leads to genome instability. Cells have evolved highly specific helicases to resolve G4 structures. We used a recombinant nuclear form of Saccharomyces cerevisiae Pif1 to characterize Pif1-mediated DNA unwinding with a substrate mimicking an ongoing lagging strand synthesis stalled by G4s, which resembles a replication origin and a G4-structured flap in Okazaki fragment maturation. We find that the presence of G4 may greatly stimulate the Pif1 helicase to unwind duplex DNA. Further studies reveal that this stimulation results from G4-enhanced Pif1 dimerization, which is required for duplex DNA unwinding. This finding provides new insights into the properties and functions of G4s. We discuss the observed activation phenomenon in relation to the possible regulatory role of G4s in the rapid rescue of the stalled lagging strand synthesis by helping the replicator recognize and activate the replication origin as well as by quickly removing the G4-structured flap during Okazaki fragment maturation.
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Affiliation(s)
- Xiao-Lei Duan
- From the College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Na-Nv Liu
- From the College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Yan-Tao Yang
- From the College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Hai-Hong Li
- From the College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Ming Li
- the CAS Key Laboratory of Soft Matter Physics, International Associated Laboratory of CNRS-Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China, and
| | - Shuo-Xing Dou
- the CAS Key Laboratory of Soft Matter Physics, International Associated Laboratory of CNRS-Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China, and
| | - Xu-Guang Xi
- From the College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China, the Laboratoire de Biologie et Pharmacologie Appliquée, Ecole Normale Supérieure de Cachan, CNRS, 61 Avenue du Président Wilson, 94235 Cachan, France
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53
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A G-quadruplex DNA structure resolvase, RHAU, is essential for spermatogonia differentiation. Cell Death Dis 2015; 6:e1610. [PMID: 25611385 PMCID: PMC4669769 DOI: 10.1038/cddis.2014.571] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 11/17/2014] [Accepted: 11/20/2014] [Indexed: 01/02/2023]
Abstract
G-quadruplex (G4) DNA and G4 DNA resolvase are involved in a variety of biological processes. To understand the biological function of G4 DNA structures and their resolvases in spermatogenesis, we investigated the distribution of G4 structures in mouse testis and identified their alterations during spermatogenesis. Meanwhile, we studied the function of RNA helicase associated with AU-rich element (RHAU), a G4 DNA resolvase, in spermatogenesis with a germ-cell-specific knockout mouse model. The results showed that the ablation of RHAU in germ cells caused the increase of G4 structures and thus resulted in the decrease of spermatogonial differentiation. c-kit, a spermatogonia differentiation-related gene, contains two G4 DNA motifs on its promoter. We found its expression was significantly downregulated in RHAU conditional knockout testis. A further analysis demonstrated that RHAU directly bound to the G4 structures to activate c-kit expression. We concluded that RHAU regulates spermatogonia differentiation by promoting c-kit expression via directly binding to the G4 DNA motifs c-kit promoter.
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54
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Byrd AK, Raney KD. A parallel quadruplex DNA is bound tightly but unfolded slowly by pif1 helicase. J Biol Chem 2015; 290:6482-94. [PMID: 25589786 DOI: 10.1074/jbc.m114.630749] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
DNA sequences that can form intramolecular quadruplex structures are found in promoters of proto-oncogenes. Many of these sequences readily fold into parallel quadruplexes. Here we characterize the ability of yeast Pif1 to bind and unfold a parallel quadruplex DNA substrate. We found that Pif1 binds more tightly to the parallel quadruplex DNA than single-stranded DNA or tailed duplexes. However, Pif1 unwinding of duplexes occurs at a much faster rate than unfolding of a parallel intramolecular quadruplex. Pif1 readily unfolds a parallel quadruplex DNA substrate in a multiturnover reaction and also generates some product under single cycle conditions. The rate of ATP hydrolysis by Pif1 is reduced when bound to a parallel quadruplex compared with single-stranded DNA. ATP hydrolysis occurs at a faster rate than quadruplex unfolding, indicating that some ATP hydrolysis events are non-productive during unfolding of intramolecular parallel quadruplex DNA. However, product eventually accumulates at a slow rate.
