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Duan M, Li Y, Zhang F, Huang Q. Assessing B-Z DNA Transitions in Solutions via Infrared Spectroscopy. Biomolecules 2023; 13:964. [PMID: 37371544 DOI: 10.3390/biom13060964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 05/25/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
Z-DNA refers to the left-handed double-helix DNA that has attracted much attention because of its association with some specific biological functions. However, because of its low content and unstable conformation, Z-DNA is normally difficult to observe or identify. Up to now, there has been a lack of unified or standard analytical methods among diverse techniques for probing Z-DNA and its transformation conveniently. In this work, NaCl, MgCl2, and ethanol were utilized to induce d(GC)8 from B-DNA to Z-DNA in vitro, and Fourier transform infrared (FTIR) spectroscopy was employed to monitor the transformation of Z-DNA under different induction conditions. The structural changes during the transformation process were carefully examined, and the DNA chirality alterations were validated by the circular dichroism (CD) measurements. The Z-DNA characteristic signals in the 1450 cm-1-900 cm-1 region of the d(GC)8 infrared (IR) spectrum were observed, which include the peaks at 1320 cm-1, 1125 cm-1 and 925 cm-1, respectively. The intensity ratios of A1320/A970, A1125/A970, and A925/A970 increased with Z-DNA content in the transition process. Furthermore, compared with the CD spectra, the IR spectra showed higher sensitivity to Z-DNA, providing more information about the molecular structure change of DNA. Therefore, this study has established a more reliable FTIR analytical approach to assess BZ DNA conformational changes in solutions, which may help the understanding of the Z-DNA transition mechanism and promote the study of Z-DNA functions in biological systems.
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Affiliation(s)
- Mengmeng Duan
- Henan Key Laboratory of Ion-Beam Bioengineering, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China
| | - Yalin Li
- School of Food and Biological Engineering, Henan University of Animal Husbandry and Economy, Zhengzhou 450047, China
| | - Fengqiu Zhang
- Henan Key Laboratory of Ion-Beam Bioengineering, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China
| | - Qing Huang
- CAS Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Institute of Intelligent Machines, Hefei Institutes of Physical Sciences, Chinese Academy of Sciences, Hefei 230031, China
- Science Island Branch of Graduate School, University of Science and Technology, Hefei 230026, China
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2
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Wang G, Vasquez KM. Dynamic alternative DNA structures in biology and disease. Nat Rev Genet 2023; 24:211-234. [PMID: 36316397 DOI: 10.1038/s41576-022-00539-9] [Citation(s) in RCA: 55] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2022] [Indexed: 11/06/2022]
Abstract
Repetitive elements in the human genome, once considered 'junk DNA', are now known to adopt more than a dozen alternative (that is, non-B) DNA structures, such as self-annealed hairpins, left-handed Z-DNA, three-stranded triplexes (H-DNA) or four-stranded guanine quadruplex structures (G4 DNA). These dynamic conformations can act as functional genomic elements involved in DNA replication and transcription, chromatin organization and genome stability. In addition, recent studies have revealed a role for these alternative structures in triggering error-generating DNA repair processes, thereby actively enabling genome plasticity. As a driving force for genetic variation, non-B DNA structures thus contribute to both disease aetiology and evolution.
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Affiliation(s)
- Guliang Wang
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Paediatric Research Institute, Austin, TX, USA
| | - Karen M Vasquez
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Paediatric Research Institute, Austin, TX, USA.
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3
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High-throughput techniques enable advances in the roles of DNA and RNA secondary structures in transcriptional and post-transcriptional gene regulation. Genome Biol 2022; 23:159. [PMID: 35851062 PMCID: PMC9290270 DOI: 10.1186/s13059-022-02727-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 07/07/2022] [Indexed: 12/27/2022] Open
Abstract
The most stable structure of DNA is the canonical right-handed double helix termed B DNA. However, certain environments and sequence motifs favor alternative conformations, termed non-canonical secondary structures. The roles of DNA and RNA secondary structures in transcriptional regulation remain incompletely understood. However, advances in high-throughput assays have enabled genome wide characterization of some secondary structures. Here, we describe their regulatory functions in promoters and 3’UTRs, providing insights into key mechanisms through which they regulate gene expression. We discuss their implication in human disease, and how advances in molecular technologies and emerging high-throughput experimental methods could provide additional insights.
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4
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Georgakopoulos-Soares I, Victorino J, Parada GE, Agarwal V, Zhao J, Wong HY, Umar MI, Elor O, Muhwezi A, An JY, Sanders SJ, Kwok CK, Inoue F, Hemberg M, Ahituv N. High-throughput characterization of the role of non-B DNA motifs on promoter function. CELL GENOMICS 2022; 2:100111. [PMID: 35573091 PMCID: PMC9105345 DOI: 10.1016/j.xgen.2022.100111] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 10/21/2021] [Accepted: 02/18/2022] [Indexed: 12/24/2022]
Abstract
lternative DNA conformations, termed non-B DNA structures, can affect transcription, but the underlying mechanisms and their functional impact have not been systematically characterized. Here, we used computational genomic analyses coupled with massively parallel reporter assays (MPRAs) to show that certain non-B DNA structures have a substantial effect on gene expression. Genomic analyses found that non-B DNA structures at promoters harbor an excess of germline variants. Analysis of multiple MPRAs, including a promoter library specifically designed to perturb non-B DNA structures, functionally validated that Z-DNA can significantly affect promoter activity. We also observed that biophysical properties of non-B DNA motifs, such as the length of Z-DNA motifs and the orientation of G-quadruplex structures relative to transcriptional direction, have a significant effect on promoter activity. Combined, their higher mutation rate and functional effect on transcription implicate a subset of non-B DNA motifs as major drivers of human gene-expression-associated phenotypes.
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Affiliation(s)
- Ilias Georgakopoulos-Soares
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
| | - Jesus Victorino
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
- Departamento de Bioquímica, Facultad de Medicina, Universidad Autónoma de Madrid (UAM), 28029 Madrid, Spain
| | - Guillermo E. Parada
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton CB10 1SA, UK
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | | | - Jingjing Zhao
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
| | - Hei Yuen Wong
- Department of Chemistry and State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon Tong, Hong Kong SAR, China
| | - Mubarak Ishaq Umar
- Department of Chemistry and State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon Tong, Hong Kong SAR, China
| | - Orry Elor
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
| | - Allan Muhwezi
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton CB10 1SA, UK
| | - Joon-Yong An
- Department of Psychiatry, UCSF Weill Institute for Neurosciences, University of California San Francisco, San Francisco, CA, USA
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, Republic of Korea
| | - Stephan J. Sanders
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
- Department of Psychiatry, UCSF Weill Institute for Neurosciences, University of California San Francisco, San Francisco, CA, USA
| | - Chun Kit Kwok
- Department of Chemistry and State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon Tong, Hong Kong SAR, China
- Shenzhen Research Institute of City University of Hong Kong, Shenzhen, China
| | - Fumitaka Inoue
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
| | - Martin Hemberg
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton CB10 1SA, UK
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Nadav Ahituv
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
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5
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Liu M, Cui Y, Zhang Y, An R, Li L, Park S, Sugiyama H, Liang X. Single base-modification reports and locates Z-DNA conformation on a Z-B-chimera formed by topological constraint. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2022. [DOI: 10.1246/bcsj.20210400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Mengqin Liu
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Yixiao Cui
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Yaping Zhang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Ran An
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
- Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, P. R. China
| | - Lin Li
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Soyoung Park
- Immunology Frontier Research Center, Osaka University, 3-1, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Xingguo Liang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
- Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, P. R. China
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6
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Li L, Zhang Y, Ma W, Chen H, Liu M, An R, Cheng B, Liang X. Nonalternating purine pyrimidine sequences can form stable left-handed DNA duplex by strong topological constraint. Nucleic Acids Res 2021; 50:684-696. [PMID: 34967416 PMCID: PMC8789069 DOI: 10.1093/nar/gkab1283] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 12/01/2021] [Accepted: 12/16/2021] [Indexed: 11/14/2022] Open
Abstract
In vivo, left-handed DNA duplex (usually refers to Z-DNA) is mainly formed in the region of DNA with alternating purine pyrimidine (APP) sequence and plays significant biological roles. It is well known that d(CG)n sequence can form Z-DNA most easily under negative supercoil conditions, but its essence has not been well clarified. The study on sequence dependence of Z-DNA stability is very difficult without modification or inducers. Here, by the strong topological constraint caused by hybridization of two complementary short circular ssDNAs, left-handed duplex part was generated for various sequences, and their characteristics were investigated by using gel-shift after binding to specific proteins, CD and Tm analysis, and restriction enzyme cleavage. Under the strong topological constraint, non-APP sequences can also form left-handed DNA duplex as stable as that of APP sequences. As compared with non-APP sequences, the thermal stability difference for APP sequences between Z-form and B-form is smaller, which may be the reason that Z-DNA forms preferentially for APP ones. This result can help us to understand why nature selected APP sequences to regulate gene expression by transient Z-DNA formation, as well as why polymer with chirality can usually form both duplexes with left- or right-handed helix.
