1
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McQuaid K, Pipier A, Cardin C, Monchaud D. Interactions of small molecules with DNA junctions. Nucleic Acids Res 2022; 50:12636-12656. [PMID: 36382400 PMCID: PMC9825177 DOI: 10.1093/nar/gkac1043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/13/2022] [Accepted: 10/23/2022] [Indexed: 11/17/2022] Open
Abstract
The four natural DNA bases (A, T, G and C) associate in base pairs (A=T and G≡C), allowing the attached DNA strands to assemble into the canonical double helix of DNA (or duplex-DNA, also known as B-DNA). The intrinsic supramolecular properties of nucleobases make other associations possible (such as base triplets or quartets), which thus translates into a diversity of DNA structures beyond B-DNA. To date, the alphabet of DNA structures is ripe with approximately 20 letters (from A- to Z-DNA); however, only a few of them are being considered as key players in cell biology and, by extension, valuable targets for chemical biology intervention. In the present review, we summarise what is known about alternative DNA structures (what are they? When, where and how do they fold?) and proceed to discuss further about those considered nowadays as valuable therapeutic targets. We discuss in more detail the molecular tools (ligands) that have been recently developed to target these structures, particularly the three- and four-way DNA junctions, in order to intervene in the biological processes where they are involved. This new and stimulating chemical biology playground allows for devising innovative strategies to fight against genetic diseases.
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Affiliation(s)
- Kane T McQuaid
- Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK
| | - Angélique Pipier
- Institut de Chimie Moléculaire de l’Université de Bourgogne (ICMUB), CNRS UMR 6302, UBFC Dijon, 21078 Dijon, France
| | - Christine J Cardin
- Correspondence may also be addressed to Christine J. Cardin. Tel: +44 118 378 8215;
| | - David Monchaud
- To whom correspondence should be addressed. Tel: +33 380 399 043;
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2
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Shi X, Teng H, Sun Z. An updated overview of experimental and computational approaches to identify non-canonical DNA/RNA structures with emphasis on G-quadruplexes and R-loops. Brief Bioinform 2022; 23:6751149. [PMID: 36208174 PMCID: PMC9677470 DOI: 10.1093/bib/bbac441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 08/22/2022] [Accepted: 09/13/2022] [Indexed: 12/14/2022] Open
Abstract
Multiple types of non-canonical nucleic acid structures play essential roles in DNA recombination and replication, transcription, and genomic instability and have been associated with several human diseases. Thus, an increasing number of experimental and bioinformatics methods have been developed to identify these structures. To date, most reviews have focused on the features of non-canonical DNA/RNA structure formation, experimental approaches to mapping these structures, and the association of these structures with diseases. In addition, two reviews of computational algorithms for the prediction of non-canonical nucleic acid structures have been published. One of these reviews focused only on computational approaches for G4 detection until 2020. The other mainly summarized the computational tools for predicting cruciform, H-DNA and Z-DNA, in which the algorithms discussed were published before 2012. Since then, several experimental and computational methods have been developed. However, a systematic review including the conformation, sequencing mapping methods and computational prediction strategies for these structures has not yet been published. The purpose of this review is to provide an updated overview of conformation, current sequencing technologies and computational identification methods for non-canonical nucleic acid structures, as well as their strengths and weaknesses. We expect that this review will aid in understanding how these structures are characterised and how they contribute to related biological processes and diseases.