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Affiliation(s)
- Alicia K Byrd
- From the Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Kevin D Raney
- From the Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
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55
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Biochemical characterization of G4 quadruplex telomerase RNA unwinding by the RNA helicase RHAU. Methods Mol Biol 2015; 1259:125-35. [PMID: 25579584 DOI: 10.1007/978-1-4939-2214-7_9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
G4 quadruplexes are stable secondary structures prevalent in DNA and RNA that exhibit diverse regulatory functions. Herein, we describe an in vitro technique using the purified RNA helicase RHAU to unwind a G4 quadruplex identified near the 5' end of the human telomerase RNA (hTR). A synthetic RNA corresponding to the quadruplex forming region of hTR (hTR10-43), as well as a predicted complementary strand (25P1), are combined in a reaction containing the purified helicase and ATP. Reaction products and appropriate controls are resolved by native gel electrophoresis. Gels can be stained using a combination of total RNA and quadruplex-specific dyes to observe the expected quadruplex to duplex conversion. This straightforward method can be extended to study structural changes in other inter- or intramolecular quadruplex containing DNA/RNA molecules with the RHAU helicase or other RNA/DNA remodeling enzymes.
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56
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Wang Q, Han G, Ye J, Gao X, Niu H, Zhao J, Chai Y, Li N, Yin H. Characterization of the polycystic kidney disease 2 gene promoter. Genomics 2014; 104:512-9. [DOI: 10.1016/j.ygeno.2014.08.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 08/13/2014] [Accepted: 08/15/2014] [Indexed: 12/25/2022]
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57
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DNA and RNA quadruplex-binding proteins. Int J Mol Sci 2014; 15:17493-517. [PMID: 25268620 PMCID: PMC4227175 DOI: 10.3390/ijms151017493] [Citation(s) in RCA: 191] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 09/15/2014] [Accepted: 09/22/2014] [Indexed: 02/01/2023] Open
Abstract
Four-stranded DNA structures were structurally characterized in vitro by NMR, X-ray and Circular Dichroism spectroscopy in detail. Among the different types of quadruplexes (i-Motifs, minor groove quadruplexes, G-quadruplexes, etc.), the best described are G-quadruplexes which are featured by Hoogsteen base-paring. Sequences with the potential to form quadruplexes are widely present in genome of all organisms. They are found often in repetitive sequences such as telomeric ones, and also in promoter regions and 5' non-coding sequences. Recently, many proteins with binding affinity to G-quadruplexes have been identified. One of the initially portrayed G-rich regions, the human telomeric sequence (TTAGGG)n, is recognized by many proteins which can modulate telomerase activity. Sequences with the potential to form G-quadruplexes are often located in promoter regions of various oncogenes. The NHE III1 region of the c-MYC promoter has been shown to interact with nucleolin protein as well as other G-quadruplex-binding proteins. A number of G-rich sequences are also present in promoter region of estrogen receptor alpha. In addition to DNA quadruplexes, RNA quadruplexes, which are critical in translational regulation, have also been predicted and observed. For example, the RNA quadruplex formation in telomere-repeat-containing RNA is involved in interaction with TRF2 (telomere repeat binding factor 2) and plays key role in telomere regulation. All these fundamental examples suggest the importance of quadruplex structures in cell processes and their understanding may provide better insight into aging and disease development.
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58
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A targeted oligonucleotide enhancer of SMN2 exon 7 splicing forms competing quadruplex and protein complexes in functional conditions. Cell Rep 2014; 9:193-205. [PMID: 25263560 PMCID: PMC4536295 DOI: 10.1016/j.celrep.2014.08.051] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/17/2014] [Accepted: 08/21/2014] [Indexed: 01/20/2023] Open
Abstract
The use of oligonucleotides to activate the splicing of selected exons is limited by a poor understanding of the mechanisms affected. A targeted bifunctional oligonucleotide enhancer of splicing (TOES) anneals to SMN2 exon 7 and carries an exonic splicing enhancer (ESE) sequence. We show that it stimulates splicing specifically of intron 6 in the presence of repressing sequences in intron 7. Complementarity to the 5' end of exon 7 increases U2AF65 binding, but the ESE sequence is required for efficient recruitment of U2 snRNP. The ESE forms at least three coexisting discrete states: a quadruplex, a complex containing only hnRNP F/H, and a complex enriched in the activator SRSF1. Neither hnRNP H nor quadruplex formation contributes to ESE activity. The results suggest that splicing limited by weak signals can be rescued by rapid exchange of TOES oligonucleotides in various complexes and raise the possibility that SR proteins associate transiently with ESEs.