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Affiliation(s)
- Lin Li
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Yaping Zhang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Wanzhi Ma
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Hui Chen
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Mengqin Liu
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Ran An
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, China
| | - Bingxiao Cheng
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Xingguo Liang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, China
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7
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Kim SH, Jung HJ, Lee IB, Lee NK, Hong SC. Sequence-dependent cost for Z-form shapes the torsion-driven B-Z transition via close interplay of Z-DNA and DNA bubble. Nucleic Acids Res 2021; 49:3651-3660. [PMID: 33744929 PMCID: PMC8053131 DOI: 10.1093/nar/gkab153] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 02/19/2021] [Accepted: 02/27/2021] [Indexed: 02/06/2023] Open
Abstract
Despite recent genome-wide investigations of functional DNA elements, the mechanistic details about their actions remain elusive. One intriguing possibility is that DNA sequences with special patterns play biological roles, adopting non-B-DNA conformations. Here we investigated dynamics of thymine-guanine (TG) repeats, microsatellite sequences and recurrently found in promoters, as well as cytosine–guanine (CG) repeats, best-known Z-DNA forming sequence, in the aspect of Z-DNA formation. We measured the energy barriers of the B–Z transition with those repeats and discovered the sequence-dependent penalty for Z-DNA generates distinctive thermodynamic and kinetic features in the torque-induced transition. Due to the higher torsional stress required for Z-form in TG repeats, a bubble could be induced more easily, suppressing Z-DNA induction, but facilitate the B–Z interconversion kinetically at the transition midpoint. Thus, the Z-form by TG repeats has advantages as a torsion buffer and bubble selector while the Z-form by CG repeats likely behaves as torsion absorber. Our statistical physics model supports quantitatively the populations of Z-DNA and reveals the pivotal roles of bubbles in state dynamics. All taken together, a quantitative picture for the transition was deduced within the close interplay among bubbles, plectonemes and Z-DNA.
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Affiliation(s)
- Sook Ho Kim
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841 Korea.,Department of Physics, Korea University, Seoul, 02841 Korea.,GRI-TPC International Research Center, Sejong University, Seoul, 05006 Korea
| | - Hae Jun Jung
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841 Korea.,Department of Physics, Korea University, Seoul, 02841 Korea
| | - Il-Buem Lee
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841 Korea.,Department of Physics, Korea University, Seoul, 02841 Korea
| | - Nam-Kyung Lee
- Department of Physics and Astronomy, Sejong University, Seoul, 05006 Korea
| | - Seok-Cheol Hong
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841 Korea.,Department of Physics, Korea University, Seoul, 02841 Korea
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8
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Matsumoto S, Sugimoto N. New Insights into the Functions of Nucleic Acids Controlled by Cellular Microenvironments. Top Curr Chem (Cham) 2021; 379:17. [PMID: 33782792 DOI: 10.1007/s41061-021-00329-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 03/11/2021] [Indexed: 12/11/2022]
Abstract
The right-handed double-helical B-form structure (B-form duplex) has been widely recognized as the canonical structure of nucleic acids since it was first proposed by James Watson and Francis Crick in 1953. This B-form duplex model has a monochronic and static structure and codes genetic information within a sequence. Interestingly, DNA and RNA can form various non-canonical structures, such as hairpin loops, left-handed helices, triplexes, tetraplexes of G-quadruplex and i-motif, and branched junctions, in addition to the canonical structure. The formation of non-canonical structures depends not only on sequence but also on the surrounding environment. Importantly, these non-canonical structures may exhibit a wide variety of biological roles by changing their structures and stabilities in response to the surrounding environments, which undergo vast changes at specific locations and at specific times in cells. Here, we review recent progress regarding the interesting behaviors and functions of nucleic acids controlled by molecularly crowded cellular conditions. New insights gained from recent studies suggest that nucleic acids not only code genetic information in sequences but also have unknown functions regarding their structures and stabilities through drastic structural changes in cellular environments.
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Affiliation(s)
- Saki Matsumoto
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 7-1-20 Minatojima-Minamimachi, Kobe, 650-0047, Japan
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 7-1-20 Minatojima-Minamimachi, Kobe, 650-0047, Japan. .,Graduate School of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, 7-1-20 Minatojima-Minamimachi, Kobe, 650-0047, Japan.
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9
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Herbert A. ALU non-B-DNA conformations, flipons, binary codes and evolution. ROYAL SOCIETY OPEN SCIENCE 2020; 7:200222. [PMID: 32742689 PMCID: PMC7353975 DOI: 10.1098/rsos.200222] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 05/18/2020] [Indexed: 05/08/2023]
Abstract
ALUs contribute to genetic diversity by altering DNA's linear sequence through retrotransposition, recombination and repair. ALUs also have the potential to form alternative non-B-DNA conformations such as Z-DNA, triplexes and quadruplexes that alter the read-out of information from the genome. I suggest here these structures enable the rapid reprogramming of cellular pathways to offset DNA damage and regulate inflammation. The experimental data supporting this form of genetic encoding is presented. ALU sequence motifs that form non-B-DNA conformations under physiological conditions are called flipons. Flipons are binary switches. They are dissipative structures that trade energy for information. By efficiently targeting cellular machines to active genes, flipons expand the repertoire of RNAs compiled from a gene. Their action greatly increases the informational capacity of linearly encoded genomes. Flipons are programmable by epigenetic modification, synchronizing cellular events by altering both chromatin state and nucleosome phasing. Different classes of flipon exist. Z-flipons are based on Z-DNA and modify the transcripts compiled from a gene. T-flipons are based on triplexes and localize non-coding RNAs that direct the assembly of cellular machines. G-flipons are based on G-quadruplexes and sense DNA damage, then trigger the appropriate protective responses. Flipon conformation is dynamic, changing with context. When frozen in one state, flipons often cause disease. The propagation of flipons throughout the genome by ALU elements represents a novel evolutionary innovation that allows for rapid change. Each ALU insertion creates variability by extracting a different set of information from the neighbourhood in which it lands. By elaborating on already successful adaptations, the newly compiled transcripts work with the old to enhance survival. Systems that optimize flipon settings through learning can adapt faster than with other forms of evolution. They avoid the risk of relying on random and irreversible codon rewrites.
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10
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Dynamic regulation of Z-DNA in the mouse prefrontal cortex by the RNA-editing enzyme Adar1 is required for fear extinction. Nat Neurosci 2020; 23:718-729. [PMID: 32367065 PMCID: PMC7269834 DOI: 10.1038/s41593-020-0627-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 03/19/2020] [Indexed: 01/06/2023]
Abstract
DNA forms conformational states beyond the right-handed double-helix; however, the functional relevance of these non-canonical structures in the brain remains unknown. We show that, in the prefrontal cortex of mice, the formation of one such structure, Z-DNA, is involved in the regulation of extinction memory. Z-DNA is formed during fear learning, and reduced during extinction learning, which is mediated, in part, by a direct interaction between Z-DNA and the RNA editing enzyme Adar1. Adar1 binds to Z-DNA during fear extinction learning which leads to a reduction in Z-DNA at sites where Adar1 is recruited. Knockdown of Adar1 leads to an inability to modify a previously acquired fear memory and blocks activity-dependent changes in DNA structure and RNA state; effects that are fully rescued by the introduction of full-length Adar1. These findings suggest a novel mechanism of learning-induced gene regulation dependent on both proteins which recognize DNA structure, and the state.