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Affiliation(s)
- Xiaohui Shi
- Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, The first Affiliated Hospital of WMU; Beijing Institutes of Life Science, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Ouhai District, Wenzhou 325000, China
| | - Huajing Teng
- Department of Radiation Oncology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education) at Peking University Cancer Hospital and Institute, Ouhai District, Wenzhou 325000, China
| | - Zhongsheng Sun
- Corresponding author: Zhongsheng Sun, Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, The 1st Affiliated Hospital of WMU, Nanbaixiang Wenyi Yiyuan Xinyuan District, Ouhai District, Wenzhou 325000, China. E-mail:
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3
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Structural switching/polymorphism by sequential base substitution at quasi-palindromic SNP site (G → A) in LCR of human β-globin gene cluster. Int J Biol Macromol 2021; 201:216-225. [PMID: 34973267 DOI: 10.1016/j.ijbiomac.2021.12.142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 12/21/2021] [Accepted: 12/21/2021] [Indexed: 11/20/2022]
Abstract
The human β-globin gene Locus Control Region (LCR), a dominant regulator of globin gene expression contains five tissue-specific DNase I-hypersensitive sites (HSs). A single nucleotide polymorphism (SNP) (A → G) present in HS4 region of locus control region (LCR), have shown a notable association between the G allele and the occurrence of β-thalassemia. This SNP site exhibiting a hairpin - duplex equilibrium manifested in A → B like DNA transition has previously been reported from this laboratory. Since, DNA is a dynamic and adaptable molecule, so any change of a single base within a primary DNA sequence can produce major biological consequences commonly manifested in genetic disorders such as sickle cell anemia and β-thalassemia. Herein, the differential behavior of sequential single base substitutions G → A on the quasi-palindromic sequence (d-TGGGGGCCCCA; HPG11) has been explored. A combination of native gel electrophoresis, circular dichroism (CD), and UV-thermal denaturation (Tm) techniques have been used to investigate the structural polymorphism associated with various variants of HPG11 i.e. HPG11A2 to HPG11A5. The CD spectra confirmed that all the HPG11 variants exhibit a hairpin - duplex equilibrium. Oligomer concentration dependence on CD spectra has been correlated with A → B DNA conformational transition. However, as revealed in gel electrophoresis, HPG11A2 → A5 exhibit the formation of a tetramolecular structure (four-way junction) at higher oligomer concentration. UV-melting studies also supported the melting of hairpin, duplex and four-way junction structure. This polymorphism pattern may possibly be significant for DNA-protein recognition, in the process of regulation of LCR in the β-globin gene.
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4
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Protein innovation through template switching in the Saccharomyces cerevisiae lineage. Sci Rep 2021; 11:22558. [PMID: 34799587 PMCID: PMC8604942 DOI: 10.1038/s41598-021-01736-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 10/27/2021] [Indexed: 11/08/2022] Open
Abstract
DNA polymerase template switching between short, non-identical inverted repeats (IRs) is a genetic mechanism that leads to the homogenization of IR arms and to IR spacer inversion, which cause multinucleotide mutations (MNMs). It is unknown if and how template switching affects gene evolution. In this study, we performed a phylogenetic analysis to determine the effect of template switching between IR arms on coding DNA of Saccharomyces cerevisiae. To achieve this, perfect IRs that co-occurred with MNMs between a strain and its parental node were identified in S. cerevisiae strains. We determined that template switching introduced MNMs into 39 protein-coding genes through S. cerevisiae evolution, resulting in both arm homogenization and inversion of the IR spacer. These events in turn resulted in nonsynonymous substitutions and up to five neighboring amino acid replacements in a single gene. The study demonstrates that template switching is a powerful generator of multiple substitutions within codons. Additionally, some template switching events occurred more than once during S. cerevisiae evolution. Our findings suggest that template switching constitutes a general mutagenic mechanism that results in both nonsynonymous substitutions and parallel evolution, which are traditionally considered as evidence for positive selection, without the need for adaptive explanations.
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5
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Javadekar SM, Nilavar NM, Paranjape A, Das K, Raghavan SC. Characterization of G-quadruplex antibody reveals differential specificity for G4 DNA forms. DNA Res 2021; 27:5934508. [PMID: 33084858 PMCID: PMC7711166 DOI: 10.1093/dnares/dsaa024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 10/08/2020] [Indexed: 12/11/2022] Open
Abstract
Accumulating evidence suggests that human genome can fold into non-B DNA structures, when appropriate sequence and favourable conditions are present. Among these, G-quadruplexes (G4-DNA) are associated with gene regulation, chromosome fragility and telomere maintenance. Although several techniques are used in detecting such structures in vitro, understanding their intracellular existence has been challenging. Recently, an antibody, BG4, was described to study G4 structures within cells. Here, we characterize BG4 for its affinity towards G4-DNA, using several biochemical and biophysical tools. BG4 bound to G-rich DNA derived from multiple genes that form G-quadruplexes, unlike complementary C-rich or random sequences. BLI studies revealed robust binding affinity (Kd = 17.4 nM). Gel shift assays show BG4 binds to inter- and intramolecular G4-DNA, when it is in parallel orientation. Mere presence of G4-motif in duplex DNA is insufficient for antibody recognition. Importantly, BG4 can bind to G4-DNA within telomere sequence in a supercoiled plasmid. Finally, we show that BG4 binds to form efficient foci in four cell lines, irrespective of their lineage, demonstrating presence of G4-DNA in genome. Importantly, number of BG4 foci within the cells can be modulated, upon knockdown of G4-resolvase, WRN. Thus, we establish specificity of BG4 towards G4-DNA and discuss its potential applications.