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59
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Bharti SK, Sommers JA, Zhou J, Kaplan DL, Spelbrink JN, Mergny JL, Brosh RM. DNA sequences proximal to human mitochondrial DNA deletion breakpoints prevalent in human disease form G-quadruplexes, a class of DNA structures inefficiently unwound by the mitochondrial replicative Twinkle helicase. J Biol Chem 2014; 289:29975-93. [PMID: 25193669 DOI: 10.1074/jbc.m114.567073] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial DNA deletions are prominent in human genetic disorders, cancer, and aging. It is thought that stalling of the mitochondrial replication machinery during DNA synthesis is a prominent source of mitochondrial genome instability; however, the precise molecular determinants of defective mitochondrial replication are not well understood. In this work, we performed a computational analysis of the human mitochondrial genome using the "Pattern Finder" G-quadruplex (G4) predictor algorithm to assess whether G4-forming sequences reside in close proximity (within 20 base pairs) to known mitochondrial DNA deletion breakpoints. We then used this information to map G4P sequences with deletions characteristic of representative mitochondrial genetic disorders and also those identified in various cancers and aging. Circular dichroism and UV spectral analysis demonstrated that mitochondrial G-rich sequences near deletion breakpoints prevalent in human disease form G-quadruplex DNA structures. A biochemical analysis of purified recombinant human Twinkle protein (gene product of c10orf2) showed that the mitochondrial replicative helicase inefficiently unwinds well characterized intermolecular and intramolecular G-quadruplex DNA substrates, as well as a unimolecular G4 substrate derived from a mitochondrial sequence that nests a deletion breakpoint described in human renal cell carcinoma. Although G4 has been implicated in the initiation of mitochondrial DNA replication, our current findings suggest that mitochondrial G-quadruplexes are also likely to be a source of instability for the mitochondrial genome by perturbing the normal progression of the mitochondrial replication machinery, including DNA unwinding by Twinkle helicase.
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Affiliation(s)
- Sanjay Kumar Bharti
- From the Laboratory of Molecular Gerontology, NIA, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224
| | - Joshua A Sommers
- From the Laboratory of Molecular Gerontology, NIA, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224
| | - Jun Zhou
- the ARNA Laboratory, University of Bordeaux, F-33000 Bordeaux, France, INSERM U869, Institut Européen de Chimie et Biologie (IECB), F-33600 Pessac, France
| | - Daniel L Kaplan
- the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32312
| | - Johannes N Spelbrink
- the FinMIT Centre of Excellence, BioMediTech and Tampere University Hospital, Pirkanmaa Hospital District, University of Tampere, FI-33014 Tampere, Finland, and the Department of Pediatrics, Nijmegan Centre for Mitochondrial Disorders, Radboud University Medical Centre, Geert Grooteplein 10, P. O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Jean-Louis Mergny
- the ARNA Laboratory, University of Bordeaux, F-33000 Bordeaux, France, INSERM U869, Institut Européen de Chimie et Biologie (IECB), F-33600 Pessac, France
| | - Robert M Brosh
- From the Laboratory of Molecular Gerontology, NIA, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224,
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60
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Müller S, Rodriguez R. G-quadruplex interacting small molecules and drugs: from bench toward bedside. Expert Rev Clin Pharmacol 2014; 7:663-79. [DOI: 10.1586/17512433.2014.945909] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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61
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Tippana R, Xiao W, Myong S. G-quadruplex conformation and dynamics are determined by loop length and sequence. Nucleic Acids Res 2014; 42:8106-14. [PMID: 24920827 PMCID: PMC4081081 DOI: 10.1093/nar/gku464] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The quadruplex forming G-rich sequences are unevenly distributed throughout the human genome. Their enrichment in oncogenic promoters and telomeres has generated interest in targeting G-quadruplex (GQ) for an anticancer therapy. Here, we present a quantitative analysis on the conformations and dynamics of GQ forming sequences measured by single molecule fluorescence. Additionally, we relate these properties to GQ targeting ligands and G4 resolvase 1 (G4R1) protein binding. Our result shows that both the loop (non-G components) length and sequence contribute to the conformation of the GQ. Real time single molecule traces reveal that the folding dynamics also depend on the loop composition. We demonstrate that GQ-stabilizing small molecules, N-methyl mesoporphyrin IX (NMM), its analog, NMP and the G4R1 protein bind selectively to the parallel GQ conformation. Our findings point to the complexity of GQ folding governed by the loop length and sequence and how the GQ conformation determines the small molecule and protein binding propensity.