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11
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Hanawalt P. Repairing DNA for 80 years: The timeline of my life. DNA Repair (Amst) 2020. [DOI: 10.1016/j.dnarep.2019.102783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Distinct DNA repair pathways cause genomic instability at alternative DNA structures. Nat Commun 2020; 11:236. [PMID: 31932649 PMCID: PMC6957503 DOI: 10.1038/s41467-019-13878-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 11/05/2019] [Indexed: 01/01/2023] Open
Abstract
Alternative DNA structure-forming sequences can stimulate mutagenesis and are enriched at mutation hotspots in human cancer genomes, implicating them in disease etiology. However, the mechanisms involved are not well characterized. Here, we discover that Z-DNA is mutagenic in yeast as well as human cells, and that the nucleotide excision repair complex, Rad10-Rad1(ERCC1-XPF), and the mismatch repair complex, Msh2-Msh3, are required for Z-DNA-induced genetic instability in yeast and human cells. Both ERCC1-XPF and MSH2-MSH3 bind to Z-DNA-forming sequences, though ERCC1-XPF recruitment to Z-DNA is dependent on MSH2-MSH3. Moreover, ERCC1-XPF-dependent DNA strand-breaks occur near the Z-DNA-forming region in human cell extracts, and we model these interactions at the sub-molecular level. We propose a relationship in which these complexes recognize and process Z-DNA in eukaryotes, representing a mechanism of Z-DNA-induced genomic instability.
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13
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Abstract
Left-handed Z-DNA/Z-RNA is bound with high affinity by the Zα domain protein family that includes ADAR (a double-stranded RNA editing enzyme), ZBP1 and viral orthologs regulating innate immunity. Loss-of-function mutations in ADAR p150 allow persistent activation of the interferon system by Alu dsRNAs and are causal for Aicardi-Goutières Syndrome. Heterodimers of ADAR and DICER1 regulate the switch from RNA- to protein-centric immunity. Loss of DICER1 function produces age-related macular degeneration, a different type of Alu-mediated disease. The overlap of Z-forming sites with those for the signal recognition particle likely limits invasion of primate genomes by Alu retrotransposons.
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Affiliation(s)
- Alan Herbert
- Discovery, InsideOutBio, 42, 8th Street, Unit 3412, Charlestown, MA 02129 USA
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14
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Huang S, Fu Q, Cheng F, Wan Y, Quan W, Hu C, Li D. d(GC)10 sequence within promoter region enhances the promoter activity in Saccharomyces cerevisiae. Acta Biochim Biophys Sin (Shanghai) 2018; 50:1288-1290. [PMID: 30364938 DOI: 10.1093/abbs/gmy134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- Shenghe Huang
- Department of Basic Medicine, JiangXi College of Traditional Chinese Medicine, Fuzhou, China
| | - Qiang Fu
- Department of Basic Medicine, JiangXi College of Traditional Chinese Medicine, Fuzhou, China
| | - Feng Cheng
- Department of Basic Medicine, Fuzhou Medical College, Nanchang University, Fuzhou, China
| | - Yizhou Wan
- Department of Basic Medicine, Fuzhou Medical College, Nanchang University, Fuzhou, China
| | - Wenjun Quan
- Department of Basic Medicine, Fuzhou Medical College, Nanchang University, Fuzhou, China
| | - Chengyu Hu
- Department of Bioscience, College of Life Science, Nanchang University, Nanchang, China
| | - Dongming Li
- Department of Basic Medicine, Fuzhou Medical College, Nanchang University, Fuzhou, China
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15
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Gurbanov R, S Ozek N, Tunçer S, Severcan F, Gozen AG. Aspects of silver tolerance in bacteria: infrared spectral changes and epigenetic clues. JOURNAL OF BIOPHOTONICS 2018; 11:e201700252. [PMID: 29243883 DOI: 10.1002/jbio.201700252] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 12/13/2017] [Indexed: 06/07/2023]
Abstract
In this study, the molecular profile changes leading to the adaptation of bacteria to survive and grow at inhibitory silver concentration were explored. The profile obtained through infrared (IR)-based measurements indicated extensive changes in all biomolecular components, which were supported by chemometric techniques. The changes in biomolecular profile were prominent, including nucleic acids. The changes in nucleic acid region (1350-950 cm-1 ) were encountered as a clue for conformational change in DNA. Further analysis of DNA by IR spectroscopy revealed changes in the backbone and sugar conformations. Moreover, Enzyme-Linked Immunosorbent Assay-based measurements of DNA methylation levels were performed to see if epigenetic mechanisms are in operation during bacterial adaptation to this environmental challenge. The results indicated a notable demethylation in Escherichia coli and methylation in Staphylococcus aureus likely to be associated with their elaborate adaptation process to sustain survival and growth.
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Affiliation(s)
- Rafig Gurbanov
- Department of Molecular Biology and Genetics, Bilecik Şeyh Edebali University, Bilecik, Turkey
- Department of Biological Sciences, Middle East Technical University, Ankara, Turkey
| | - Nihal S Ozek
- Department of Biology, Ataturk University, Erzurum, Turkey
| | - Sinem Tunçer
- Department of Biological Sciences, Middle East Technical University, Ankara, Turkey
| | - Feride Severcan
- Department of Biological Sciences, Middle East Technical University, Ankara, Turkey
- Department of Biophysics, Faculty of Medicine, Altinbas University, Istanbul, Turkey
| | - Ayse G Gozen
- Department of Biological Sciences, Middle East Technical University, Ankara, Turkey
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16
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Tateishi-Karimata H, Kawauchi K, Sugimoto N. Destabilization of DNA G-Quadruplexes by Chemical Environment Changes during Tumor Progression Facilitates Transcription. J Am Chem Soc 2017; 140:642-651. [DOI: 10.1021/jacs.7b09449] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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17
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Bagshaw AT. Functional Mechanisms of Microsatellite DNA in Eukaryotic Genomes. Genome Biol Evol 2017; 9:2428-2443. [PMID: 28957459 PMCID: PMC5622345 DOI: 10.1093/gbe/evx164] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2017] [Indexed: 02/06/2023] Open
Abstract
Microsatellite repeat DNA is best known for its length mutability, which is implicated in several neurological diseases and cancers, and often exploited as a genetic marker. Less well-known is the body of work exploring the widespread and surprisingly diverse functional roles of microsatellites. Recently, emerging evidence includes the finding that normal microsatellite polymorphism contributes substantially to the heritability of human gene expression on a genome-wide scale, calling attention to the task of elucidating the mechanisms involved. At present, these are underexplored, but several themes have emerged. I review evidence demonstrating roles for microsatellites in modulation of transcription factor binding, spacing between promoter elements, enhancers, cytosine methylation, alternative splicing, mRNA stability, selection of transcription start and termination sites, unusual structural conformations, nucleosome positioning and modification, higher order chromatin structure, noncoding RNA, and meiotic recombination hot spots.
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18
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Effects of Replication and Transcription on DNA Structure-Related Genetic Instability. Genes (Basel) 2017; 8:genes8010017. [PMID: 28067787 PMCID: PMC5295012 DOI: 10.3390/genes8010017] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/21/2016] [Accepted: 12/26/2016] [Indexed: 12/20/2022] Open
Abstract
Many repetitive sequences in the human genome can adopt conformations that differ from the canonical B-DNA double helix (i.e., non-B DNA), and can impact important biological processes such as DNA replication, transcription, recombination, telomere maintenance, viral integration, transposome activation, DNA damage and repair. Thus, non-B DNA-forming sequences have been implicated in genetic instability and disease development. In this article, we discuss the interactions of non-B DNA with the replication and/or transcription machinery, particularly in disease states (e.g., tumors) that can lead to an abnormal cellular environment, and how such interactions may alter DNA replication and transcription, leading to potential conflicts at non-B DNA regions, and eventually result in genetic stability and human disease.
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19
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Charnavets T, Nunvar J, Nečasová I, Völker J, Breslauer KJ, Schneider B. Conformational diversity of single-stranded DNA from bacterial repetitive extragenic palindromes: Implications for the DNA recognition elements of transposases. Biopolymers 2016; 103:585-96. [PMID: 25951997 PMCID: PMC4690160 DOI: 10.1002/bip.22666] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 05/05/2015] [Indexed: 01/19/2023]
Abstract
Repetitive extragenic palindrome (REP)—associated tyrosine transposase enzymes (RAYTs) bind REP DNA domains and catalyze their cleavage. Genomic sequence analyses identify potential noncoding REP sequences associated with RAYT-encoding genes. To probe the conformational space of potential RAYT DNA binding domains, we report here spectroscopic and calorimetric measurements that detect and partially characterize the solution conformational heterogeneity of REP oligonucleotides from six bacterial species. Our data reveal most of these REP oligonucleotides adopt multiple conformations, suggesting that RAYTs confront a landscape of potential DNA substrates in dynamic equilibrium that could be selected, enriched, and/or induced via differential binding. Thus, the transposase-bound DNA motif may not be the predominant conformation of the isolated REP domain. Intriguingly, for several REPs, the circular dichroism spectra suggest guanine tetraplexes as potential alternative or additional RAYT recognition elements, an observation consistent with these REP domains being highly nonrandom, with tetraplex-favoring 5′-G and 3′-C-rich segments. In fact, the conformational heterogeneity of REP domains detected and reported here, including the formation of noncanonical DNA secondary structures, may reflect a general feature required for recognition by RAYT transposases. Based on our biophysical data, we propose guanine tetraplexes as an additional DNA recognition element for binding by RAYT transposase enzymes. © 2015 Wiley Periodicals, Inc. Biopolymers 103: 585–596, 2015.