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Affiliation(s)
- Saniya M Javadekar
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Namrata M Nilavar
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Amita Paranjape
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Kohal Das
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Sathees C Raghavan
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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6
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Svetec Miklenić M, Svetec IK. Palindromes in DNA-A Risk for Genome Stability and Implications in Cancer. Int J Mol Sci 2021; 22:2840. [PMID: 33799581 PMCID: PMC7999016 DOI: 10.3390/ijms22062840] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/04/2021] [Accepted: 03/08/2021] [Indexed: 02/07/2023] Open
Abstract
A palindrome in DNA consists of two closely spaced or adjacent inverted repeats. Certain palindromes have important biological functions as parts of various cis-acting elements and protein binding sites. However, many palindromes are known as fragile sites in the genome, sites prone to chromosome breakage which can lead to various genetic rearrangements or even cell death. The ability of certain palindromes to initiate genetic recombination lies in their ability to form secondary structures in DNA which can cause replication stalling and double-strand breaks. Given their recombinogenic nature, it is not surprising that palindromes in the human genome are involved in genetic rearrangements in cancer cells as well as other known recurrent translocations and deletions associated with certain syndromes in humans. Here, we bring an overview of current understanding and knowledge on molecular mechanisms of palindrome recombinogenicity and discuss possible implications of DNA palindromes in carcinogenesis. Furthermore, we overview the data on known palindromic sequences in the human genome and efforts to estimate their number and distribution, as well as underlying mechanisms of genetic rearrangements specific palindromic sequences cause.
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Affiliation(s)
| | - Ivan Krešimir Svetec
- Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia;
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7
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Zell J, Rota Sperti F, Britton S, Monchaud D. DNA folds threaten genetic stability and can be leveraged for chemotherapy. RSC Chem Biol 2021; 2:47-76. [PMID: 35340894 PMCID: PMC8885165 DOI: 10.1039/d0cb00151a] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 09/20/2020] [Indexed: 12/22/2022] Open
Abstract
Damaging DNA is a current and efficient strategy to fight against cancer cell proliferation. Numerous mechanisms exist to counteract DNA damage, collectively referred to as the DNA damage response (DDR) and which are commonly dysregulated in cancer cells. Precise knowledge of these mechanisms is necessary to optimise chemotherapeutic DNA targeting. New research on DDR has uncovered a series of promising therapeutic targets, proteins and nucleic acids, with application notably via an approach referred to as combination therapy or combinatorial synthetic lethality. In this review, we summarise the cornerstone discoveries which gave way to the DNA being considered as an anticancer target, and the manipulation of DDR pathways as a valuable anticancer strategy. We describe in detail the DDR signalling and repair pathways activated in response to DNA damage. We then summarise the current understanding of non-B DNA folds, such as G-quadruplexes and DNA junctions, when they are formed and why they can offer a more specific therapeutic target compared to that of canonical B-DNA. Finally, we merge these subjects to depict the new and highly promising chemotherapeutic strategy which combines enhanced-specificity DNA damaging and DDR targeting agents. This review thus highlights how chemical biology has given rise to significant scientific advances thanks to resolutely multidisciplinary research efforts combining molecular and cell biology, chemistry and biophysics. We aim to provide the non-specialist reader a gateway into this exciting field and the specialist reader with a new perspective on the latest results achieved and strategies devised.
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Affiliation(s)
- Joanna Zell
- Institut de Chimie Moléculaire de l'Université de Bourgogne, ICMUB CNRS UMR 6302, UBFC Dijon France
| | - Francesco Rota Sperti
- Institut de Chimie Moléculaire de l'Université de Bourgogne, ICMUB CNRS UMR 6302, UBFC Dijon France
| | - Sébastien Britton
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS Toulouse France
- Équipe Labellisée la Ligue Contre le Cancer 2018 Toulouse France
| | - David Monchaud
- Institut de Chimie Moléculaire de l'Université de Bourgogne, ICMUB CNRS UMR 6302, UBFC Dijon France
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8
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Čutová M, Manta J, Porubiaková O, Kaura P, Šťastný J, Jagelská EB, Goswami P, Bartas M, Brázda V. Divergent distributions of inverted repeats and G-quadruplex forming sequences in Saccharomyces cerevisiae. Genomics 2019; 112:1897-1901. [PMID: 31706022 DOI: 10.1016/j.ygeno.2019.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 09/13/2019] [Accepted: 11/01/2019] [Indexed: 12/17/2022]
Abstract
The importance of DNA structure in the regulation of basic cellular processes is an emerging field of research. Among local non-B DNA structures, inverted repeat (IR) sequences that form cruciforms and G-rich sequences that form G-quadruplexes (G4) are found in all prokaryotic and eukaryotic organisms and are targets for regulatory proteins. We analyzed IRs and G4 sequences in the genome of the most important biotechnology microorganism, S. cerevisiae. IR and G4-prone sequences are enriched in specific genomic locations and differ markedly between mitochondrial and nuclear DNA. While G4s are overrepresented in telomeres and regions surrounding tRNAs, IRs are most enriched in centromeres, rDNA, replication origins and surrounding tRNAs. Mitochondrial DNA is enriched in both IR and G4-prone sequences relative to the nuclear genome. This extensive analysis of local DNA structures adds to the emerging picture of their importance in genome maintenance, DNA replication and transcription of subsets of genes.