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Affiliation(s)
- Ramreddy Tippana
- Bioengineering Department, University of Illinois, 1304 W. Springfield Ave., Urbana, IL 61801, USA
| | - Weikun Xiao
- Bioengineering Department, University of Illinois, 1304 W. Springfield Ave., Urbana, IL 61801, USA
| | - Sua Myong
- Bioengineering Department, University of Illinois, 1304 W. Springfield Ave., Urbana, IL 61801, USA Biophysics and Computational Biology, 1110 W. Green St., Urbana, IL 61801, USA Institute for Genomic Biology, 1206 Gregory Drive, Urbana, IL 61801, USA Physics Frontier Center (Center of Physics for Living Cells), University of Illinois, 1110 W. Green St., Urbana, IL 61801, USA
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62
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Yoo JS, Takahasi K, Ng CS, Ouda R, Onomoto K, Yoneyama M, Lai JC, Lattmann S, Nagamine Y, Matsui T, Iwabuchi K, Kato H, Fujita T. DHX36 enhances RIG-I signaling by facilitating PKR-mediated antiviral stress granule formation. PLoS Pathog 2014; 10:e1004012. [PMID: 24651521 PMCID: PMC3961341 DOI: 10.1371/journal.ppat.1004012] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 02/04/2014] [Indexed: 12/14/2022] Open
Abstract
RIG-I is a DExD/H-box RNA helicase and functions as a critical cytoplasmic sensor for RNA viruses to initiate antiviral interferon (IFN) responses. Here we demonstrate that another DExD/H-box RNA helicase DHX36 is a key molecule for RIG-I signaling by regulating double-stranded RNA (dsRNA)-dependent protein kinase (PKR) activation, which has been shown to be essential for the formation of antiviral stress granule (avSG). We found that DHX36 and PKR form a complex in a dsRNA-dependent manner. By forming this complex, DHX36 facilitates dsRNA binding and phosphorylation of PKR through its ATPase/helicase activity. Using DHX36 KO-inducible MEF cells, we demonstrated that DHX36 deficient cells showed defect in IFN production and higher susceptibility in RNA virus infection, indicating the physiological importance of this complex in host defense. In summary, we identify a novel function of DHX36 as a critical regulator of PKR-dependent avSG to facilitate viral RNA recognition by RIG-I-like receptor (RLR).