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Affiliation(s)
- Tatsiana Charnavets
- Institute of Biotechnology, Academy of Sciences of the Czech Republic, Videnska, 1083, 142 20 Prague, Czech Republic
| | - Jaroslav Nunvar
- Institute of Biotechnology, Academy of Sciences of the Czech Republic, Videnska, 1083, 142 20 Prague, Czech Republic
| | - Iva Nečasová
- Institute of Biotechnology, Academy of Sciences of the Czech Republic, Videnska, 1083, 142 20 Prague, Czech Republic
| | - Jens Völker
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Rd., Piscataway, NJ, 08854
| | - Kenneth J Breslauer
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Rd., Piscataway, NJ, 08854.,Cancer Institute of New Jersey, Rutgers University, New Brunswick, NJ, 08903
| | - Bohdan Schneider
- Institute of Biotechnology, Academy of Sciences of the Czech Republic, Videnska, 1083, 142 20 Prague, Czech Republic
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20
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Xu L, Wang W, Chong J, Shin JH, Xu J, Wang D. RNA polymerase II transcriptional fidelity control and its functional interplay with DNA modifications. Crit Rev Biochem Mol Biol 2015; 50:503-19. [PMID: 26392149 DOI: 10.3109/10409238.2015.1087960] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Accurate genetic information transfer is essential for life. As a key enzyme involved in the first step of gene expression, RNA polymerase II (Pol II) must maintain high transcriptional fidelity while it reads along DNA template and synthesizes RNA transcript in a stepwise manner during transcription elongation. DNA lesions or modifications may lead to significant changes in transcriptional fidelity or transcription elongation dynamics. In this review, we will summarize recent progress toward understanding the molecular basis of RNA Pol II transcriptional fidelity control and impacts of DNA lesions and modifications on Pol II transcription elongation.
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Affiliation(s)
- Liang Xu
- a Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California San Diego , La Jolla , CA , USA
| | - Wei Wang
- a Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California San Diego , La Jolla , CA , USA
| | - Jenny Chong
- a Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California San Diego , La Jolla , CA , USA
| | - Ji Hyun Shin
- a Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California San Diego , La Jolla , CA , USA
| | - Jun Xu
- a Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California San Diego , La Jolla , CA , USA
| | - Dong Wang
- a Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California San Diego , La Jolla , CA , USA
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21
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Abstract
Environmental agents are constantly challenging cells by damaging DNA, leading to the blockage of transcription elongation. How do cells deal with transcription-blockage and how is transcription restarted after the blocking lesions are removed? Here we review the processes responsible for the removal of transcription-blocking lesions, as well as mechanisms of transcription restart. We also discuss recent data suggesting that blocked RNA polymerases may not resume transcription from the site of the lesion following its removal but, rather, are forced to start over from the beginning of genes.
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22
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Huang S, Wu C, Li D, Wang H, Rao Z, Shen Q, Chen C, Liu Y, Xu X, Hu C. d(GC)n repeats form Z-DNA within promoter region and repress the promoter activity in Escherichia coli. Acta Biochim Biophys Sin (Shanghai) 2015; 47:567-9. [PMID: 26008205 DOI: 10.1093/abbs/gmv038] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Shenghe Huang
- Fuzhou Medical College, Nanchang University, Fuzhou 344000, China
| | - Chuxin Wu
- Nanchang Teachers College, Nanchang 330103, China
| | - Dongming Li
- Fuzhou Medical College, Nanchang University, Fuzhou 344000, China
| | - Haizhou Wang
- Department of Bioscience, College of Life Science, Nanchang University, Nanchang 330031, China
| | - Zechang Rao
- Fuzhou Medical College, Nanchang University, Fuzhou 344000, China
| | - Qiling Shen
- Fuzhou Medical College, Nanchang University, Fuzhou 344000, China
| | - Chunxiang Chen
- Fuzhou Medical College, Nanchang University, Fuzhou 344000, China
| | - Yong Liu
- Department of Bioscience, College of Life Science, Nanchang University, Nanchang 330031, China
| | - Xun Xu
- Fuzhou Medical College, Nanchang University, Fuzhou 344000, China
| | - Chengyu Hu
- Department of Bioscience, College of Life Science, Nanchang University, Nanchang 330031, China
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23
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Santillan BA, Moye C, Mittelman D, Wilson JH. GFP-based fluorescence assay for CAG repeat instability in cultured human cells. PLoS One 2014; 9:e113952. [PMID: 25423602 PMCID: PMC4244167 DOI: 10.1371/journal.pone.0113952] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 11/03/2014] [Indexed: 12/13/2022] Open
Abstract
Trinucleotide repeats can be highly unstable, mutating far more frequently than point mutations. Repeats typically mutate by addition or loss of units of the repeat. CAG repeat expansions in humans trigger neurological diseases that include myotonic dystrophy, Huntington disease, and several spinocerebellar ataxias. In human cells, diverse mechanisms promote CAG repeat instability, and in mice, the mechanisms of instability are varied and tissue-dependent. Dissection of mechanistic complexity and discovery of potential therapeutics necessitates quantitative and scalable screens for repeat mutation. We describe a GFP-based assay for screening modifiers of CAG repeat instability in human cells. The assay exploits an engineered intronic CAG repeat tract that interferes with expression of an inducible GFP minigene. Like the phenotypes of many trinucleotide repeat disorders, we find that GFP function is impaired by repeat expansion, in a length-dependent manner. The intensity of fluorescence varies inversely with repeat length, allowing estimates of repeat tract changes in live cells. We validate the assay using transcription through the repeat and engineered CAG-specific nucleases, which have previously been reported to induce CAG repeat instability. The assay is relatively fast and should be adaptable to large-scale screens of chemical and shRNA libraries.
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Affiliation(s)
- Beatriz A. Santillan
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Christopher Moye
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - David Mittelman
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia, United States of America
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - John H. Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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24
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Abstract
Understanding how DNA molecules interact with other biomolecules is related to how they utilize their functions and is therefore critical for understanding their structure-function relationships. For a long time, the existence of Z-form DNA (a left-handed double helical version of DNA, instead of the common right-handed B-form) has puzzled the scientists, and the definitive biological significance of Z-DNA has not yet been clarified. In this study, the effects of DNA conformation in DNA-DNA interactions are explored by molecular dynamics simulations. Using umbrella sampling, we find that for both B- and Z-form DNA, surrounding Mg(2+) ions always exert themselves to screen the Coulomb repulsion between DNA phosphates, resulting in very weak attractive force. On the contrary, a tight and stable bound state is discovered for Z-DNA in the presence of Mg(2+) or Na(+), benefiting from their hydrophobic nature. Based on the contact surface and a dewetting process analysis, a two-stage binding process of Z-DNA is outlined: two Z-DNA first attract each other through charge screening and Mg(2+) bridges to phosphate groups in the same way as that of B-DNA, after which hydrophobic contacts of the deoxyribose groups are formed via a dewetting effect, resulting in stable attraction between two Z-DNA molecules. The highlighted hydrophobic nature of Z-DNA interaction from the current study may help to understand the biological functions of Z-DNA in gene transcription.
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Affiliation(s)
- Weifeng Li
- Institute of Quantitative Biology and Medicine, School for Radiological & Interdisciplinary Sciences (RAD-X), Soochow University, Suzhou, China 215123
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25
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Iyer S, Doktycz MJ. Thrombin-mediated transcriptional regulation using DNA aptamers in DNA-based cell-free protein synthesis. ACS Synth Biol 2014; 3:340-6. [PMID: 24059754 DOI: 10.1021/sb4000756] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Realizing the potential of cell-free systems will require development of ligand-sensitive gene promoters that control gene expression in response to a ligand of interest. Here, we describe an approach to designing ligand-sensitive transcriptional control in cell-free systems that is based on the combination of a DNA aptamer that binds thrombin and the T7 bacteriophage promoter. Placement of the aptamer near the T7 promoter, and using a primarily single-stranded template, results in up to a 6-fold change in gene expression in a ligand concentration-dependent manner. We further demonstrate that the sensitivity to thrombin concentration and the fold change in expression can be tuned by altering the position of the aptamer. The results described here pave the way for the use of DNA aptamers to achieve modular regulation of transcription in response to a wide variety of ligands in cell-free systems.
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Affiliation(s)
- Sukanya Iyer
- Graduate
Program
in Genome Science and Technology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences
Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mitchel J. Doktycz
- Graduate
Program
in Genome Science and Technology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences
Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Center for
Nanophase
Materials Sciences, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
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26
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Xu L, Da L, Plouffe SW, Chong J, Kool E, Wang D. Molecular basis of transcriptional fidelity and DNA lesion-induced transcriptional mutagenesis. DNA Repair (Amst) 2014; 19:71-83. [PMID: 24767259 DOI: 10.1016/j.dnarep.2014.03.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Maintaining high transcriptional fidelity is essential for life. Some DNA lesions lead to significant changes in transcriptional fidelity. In this review, we will summarize recent progress towards understanding the molecular basis of RNA polymerase II (Pol II) transcriptional fidelity and DNA lesion-induced transcriptional mutagenesis. In particular, we will focus on the three key checkpoint steps of controlling Pol II transcriptional fidelity: insertion (specific nucleotide selection and incorporation), extension (differentiation of RNA transcript extension of a matched over mismatched 3'-RNA terminus), and proofreading (preferential removal of misincorporated nucleotides from the 3'-RNA end). We will also discuss some novel insights into the molecular basis and chemical perspectives of controlling Pol II transcriptional fidelity through structural, computational, and chemical biology approaches.
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Affiliation(s)
- Liang Xu
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California San Diego, La Jolla, CA 92093-0625, United States
| | - Linati Da
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California San Diego, La Jolla, CA 92093-0625, United States
| | - Steven W Plouffe
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California San Diego, La Jolla, CA 92093-0625, United States
| | - Jenny Chong
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California San Diego, La Jolla, CA 92093-0625, United States
| | - Eric Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305-5080, United States.
| | - Dong Wang
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California San Diego, La Jolla, CA 92093-0625, United States.
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27
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Tateishi-Karimata H, Isono N, Sugimoto N. New insights into transcription fidelity: thermal stability of non-canonical structures in template DNA regulates transcriptional arrest, pause, and slippage. PLoS One 2014; 9:e90580. [PMID: 24594642 PMCID: PMC3940900 DOI: 10.1371/journal.pone.0090580] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 02/04/2014] [Indexed: 11/25/2022] Open
Abstract
The thermal stability and topology of non-canonical structures of G-quadruplexes and hairpins in template DNA were investigated, and the effect of non-canonical structures on transcription fidelity was evaluated quantitatively. We designed ten template DNAs: A linear sequence that does not have significant higher-order structure, three sequences that form hairpin structures, and six sequences that form G-quadruplex structures with different stabilities. Templates with non-canonical structures induced the production of an arrested, a slipped, and a full-length transcript, whereas the linear sequence produced only a full-length transcript. The efficiency of production for run-off transcripts (full-length and slipped transcripts) from templates that formed the non-canonical structures was lower than that from the linear. G-quadruplex structures were more effective inhibitors of full-length product formation than were hairpin structure even when the stability of the G-quadruplex in an aqueous solution was the same as that of the hairpin. We considered that intra-polymerase conditions may differentially affect the stability of non-canonical structures. The values of transcription efficiencies of run-off or arrest transcripts were correlated with stabilities of non-canonical structures in the intra-polymerase condition mimicked by 20 wt% polyethylene glycol (PEG). Transcriptional arrest was induced when the stability of the G-quadruplex structure (−ΔGo37) in the presence of 20 wt% PEG was more than 8.2 kcal mol−1. Thus, values of stability in the presence of 20 wt% PEG are an important indicator of transcription perturbation. Our results further our understanding of the impact of template structure on the transcription process and may guide logical design of transcription-regulating drugs.
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Affiliation(s)
- Hisae Tateishi-Karimata
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, Kobe, Japan
| | - Noburu Isono
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, Kobe, Japan
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, Kobe, Japan
- Faculty of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, Kobe, Japan
- * E-mail:
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28
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Sugimoto N. Noncanonical structures and their thermodynamics of DNA and RNA under molecular crowding: beyond the Watson-Crick double helix. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 307:205-73. [PMID: 24380597 DOI: 10.1016/b978-0-12-800046-5.00008-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
How does molecular crowding affect the stability of nucleic acid structures inside cells? Water is the major solvent component in living cells, and the properties of water in the highly crowded media inside cells differ from that in buffered solution. As it is difficult to measure the thermodynamic behavior of nucleic acids in cells directly and quantitatively, we recently developed a cell-mimicking system using cosolutes as crowding reagents. The influences of molecular crowding on the structures and thermodynamics of various nucleic acid sequences have been reported. In this chapter, we discuss how the structures and thermodynamic properties of nucleic acids differ under various conditions such as highly crowded environments, compartment environments, and in the presence of ionic liquids, and the major determinants of the crowding effects on nucleic acids are discussed. The effects of molecular crowding on the activities of ribozymes and riboswitches on noncanonical structures of DNA- and RNA-like quadruplexes that play important roles in transcription and translation are also described.
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Affiliation(s)
- Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER) and Faculty of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, Kobe, Japan.
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29
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Belotserkovskii BP, Mirkin SM, Hanawalt PC. DNA sequences that interfere with transcription: implications for genome function and stability. Chem Rev 2013; 113:8620-37. [PMID: 23972098 DOI: 10.1021/cr400078y] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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30
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Oberstrass FC, Fernandes LE, Lebel P, Bryant Z. Torque spectroscopy of DNA: base-pair stability, boundary effects, backbending, and breathing dynamics. PHYSICAL REVIEW LETTERS 2013; 110:178103. [PMID: 23679785 PMCID: PMC3696636 DOI: 10.1103/physrevlett.110.178103] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Indexed: 05/16/2023]
Abstract
Changes in global DNA linking number can be accommodated by localized changes in helical structure. We have used single-molecule torque measurements to investigate sequence-specific strand separation and Z-DNA formation. By controlling the boundary conditions at the edges of sequences of interest, we have confirmed theoretical predictions of distinctive boundary-dependent backbending patterns in torque-twist relationships. Abrupt torque jumps are associated with the formation and collapse of DNA bubbles, permitting direct observations of DNA breathing dynamics.
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Affiliation(s)
| | | | - Paul Lebel
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
| | - Zev Bryant
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Structural Biology, Stanford University Medical Center, Stanford, CA 94305, USA
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31
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Vasquez KM, Wang G. The yin and yang of repair mechanisms in DNA structure-induced genetic instability. Mutat Res 2013; 743-744:118-131. [PMID: 23219604 PMCID: PMC3661696 DOI: 10.1016/j.mrfmmm.2012.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 11/21/2012] [Accepted: 11/24/2012] [Indexed: 01/14/2023]
Abstract
DNA can adopt a variety of secondary structures that deviate from the canonical Watson-Crick B-DNA form. More than 10 types of non-canonical or non-B DNA secondary structures have been characterized, and the sequences that have the capacity to adopt such structures are very abundant in the human genome. Non-B DNA structures have been implicated in many important biological processes and can serve as sources of genetic instability, implicating them in disease and evolution. Non-B DNA conformations interact with a wide variety of proteins involved in replication, transcription, DNA repair, and chromatin architectural regulation. In this review, we will focus on the interactions of DNA repair proteins with non-B DNA and their roles in genetic instability, as the proteins and DNA involved in such interactions may represent plausible targets for selective therapeutic intervention.
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Affiliation(s)
- Karen M Vasquez
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd. R1800, Austin, TX 78723, United States.
| | - Guliang Wang
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd. R1800, Austin, TX 78723, United States
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32
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Belotserkovskii BP, Neil AJ, Saleh SS, Shin JHS, Mirkin SM, Hanawalt PC. Transcription blockage by homopurine DNA sequences: role of sequence composition and single-strand breaks. Nucleic Acids Res 2012; 41:1817-28. [PMID: 23275544 PMCID: PMC3561996 DOI: 10.1093/nar/gks1333] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The ability of DNA to adopt non-canonical structures can affect transcription and has broad implications for genome functioning. We have recently reported that guanine-rich (G-rich) homopurine-homopyrimidine sequences cause significant blockage of transcription in vitro in a strictly orientation-dependent manner: when the G-rich strand serves as the non-template strand [Belotserkovskii et al. (2010) Mechanisms and implications of transcription blockage by guanine-rich DNA sequences., Proc. Natl Acad. Sci. USA, 107, 12816–12821]. We have now systematically studied the effect of the sequence composition and single-stranded breaks on this blockage. Although substitution of guanine by any other base reduced the blockage, cytosine and thymine reduced the blockage more significantly than adenine substitutions, affirming the importance of both G-richness and the homopurine-homopyrimidine character of the sequence for this effect. A single-strand break in the non-template strand adjacent to the G-rich stretch dramatically increased the blockage. Breaks in the non-template strand result in much weaker blockage signals extending downstream from the break even in the absence of the G-rich stretch. Our combined data support the notion that transcription blockage at homopurine-homopyrimidine sequences is caused by R-loop formation.