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Affiliation(s)
- Ji-Seung Yoo
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kiyohiro Takahasi
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Institute for Innovative NanoBio Drug Discovery and Development, Graduate School of Pharmaceutical Science, Kyoto University, Kyoto, Japan
| | - Chen Seng Ng
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Ryota Ouda
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Koji Onomoto
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chuo-ku, Chiba, Japan
| | - Mitsutoshi Yoneyama
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chuo-ku, Chiba, Japan
| | - Janice Ching Lai
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Simon Lattmann
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Yoshikuni Nagamine
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Tadashi Matsui
- Department of Biochemistry I, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, Japan
| | - Kuniyoshi Iwabuchi
- Department of Biochemistry I, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, Japan
| | - Hiroki Kato
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Takashi Fujita
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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63
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Booy EP, Howard R, Marushchak O, Ariyo EO, Meier M, Novakowski SK, Deo SR, Dzananovic E, Stetefeld J, McKenna SA. The RNA helicase RHAU (DHX36) suppresses expression of the transcription factor PITX1. Nucleic Acids Res 2013; 42:3346-61. [PMID: 24369427 PMCID: PMC3950718 DOI: 10.1093/nar/gkt1340] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
RNA Helicase associated with AU-rich element (RHAU) (DHX36) is a DEAH (Aspartic acid, Glumatic Acid, Alanine, Histidine)-box RNA helicase that can bind and unwind G4-quadruplexes in DNA and RNA. To detect novel RNA targets of RHAU, we performed an RNA co-immunoprecipitation screen and identified the PITX1 messenger RNA (mRNA) as specifically and highly enriched. PITX1 is a homeobox transcription factor with roles in both development and cancer. Primary sequence analysis identified three probable quadruplexes within the 3′-untranslated region of the PITX1 mRNA. Each of these sequences, when isolated, forms stable quadruplex structures that interact with RHAU. We provide evidence that these quadruplexes exist in the endogenous mRNA; however, we discovered that RHAU is tethered to the mRNA via an alternative non–quadruplex-forming region. RHAU knockdown by small interfering RNA results in significant increases in PITX1 protein levels with only marginal changes in mRNA, suggesting a role for RHAU in translational regulation. Involvement of components of the microRNA machinery is supported by similar and non-additive increases in PITX1 protein expression on Dicer and combined RHAU/Dicer knockdown. We also demonstrate a requirement of argonaute-2, a key RNA-induced silencing complex component, to mediate RHAU-dependent changes in PITX1 protein levels. These results demonstrate a novel role for RHAU in microRNA-mediated translational regulation at a quadruplex-containing 3′-untranslated region.
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Affiliation(s)
- Evan P Booy
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada, University of Manitoba, Winnipeg, Manitoba, Canada, Department of Biochemistry and Molecular Biology, University of British Columbia, V6T 1Z4 Vancouver, British Columbia, Canada and Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2
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64
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Fujita H, Imaizumi Y, Kasahara Y, Kitadume S, Ozaki H, Kuwahara M, Sugimoto N. Structural and affinity analyses of g-quadruplex DNA aptamers for camptothecin derivatives. Pharmaceuticals (Basel) 2013; 6:1082-93. [PMID: 24276420 PMCID: PMC3818834 DOI: 10.3390/ph6091082] [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: 07/01/2013] [Revised: 08/11/2013] [Accepted: 08/26/2013] [Indexed: 01/13/2023] Open
Abstract
We recently selected DNA aptamers that bind to camptothecin (CPT) and CPT derivatives from a 70-mer oligodeoxyribonucleotide (ODN) library using the Systematic Evolution of Ligands by EXponential enrichment (SELEX) method. The target-binding activity of the obtained 70-mer CPT-binding DNA aptamer, termed CA-70, which contains a 16-mer guanine (G)-core motif (G3TG3TG3T2G3) that forms a three-tiered G-quadruplex, was determined using fluorescence titration. In this study, truncated fragments of CA-70 that all have the G-core motif, CA-40, -20, -19, -18A, -18B, -17, and -16, were carefully analyzed. We found that CA-40 retained the target-binding activity, whereas CA-20, -19, and -18B exhibited little or no binding activities. Further, not only CA-18A but also the shorter length fragments CA-17 and -16 clearly retained the binding activity, indicating that tail strands of the G-quadruplex structure can significantly affect the target binding of G-quadruplex DNA aptamers. Further analyses using circular dichroism (CD) spectroscopy and fluorescence polarization (FP) assay were conducted to investigate the structure and affinity of G-quadruplex DNA aptamers.
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Affiliation(s)
- Hiroto Fujita
- Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan.
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65
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Bharti SK, Sommers JA, George F, Kuper J, Hamon F, Shin-ya K, Teulade-Fichou MP, Kisker C, Brosh RM. Specialization among iron-sulfur cluster helicases to resolve G-quadruplex DNA structures that threaten genomic stability. J Biol Chem 2013; 288:28217-29. [PMID: 23935105 DOI: 10.1074/jbc.m113.496463] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G-quadruplex (G4) DNA, an alternate structure formed by Hoogsteen hydrogen bonds between guanines in G-rich sequences, threatens genomic stability by perturbing normal DNA transactions including replication, repair, and transcription. A variety of G4 topologies (intra- and intermolecular) can form in vitro, but the molecular architecture and cellular factors influencing G4 landscape in vivo are not clear. Helicases that unwind structured DNA molecules are emerging as an important class of G4-resolving enzymes. The BRCA1-associated FANCJ helicase is among those helicases able to unwind G4 DNA in vitro, and FANCJ mutations are associated with breast cancer and linked to Fanconi anemia. FANCJ belongs to a conserved iron-sulfur (Fe S) cluster family of helicases important for genomic stability including XPD (nucleotide excision repair), DDX11 (sister chromatid cohesion), and RTEL (telomere metabolism), genetically linked to xeroderma pigmentosum/Cockayne syndrome, Warsaw breakage syndrome, and dyskeratosis congenita, respectively. To elucidate the role of FANCJ in genomic stability, its molecular functions in G4 metabolism were examined. FANCJ efficiently unwound in a kinetic and ATPase-dependent manner entropically favored unimolecular G4 DNA, whereas other Fe-S helicases tested did not. The G4-specific ligands Phen-DC3 or Phen-DC6 inhibited FANCJ helicase on unimolecular G4 ∼1000-fold better than bi- or tetramolecular G4 DNA. The G4 ligand telomestatin induced DNA damage in human cells deficient in FANCJ but not DDX11 or XPD. These findings suggest FANCJ is a specialized Fe-S cluster helicase that preserves chromosomal stability by unwinding unimolecular G4 DNA likely to form in transiently unwound single-stranded genomic regions.
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Affiliation(s)
- Sanjay Kumar Bharti
- From the Laboratory of Molecular Gerontology, NIA, National Institutes of Health, National Institutes of Health Biomedical Research Center, Baltimore, Maryland 21224
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66
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Sengupta B, Pahari B, Blackmon L, Sengupta PK. Prospect of bioflavonoid fisetin as a quadruplex DNA ligand: a biophysical approach. PLoS One 2013; 8:e65383. [PMID: 23785423 PMCID: PMC3681855 DOI: 10.1371/journal.pone.0065383] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 04/24/2013] [Indexed: 01/30/2023] Open
Abstract
Quadruplex (G4) forming sequences in telomeric DNA and c-myc promoter regions of human DNA are associated with tumorogenesis. Ligands that can facilitate or stabilize the formation and increase the stabilization of G4 can prevent tumor cell proliferation and have been regarded as potential anti-cancer drugs. In the present study, steady state and time-resolved fluorescence measurements provide important structural and dynamical insights into the free and bound states of the therapeutically potent plant flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) in a G4 DNA matrix. The excited state intra-molecular proton transfer (ESPT) of fisetin plays an important role in observing and understanding the binding of fisetin with the G4 DNA. Differential absorption spectra, thermal melting, and circular dichroism spectroscopic studies provide evidences for the formation of G4 DNA and size exclusion chromatography (SEC) proves the binding and 1∶1 stoichiometry of fisetin in the DNA matrix. Comparative analysis of binding in the presence of EtBr proves that fisetin favors binding at the face of the G-quartet, mostly along the diagonal loop. Time resolved fluorescence anisotropy decay analysis indicates the increase in the restrictions in motion from the free to bound fisetin. We have also investigated the fingerprints of the binding of fisetin in the antiparallel quadruplex using Raman spectroscopy. Preliminary results indicate fisetin to be a prospective candidate as a G4 ligand.