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33
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Lin Y, Wilson JH. Nucleotide excision repair, mismatch repair, and R-loops modulate convergent transcription-induced cell death and repeat instability. PLoS One 2012; 7:e46807. [PMID: 23056461 PMCID: PMC3463551 DOI: 10.1371/journal.pone.0046807] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 09/07/2012] [Indexed: 11/21/2022] Open
Abstract
Expansion of CAG•CTG tracts located in specific genes is responsible for 13 human neurodegenerative disorders, the pathogenic mechanisms of which are not yet well defined. These disease genes are ubiquitously expressed in human tissues, and transcription has been identified as one of the major pathways destabilizing the repeats. Transcription-induced repeat instability depends on transcription-coupled nucleotide excision repair (TC-NER), the mismatch repair (MMR) recognition component MSH2/MSH3, and RNA/DNA hybrids (R-loops). Recently, we reported that simultaneous sense and antisense transcription–convergent transcription–through a CAG repeat not only promotes repeat instability, but also induces a cell stress response, which arrests the cell cycle and eventually leads to massive cell death via apoptosis. Here, we use siRNA knockdowns to investigate whether NER, MMR, and R-loops also modulate convergent-transcription-induced cell death and repeat instability. We find that siRNA-mediated depletion of TC-NER components increases convergent transcription-induced cell death, as does the simultaneous depletion of RNase H1 and RNase H2A. In contrast, depletion of MSH2 decreases cell death. These results identify TC-NER, MMR recognition, and R-loops as modulators of convergent transcription-induced cell death and shed light on the molecular mechanism involved. We also find that the TC-NER pathway, MSH2, and R-loops modulate convergent transcription-induced repeat instability. These observations link the mechanisms of convergent transcription-induced repeat instability and convergent transcription-induced cell death, suggesting that a common structure may trigger both outcomes.
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Affiliation(s)
- Yunfu Lin
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas,United States of America
| | - John H. Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas,United States of America
- * E-mail:
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34
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Affiliation(s)
- Phil Hanawalt
- Department of Biology, Stanford University, California, United States.
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35
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Torque measurements reveal sequence-specific cooperative transitions in supercoiled DNA. Proc Natl Acad Sci U S A 2012; 109:6106-11. [PMID: 22474350 DOI: 10.1073/pnas.1113532109] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
B-DNA becomes unstable under superhelical stress and is able to adopt a wide range of alternative conformations including strand-separated DNA and Z-DNA. Localized sequence-dependent structural transitions are important for the regulation of biological processes such as DNA replication and transcription. To directly probe the effect of sequence on structural transitions driven by torque, we have measured the torsional response of a panel of DNA sequences using single molecule assays that employ nanosphere rotational probes to achieve high torque resolution. The responses of Z-forming d(pGpC)(n) sequences match our predictions based on a theoretical treatment of cooperative transitions in helical polymers. "Bubble" templates containing 50-100 bp mismatch regions show cooperative structural transitions similar to B-DNA, although less torque is required to disrupt strand-strand interactions. Our mechanical measurements, including direct characterization of the torsional rigidity of strand-separated DNA, establish a framework for quantitative predictions of the complex torsional response of arbitrary sequences in their biological context.
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Taira S, Osaka I, Shimma S, Kaneko D, Hiroki T, Kawamura-Konishi Y, Ichiyanagi Y. Oligonucleotide analysis by nanoparticle-assisted laser desorption/ionization mass spectrometry. Analyst 2012; 137:2006-10. [PMID: 22337326 DOI: 10.1039/c2an16237g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We analyzed oligonucleotides by nanoparticle-assisted laser desorption/ionization (nano-PALDI) mass spectrometry (MS). To this end, we prepared several kinds of nanoparticles (Cr-, Fe-, Mn-, Co-based) and optimized the nano-PALDI MS method to analyze the oligonucleotides. Iron oxide nanoparticles with diammonium hydrogen citrate were found to serve as an effective ionization-assisting reagent in MS. The mass spectra showed both [M - H](-) and [M + xMe(2+)- H](-) (Me: transition metal) peaks. The number of metal-adducted ion signals depended on the length of the oligonucleotide. This phenomenon was only observed using bivalent metal core nanoparticles, not with any other valency metal core nanoparticles. Our pilot study demonstrated that iron oxide nanoparticles could easily ionize samples such as chemical drugs and peptides as well as oligonucleotides without the aid of an oligonucleotide-specific chemical matrix (e.g., 3-hydroxypicolinic acid) used in conventional MS methods. These results suggested that iron-based nanoparticles may serve as the assisting material of ionization for genes and other biomolecules.
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Affiliation(s)
- Shu Taira
- Japan Advanced Institute of Science and Technology, School of Material Science, 1-1 Asahidai, Nomi City, Ishikawa 923-1292, Japan.
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Holmes AE, Choi JK, Francis J, D'Urso A, Balaz M. Sulfonated Ni(II)porphyrin improves the detection of Z-DNA in condensed and non-condensed BZB DNA sequences. J Inorg Biochem 2012; 110:18-20. [PMID: 22459169 DOI: 10.1016/j.jinorgbio.2012.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/31/2012] [Accepted: 02/01/2012] [Indexed: 11/26/2022]
Abstract
We report a very selective and sensitive spectroscopic detection of Z-DNA embedded in B-DNA in condensed as well as non-condensed DNA using anionic Ni(II) meso-tetrakis(4-sulphonatophenyl)porphyrin, NiTPPS. A combination of micromolar concentrations of Ni(II) and spermine(4+) allowed us to prepare left-handed Z-DNA in short oligonucleotides without DNA condensation. A strong induced circular dichroism (ICD) signal was observed in the visible absorption region when NiTPPS was added to BZ DNA (Z-DNA fragment located at the end of a B-DNA tract with one B/Z DNA junction) and BZB DNA (Z-DNA sequence embedded in B-DNA having two B/Z DNA junctions). Almost no ICD signal was detected when NiTPPS was added to B-DNA. NiTPPS showed different binding modes with condensed and non-condensed Z-DNAs and allowed the distinction between condensed Z-DNA (positive bisignate CD couplet) and non-condensed Z-DNA (negative bisignate CD couplet).
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Affiliation(s)
- Andrea E Holmes
- Department of Chemistry, Doane College, 1014 Boswell Ave, Crete, NE 68333, USA
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Choi JK, Sargsyan G, Shabbir-Hussain M, Holmes AE, Balaz M. Chiroptical detection of condensed nickel(II)-Z-DNA in the presence of the B-DNA via porphyrin exciton coupled circular dichroism. J Phys Chem B 2011; 115:10182-8. [PMID: 21774503 DOI: 10.1021/jp2047213] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here, we report a highly sensitive and specific chiroptical detection method of condensed left-handed Z-DNA in the presence of canonical right-handed B-DNA. The selective formation of a left-handed cytosine-guanine oligonucleotide (CG ODN) in the presence of a right-handed adenine-thymine oligonucleotide (AT ODN) was induced by millimolar concentrations of NiCl(2) and confirmed by electronic circular dichroism. The nickel(II) induced B- to Z-DNA transition of the CG ODN was accompanied by the concurrent condensation of the Ni(II)-Z-DNA, as confirmed by resonance light scattering, transmission spectroscopy, and centrifugation. The selective condensation of the CG ODN allowed its separation from the AT ODN using centrifugation. No structural changes were observed for the AT ODN upon addition of Ni(II). Anionic nickel(II) meso-tetra(4-sulfonatophenyl) porphyrin (NiTPPS) spectroscopically detected the left-handed Z-DNA in the Z-DNA/B-DNA mixture via a strong exciton coupled circular dichroism (ECCD) signal induced in the porphyrin Soret band absorption region. The bisignate ECCD signal originates from the assembly of achiral porphyrins into helical arrays by intermolecular interactions with the condensed Z-DNA scaffold. No induced CD signal was observed for the Ni(II)-B-DNA-NiTPPS complex. Hence, an unambiguous spectroscopic recognition of Ni(II) induced condensed Z-DNA in the presence of B-DNA is possible. The sensitivity of this chiroptical method was as low as 5% of the Z-DNA (4.4 μmol base pair concentration) in the presence of 95% B-DNA (80 μmol). Thus, NiTPPS is a highly sensitive probe for applications in biosensing via the CD signal amplification.
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Affiliation(s)
- Jung Kyu Choi
- Department of Chemistry, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, USA
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Salinas-Rios V, Belotserkovskii BP, Hanawalt PC. DNA slip-outs cause RNA polymerase II arrest in vitro: potential implications for genetic instability. Nucleic Acids Res 2011; 39:7444-54. [PMID: 21666257 PMCID: PMC3177194 DOI: 10.1093/nar/gkr429] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The abnormal number of repeats found in triplet repeat diseases arises from 'repeat instability', in which the repetitive section of DNA is subject to a change in copy number. Recent studies implicate transcription in a mechanism for repeat instability proposed to involve RNA polymerase II (RNAPII) arrest caused by a CTG slip-out, triggering transcription-coupled repair (TCR), futile cycles of which may lead to repeat expansion or contraction. In the present study, we use defined DNA constructs to directly test whether the structures formed by CAG and CTG repeat slip-outs can cause transcription arrest in vitro. We found that a slip-out of (CAG)(20) or (CTG)(20) repeats on either strand causes RNAPII arrest in HeLa cell nuclear extracts. Perfect hairpins and loops on either strand also cause RNAPII arrest. These findings are consistent with a transcription-induced repeat instability model in which transcription arrest in mammalian cells may initiate a 'gratuitous' TCR event leading to a change in repeat copy number. An understanding of the underlying mechanism of repeat instability could lead to intervention to slow down expansion and delay the onset of many neurodegenerative diseases in which triplet repeat expansion is implicated.
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Bacolla A, Wang G, Jain A, Chuzhanova NA, Cer RZ, Collins JR, Cooper DN, Bohr VA, Vasquez KM. Non-B DNA-forming sequences and WRN deficiency independently increase the frequency of base substitution in human cells. J Biol Chem 2011; 286:10017-26. [PMID: 21285356 PMCID: PMC3060453 DOI: 10.1074/jbc.m110.176636] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 01/31/2011] [Indexed: 01/01/2023] Open
Abstract
Although alternative DNA secondary structures (non-B DNA) can induce genomic rearrangements, their associated mutational spectra remain largely unknown. The helicase activity of WRN, which is absent in the human progeroid Werner syndrome, is thought to counteract this genomic instability. We determined non-B DNA-induced mutation frequencies and spectra in human U2OS osteosarcoma cells and assessed the role of WRN in isogenic knockdown (WRN-KD) cells using a supF gene mutation reporter system flanked by triplex- or Z-DNA-forming sequences. Although both non-B DNA and WRN-KD served to increase the mutation frequency, the increase afforded by WRN-KD was independent of DNA structure despite the fact that purified WRN helicase was found to resolve these structures in vitro. In U2OS cells, ∼70% of mutations comprised single-base substitutions, mostly at G·C base-pairs, with the remaining ∼30% being microdeletions. The number of mutations at G·C base-pairs in the context of NGNN/NNCN sequences correlated well with predicted free energies of base stacking and ionization potentials, suggesting a possible origin via oxidation reactions involving electron loss and subsequent electron transfer (hole migration) between neighboring bases. A set of ∼40,000 somatic mutations at G·C base pairs identified in a lung cancer genome exhibited similar correlations, implying that hole migration may also be involved. We conclude that alternative DNA conformations, WRN deficiency and lung tumorigenesis may all serve to increase the mutation rate by promoting, through diverse pathways, oxidation reactions that perturb the electron orbitals of neighboring bases. It follows that such "hole migration" is likely to play a much more widespread role in mutagenesis than previously anticipated.
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Affiliation(s)
- Albino Bacolla
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
| | - Guliang Wang
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
| | - Aklank Jain
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
| | - Nadia A. Chuzhanova
- the School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, United Kingdom
| | - Regina Z. Cer
- the Advanced Biomedical Computing Center, SAIC-Frederick, Inc., NCI-Frederick, Frederick, Maryland 21702
| | - Jack R. Collins
- the Advanced Biomedical Computing Center, SAIC-Frederick, Inc., NCI-Frederick, Frederick, Maryland 21702
| | - David N. Cooper
- the Institute of Medical Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom, and
| | - Vilhelm A. Bohr
- the Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224
| | - Karen M. Vasquez
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
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Convergent transcription through a long CAG tract destabilizes repeats and induces apoptosis. Mol Cell Biol 2010; 30:4435-51. [PMID: 20647539 DOI: 10.1128/mcb.00332-10] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Short repetitive sequences are common in the human genome, and many fall within transcription units. We have previously shown that transcription through CAG repeat tracts destabilizes them in a way that depends on transcription-coupled nucleotide excision repair and mismatch repair. Recent observations that antisense transcription accompanies sense transcription in many human genes led us to test the effects of antisense transcription on triplet repeat instability in human cells. Here, we report that simultaneous sense and antisense transcription (convergent transcription) initiated from two inducible promoters flanking a CAG95 tract in a nonessential gene enhances repeat instability synergistically, arrests the cell cycle, and causes massive cell death via apoptosis. Using chemical inhibitors and small interfering RNA (siRNA) knockdowns, we identified the ATR (ataxia-telangiectasia mutated [ATM] and Rad3 related) signaling pathway as a key mediator of this cellular response. RNA polymerase II, replication protein A (RPA), and components of the ATR signaling pathway accumulate at convergently transcribed repeat tracts, accompanied by phosphorylation of ATR, CHK1, and p53. Cell death depends on simultaneous sense and antisense transcription and is proportional to their relative levels, it requires the presence of the repeat tract, and it occurs in both proliferating and nonproliferating cells. Convergent transcription through a CAG repeat represents a novel mechanism for triggering a cellular stress response, one that is initiated by events at a single locus in the genome and resembles the response to DNA damage.
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Mechanisms and implications of transcription blockage by guanine-rich DNA sequences. Proc Natl Acad Sci U S A 2010; 107:12816-21. [PMID: 20616059 DOI: 10.1073/pnas.1007580107] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Various DNA sequences that interfere with transcription due to their unusual structural properties have been implicated in the regulation of gene expression and with genomic instability. An important example is sequences containing G-rich homopurine-homopyrimidine stretches, for which unusual transcriptional behavior is implicated in regulation of immunogenesis and in other processes such as genomic translocations and telomere function. To elucidate the mechanism of the effect of these sequences on transcription we have studied T7 RNA polymerase transcription of G-rich sequences in vitro. We have shown that these sequences produce significant transcription blockage in an orientation-, length- and supercoiling-dependent manner. Based upon the effects of various sequence modifications, solution conditions, and ribonucleotide substitutions, we conclude that transcription blockage is due to formation of unusually stable RNA/DNA hybrids, which could be further exacerbated by triplex formation. These structures are likely responsible for transcription-dependent replication blockage by G-rich sequences in vivo.
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Recognition of left-handed Z-DNA of short unmodified oligonucleotides under physiological ionic strength conditions. Biochem Biophys Res Commun 2010; 397:329-32. [PMID: 20510880 DOI: 10.1016/j.bbrc.2010.05.119] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 05/24/2010] [Indexed: 11/20/2022]
Abstract
The left-handed Z-DNA form of the short unmodified alternating guanine-cytosine oligonucleotides, 5'-(dGdC)(24) and 5'-(dGdC)(18), was selectively detected under physiological ionic strength and pH conditions using the anionic nickel(II) porphyrin, NiTPPS. No spectroscopic signal was observed for NiTPPS with any right-handed oligonucleotides under identical conditions. The 48mer 5'-(dGdC)(24) Z-form was detected at concentrations as low as 100nM. The binding of NiTPPS to the B- and Z-oligonucleotides was studied quantitatively by UV-vis absorption and circular dichroism spectroscopies. NiTPPS was found to be a universal DNA binder, with binding affinity and geometry depending on the ionic composition of the solution, rather than on the DNA helical twist. This is the first example of a successful spectroscopic detection of the Z-DNA of short unmodified oligonucleotides under physiological pH and ionic strength conditions.