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Affiliation(s)
- Bidisha Sengupta
- Department of Chemistry, Tougaloo College, Tougaloo, Mississippi, United States of America
| | - Biswapathik Pahari
- Biophysics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, West Bengal, India
| | - Laura Blackmon
- Department of Chemistry, Tougaloo College, Tougaloo, Mississippi, United States of America
| | - Pradeep K. Sengupta
- Biophysics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, West Bengal, India
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67
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Vummidi BR, Alzeer J, Luedtke NW. Fluorescent Probes for G-Quadruplex Structures. Chembiochem 2013; 14:540-58. [DOI: 10.1002/cbic.201200612] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Indexed: 12/19/2022]
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68
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Cavaliere P, Pagano B, Granata V, Prigent S, Rezaei H, Giancola C, Zagari A. Cross-talk between prion protein and quadruplex-forming nucleic acids: a dynamic complex formation. Nucleic Acids Res 2012; 41:327-39. [PMID: 23104426 PMCID: PMC3592392 DOI: 10.1093/nar/gks970] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Prion protein (PrP) is involved in lethal neurodegenerative diseases, and many issues remain unclear about its physio-pathological role. Quadruplex-forming nucleic acids (NAs) have been found to specifically bind to both PrP cellular and pathological isoforms. To clarify the relevance of these interactions, thermodynamic, kinetic and structural studies have been performed, using isothermal titration calorimetry, surface plasmon resonance and circular dichroism methodologies. Three quadruplex-forming sequences, d(TGGGGT), r(GGAGGAGGAGGA), d(GGAGGAGGAGGA), and various forms of PrP were selected for this study. Our results showed that these quadruplexes exhibit a high affinity and specificity toward PrP, with KD values within the range 62÷630 nM, and a weaker affinity toward a PrP-β oligomer, which mimics the pathological isoform. We demonstrated that the NA quadruplex architecture is the structural determinant for the recognition by both PrP isoforms. Furthermore, we spotted both PrP N-terminal and C-terminal domains as the binding regions involved in the interaction with DNA/RNAs, using several PrP truncated forms. Interestingly, a reciprocally induced structure loss was observed upon PrP–NA interaction. Our results allowed to surmise a quadruplex unwinding-activity of PrP, that may have a feedback in vivo.
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Affiliation(s)
- Paola Cavaliere
- Dipartimento delle Scienze Biologiche, Università degli Studi di Napoli Federico II, Naples 80134, Italy
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69
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Abstract
The DEAH helicase RHAU (alias DHX36, G4R1) is the only helicase shown to have G-quadruplex (G4)-RNA resolvase activity and the major source of G4-DNA resolvase activity. Previous report showed RHAU mRNA expression to be elevated in human lymphoid and CD34(+) BM cells, suggesting a potential role in hematopoiesis. Here, we generated a conditional knockout of the RHAU gene in mice. Germ line deletion of RHAU led to embryonic lethality. We then targeted the RHAU gene specifically in the hematopoiesis system, using a Cre-inducible system in which an optimized variant of Cre recombinase was expressed under the control of the Vav1 promoter. RHAU deletion in hematopoietic system caused hemolytic anemia and differentiation defect at the proerythroblast stage. The partial differentiation block of proerythroblasts was because of a proliferation defect. Transcriptome analysis of RHAU knockout proerythroblasts showed that a statistically significant portion of the deregulated genes contain G4 motifs in their promoters. This suggests that RHAU may play a role in the regulation of gene expression that relies on its G4 resolvase activity.
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70
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Booy EP, Meier M, Okun N, Novakowski SK, Xiong S, Stetefeld J, McKenna SA. The RNA helicase RHAU (DHX36) unwinds a G4-quadruplex in human telomerase RNA and promotes the formation of the P1 helix template boundary. Nucleic Acids Res 2012; 40:4110-24. [PMID: 22238380 PMCID: PMC3351167 DOI: 10.1093/nar/gkr1306] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Human telomerase RNA (hTR) contains several guanine tracts at its 5′-end that can form a G4-quadruplex structure. Previous evidence suggests that a G4-quadruplex within this region disrupts the formation of an important structure within hTR known as the P1 helix, a critical element in defining the template boundary for reverse transcription. RNA associated with AU-rich element (RHAU) is an RNA helicase that has specificity for DNA and RNA G4-quadruplexes. Two recent studies identify a specific interaction between hTR and RHAU. Herein, we confirm this interaction and identify the minimally interacting RNA fragments. We demonstrate the existence of multiple quadruplex structures within the 5′ region of hTR and find that these regions parallel the minimal sequences capable of RHAU interaction. We confirm the importance of the RHAU-specific motif in the interaction with hTR and demonstrate that the helicase activity of RHAU is sufficient to unwind the quadruplex and promote an interaction with 25 internal nucleotides to form a stable P1 helix. Furthermore, we have found that a 5′-terminal quadruplex persists following P1 helix formation that retains affinity for RHAU. Finally, we have investigated the functional implications of this interaction and demonstrated a reduction in average telomere length following RHAU knockdown by small interfering RNA (siRNA).
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Affiliation(s)
- E P Booy
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada
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71
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Huang W, Smaldino PJ, Zhang Q, Miller LD, Cao P, Stadelman K, Wan M, Giri B, Lei M, Nagamine Y, Vaughn JP, Akman SA, Sui G. Yin Yang 1 contains G-quadruplex structures in its promoter and 5'-UTR and its expression is modulated by G4 resolvase 1. Nucleic Acids Res 2011; 40:1033-49. [PMID: 21993297 PMCID: PMC3273823 DOI: 10.1093/nar/gkr849] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Yin Yang 1 (YY1) is a multifunctional protein with regulatory potential in tumorigenesis. Ample studies demonstrated the activities of YY1 in regulating gene expression and mediating differential protein modifications. However, the mechanisms underlying YY1 gene expression are relatively understudied. G-quadruplexes (G4s) are four-stranded structures or motifs formed by guanine-rich DNA or RNA domains. The presence of G4 structures in a gene promoter or the 5′-UTR of its mRNA can markedly affect its expression. In this report, we provide strong evidence showing the presence of G4 structures in the promoter and the 5′-UTR of YY1. In reporter assays, mutations in these G4 structure forming sequences increased the expression of Gaussia luciferase (Gluc) downstream of either YY1 promoter or 5′-UTR. We also discovered that G4 Resolvase 1 (G4R1) enhanced the Gluc expression mediated by the YY1 promoter, but not the YY1 5′-UTR. Consistently, G4R1 binds the G4 motif of the YY1 promoter in vitro and ectopically expressed G4R1 increased endogenous YY1 levels. In addition, the analysis of a gene array data consisting of the breast cancer samples of 258 patients also indicates a significant, positive correlation between G4R1 and YY1 expression.
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Affiliation(s)
- Weiwei Huang
- Department of Cancer Biology and Comprehensive Cancer Center, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Lattmann S, Stadler MB, Vaughn JP, Akman SA, Nagamine Y. The DEAH-box RNA helicase RHAU binds an intramolecular RNA G-quadruplex in TERC and associates with telomerase holoenzyme. Nucleic Acids Res 2011; 39:9390-404. [PMID: 21846770 PMCID: PMC3241650 DOI: 10.1093/nar/gkr630] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Guanine-quadruplexes (G4) consist of non-canonical four-stranded helical arrangements of guanine-rich nucleic acid sequences. The bulky and thermodynamically stable features of G4 structures have been shown in many respects to affect normal nucleic acid metabolism. In vivo conversion of G4 structures to single-stranded nucleic acid requires specialized proteins with G4 destabilizing/unwinding activity. RHAU is a human DEAH-box RNA helicase that exhibits G4-RNA binding and resolving activity. In this study, we employed RIP-chip analysis to identify en masse RNAs associated with RHAU in vivo. Approximately 100 RNAs were found to be associated with RHAU and bioinformatics analysis revealed that the majority contained potential G4-forming sequences. Among the most abundant RNAs selectively enriched with RHAU, we identified the human telomerase RNA template TERC as a true target of RHAU. Remarkably, binding of RHAU to TERC depended on the presence of a stable G4 structure in the 5′-region of TERC, both in vivo and in vitro. RHAU was further found to associate with the telomerase holoenzyme via the 5′-region of TERC. Collectively, these results provide the first evidence that intramolecular G4-RNAs serve as physiologically relevant targets for RHAU. Furthermore, our results suggest the existence of alternatively folded forms of TERC in the fully assembled telomerase holoenyzme.
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Affiliation(s)
- Simon Lattmann
- Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Maulbeerstrasse 66, 4058 Basel, Switzerland.
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