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Banerjee A, Sammarco MC, Ditch S, Wang J, Grabczyk E. A novel tandem reporter quantifies RNA polymerase II termination in mammalian cells. PLoS One 2009; 4:e6193. [PMID: 19587781 PMCID: PMC2702688 DOI: 10.1371/journal.pone.0006193] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 06/15/2009] [Indexed: 12/05/2022] Open
Abstract
Background Making the correct choice between transcription elongation and transcription termination is essential to the function of RNA polymerase II, and fundamental to gene expression. This choice can be influenced by factors modifying the transcription complex, factors modifying chromatin, or signals mediated by the template or transcript. To aid in the study of transcription elongation and termination we have developed a transcription elongation reporter system that consists of tandem luciferase reporters flanking a test sequence of interest. The ratio of expression from the reporters provides a measure of the relative rates of successful elongation through the intervening sequence. Methodology/Principal Findings Size matched fragments containing the polyadenylation signal of the human β-actin gene (ACTB) and the human β-globin gene (HBB) were evaluated for transcription termination using this new ratiometric tandem reporter assay. Constructs bearing just 200 base pairs on either side of the consensus poly(A) addition site terminated 98% and 86% of transcription for ACTB and HBB sequences, respectively. The nearly 10-fold difference in read-through transcription between the two short poly(A) regions was eclipsed when additional downstream poly(A) sequence was included for each gene. Both poly(A) regions proved very effective at termination when 1100 base pairs were included, stopping 99.6% of transcription. To determine if part of the increased termination was simply due to the increased template length, we inserted several kilobases of heterologous coding sequence downstream of each poly(A) region test fragment. Unexpectedly, the additional length reduced the effectiveness of termination of HBB sequences 2-fold and of ACTB sequences 3- to 5-fold. Conclusions/Significance The tandem construct provides a sensitive measure of transcription termination in human cells. Decreased Xrn2 or Senataxin levels produced only a modest release from termination. Our data support overlap in allosteric and torpedo mechanisms of transcription termination and suggest that efficient termination is ensured by redundancy.
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Affiliation(s)
- Ayan Banerjee
- The Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Mimi C. Sammarco
- The Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Scott Ditch
- The Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Jeffrey Wang
- The Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Ed Grabczyk
- The Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- * E-mail:
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Belotserkovskii BP, Liu R, Hanawalt PC. Peptide nucleic acid (PNA) binding and its effect on in vitro transcription in friedreich's ataxia triplet repeats. Mol Carcinog 2009; 48:299-308. [PMID: 19306309 DOI: 10.1002/mc.20486] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Peptide nucleic acids (PNAs) are DNA mimics in which peptide-like linkages are substituted for the phosphodiester backbone. Homopyrimidine PNAs can invade double-stranded DNA containing the homologous sequence by displacing the homopyrimidine strand from the DNA duplex and forming a PNA/DNA/PNA triplex with the complementary homopurine strand. Among biologically interesting targets for triplex-forming PNA are (GAA/CTT)(n) repeats. Expansion of these repeats results in partial inhibition of transcription in the frataxin gene, causing Friedreich's ataxia. We have studied PNA binding and its effect on T7 RNA polymerase transcription in vitro for short repeats (n = 3) and for long repeats (n = 39), placed in both possible orientations relative to the T7 promoter such that either the GAA-strand, or the CTT-strand serves as the template for transcription. In all cases PNA bound specifically and efficiently to its target sequence. For the short insert, PNA binding to the template strand caused partial transcription blockage with well-defined sites of RNA product truncation in the region of the PNA-binding sequence, whereas binding to the nontemplate strand did not block transcription. However, PNA binding to long repeats, whether in the template or the nontemplate strand, resulted in a dramatic reduction of the amount of full-length transcription product, although in the case of the nontemplate strand there were no predominant truncation sites. Biological implications of these results are discussed.
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Bétous R, Rey L, Wang G, Pillaire MJ, Puget N, Selves J, Biard DSF, Shin-ya K, Vasquez KM, Cazaux C, Hoffmann JS. Role of TLS DNA polymerases eta and kappa in processing naturally occurring structured DNA in human cells. Mol Carcinog 2009; 48:369-78. [PMID: 19117014 DOI: 10.1002/mc.20509] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Accurate DNA replication during S-phase is fundamental to maintain genome integrity. During this critical process, replication forks frequently encounter obstacles that impede their progression. While the regulatory pathways which act in response to exogenous replication stress are beginning to emerge, the mechanisms by which fork integrity is maintained at naturally occurring endogenous replication-impeding sequences remains obscure. Notably, little is known about how cells replicate through special chromosomal regions containing structured non-B DNA, for example, G4 quartets, known to hamper fork progression or trigger chromosomal rearrangements. Here, we have investigated the role in this process of the human translesion synthesis (TLS) DNA polymerases of the Y-family (pol eta, pol iota, and pol kappa), specialized enzymes known to synthesize DNA through DNA damage. We show that depletion by RNA interference of expression of the genes for Pol eta or Pol kappa, but not Pol iota, sensitizes U2OS cells treated with the G4-tetraplex interactive compound telomestatin and triggers double-strand breaks in HeLa cells harboring multiple copies of a G-rich sequence from the promoter region of the human c-MYC gene, chromosomally integrated as a transgene. Moreover, we found that downregulation of Pol kappa only raises the level of DSB in HeLa cells containing either one of two breakage hotspot structured DNA sequences in the chromosome, the major break region (Mbr) of BCL-2 gene and the GA rich region from the far right-hand end of the genome of the Kaposi Sarcoma associated Herpesvirus. These data suggest that naturally occurring DNA structures are physiological substrates of both pol eta and pol kappa. We discuss these data in the light of their downregulation in human cancers.
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Affiliation(s)
- Rémy Bétous
- CNRS, Institute of Pharmacology and Structural Biology (IPBS), Toulouse, France
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Abstract
Triplet repeat expansion is the molecular basis for several human diseases. Intensive studies using systems in bacteria, yeast, flies, mammalian cells, and mice have provided important insights into the molecular processes that are responsible for mediating repeat instability. The age-dependent, ongoing repeat instability in somatic tissues, especially in terminally differentiated neurons, strongly suggests a robust role for pathways that are independent of DNA replication. Several genetic studies have indicated that transcription can play a critical role in repeat instability, potentially providing a basis for the instability observed in neurons. Transcription-induced repeat instability can be modulated by several DNA repair proteins, including those involved in mismatch repair (MMR) and transcription-coupled nucleotide excision repair (TC-NER). Though the mechanism is unclear, it is likely that transcription facilitates the formation of repeat-specific secondary structures, which act as intermediates to trigger DNA repair, eventually leading to changes in the length of the repeat tract. In addition, other processes associated with transcription can also modulate repeat instability, as shown in a variety of different systems. Overall, the mechanisms underlying repeat instability in humans are unexpectedly complicated. Because repeat-disease genes are widely expressed, transcription undoubtedly contributes to the repeat instability observed in many diseases, but it may be especially important in nondividing cells. Transcription-induced instability is likely to involve an extensive interplay not only of the core transcription machinery and DNA repair proteins, but also of proteins involved in chromatin remodeling, regulation of supercoiling, and removal of stalled RNA polymerases, as well as local DNA sequence effects.
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Affiliation(s)
- Yunfu Lin
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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48
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Wang G, Vasquez KM. Models for chromosomal replication-independent non-B DNA structure-induced genetic instability. Mol Carcinog 2009; 48:286-98. [PMID: 19123200 PMCID: PMC2766916 DOI: 10.1002/mc.20508] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Regions of genomic DNA containing repetitive nucleotide sequences can adopt a number of different structures in addition to the canonical B-DNA form: many of these non-B DNA structures are causative factors in genetic instability and human disease. Although chromosomal DNA replication through such repetitive sequences has been considered a major cause of non-B form DNA structure-induced genetic instability, it is also observed in non-proliferative tissues. In this review, we discuss putative mechanisms responsible for the mutagenesis induced by non-B DNA structures in the absence of chromosomal DNA replication.
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Affiliation(s)
- Guliang Wang
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
| | - Karen M. Vasquez
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
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50
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Transcription-coupled DNA repair: two decades of progress and surprises. Nat Rev Mol Cell Biol 2008; 9:958-70. [PMID: 19023283 DOI: 10.1038/nrm2549] [Citation(s) in RCA: 777] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Expressed genes are scanned by translocating RNA polymerases, which sensitively detect DNA damage and initiate transcription-coupled repair (TCR), a subpathway of nucleotide excision repair that removes lesions from the template DNA strands of actively transcribed genes. Human hereditary diseases that present a deficiency only in TCR are characterized by sunlight sensitivity without enhanced skin cancer. Although multiple gene products are implicated in TCR, we still lack an understanding of the precise signals that can trigger this pathway. Futile cycles of TCR at naturally occurring non-canonical DNA structures might contribute to genomic instability and genetic disease.
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