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Affiliation(s)
- Michaela Čutová
- Brno University of Technology, Faculty of Chemistry, Purkyňova 118, 612 00 Brno, Czech Republic
| | - Jacinta Manta
- Brno University of Technology, Faculty of Chemistry, Purkyňova 118, 612 00 Brno, Czech Republic
| | - Otília Porubiaková
- Brno University of Technology, Faculty of Chemistry, Purkyňova 118, 612 00 Brno, Czech Republic
| | - Patrik Kaura
- Brno University of Technology, Faculty of Mechanical Engineering, Technická 2896/2, 616 69 Brno, Czech Republic
| | - Jiří Šťastný
- Brno University of Technology, Faculty of Mechanical Engineering, Technická 2896/2, 616 69 Brno, Czech Republic; Mendel University in Brno, Zemědělská 1665/1, 61300 Brno, Czech Republic
| | - Eva B Jagelská
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Pratik Goswami
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Martin Bartas
- Department of Biology and Ecology/Institute of Environmental Technologies, Faculty of Science, University of Ostrava, Ostrava 710 00, Czech Republic
| | - Václav Brázda
- Brno University of Technology, Faculty of Chemistry, Purkyňova 118, 612 00 Brno, Czech Republic; Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic.
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9
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Shi J, Liang C. Generic Repeat Finder: A High-Sensitivity Tool for Genome-Wide De Novo Repeat Detection. PLANT PHYSIOLOGY 2019; 180:1803-1815. [PMID: 31152127 PMCID: PMC6670090 DOI: 10.1104/pp.19.00386] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 05/17/2019] [Indexed: 05/25/2023]
Abstract
Comprehensive and accurate annotation of the repeatome, including transposons, is critical for deepening our understanding of repeat origins, biogenesis, regulatory mechanisms, and roles. Here, we developed Generic Repeat Finder (GRF), a tool for genome-wide repeat detection based on fast, exhaustive numerical calculation algorithms integrated with optimized dynamic programming strategies. GRF sensitively identifies terminal inverted repeats (TIRs), terminal direct repeats (TDRs), and interspersed repeats that bear both inverted and direct repeats. GRF also detects DNA or RNA transposable elements characterized by these repeats in plant and animal genomes. For TIRs and TDRs, GRF identifies spacers in the middle and mismatches/insertions or deletions in terminal repeats, showing their alignment or base-pairing information. GRF helps improve the annotation for various DNA transposons and retrotransposons, such as miniature inverted-repeat transposable elements (MITEs), long terminal repeat (LTR) retrotransposons, and non-LTR retrotransposons, including long interspersed nuclear elements and short interspersed nuclear elements in plants. We used GRF to perform TIR/TDR, interspersed-repeat, and MITE detection in several species, including Arabidopsis (Arabidopsis thaliana), rice (Oryza sativa), and mouse (Mus musculus). As a generic bioinformatics tool in repeat finding implemented as a parallelized C++ program, GRF was faster and more sensitive than the existing inverted repeat/MITE detection tools based on numerical approaches (i.e. detectIR and detectMITE) in Arabidopsis and mouse. GRF is more sensitive than Inverted Repeat Finder in TIR detection, LTR_FINDER in short TDR detection (≤1,000 nt), and phRAIDER in interspersed repeat detection in Arabidopsis and rice. GRF is an open source available from Github.
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Affiliation(s)
- Jieming Shi
- Department of Biology, Miami University, Oxford, Ohio 45056
| | - Chun Liang
- Department of Biology, Miami University, Oxford, Ohio 45056
- Department of Computer Science and Software Engineering, Miami University, Oxford, Ohio 45056
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10
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Abstract
Background:
Although most nucleotides in the genome form canonical double-stranded
B-DNA, many repeated sequences transiently present as non-canonical conformations (non-B
DNA) such as triplexes, quadruplexes, Z-DNA, cruciforms, and slipped/hairpins. Those noncanonical
DNAs (ncDNAs) are not only associated with many genetic events such as replication,
transcription, and recombination, but are also related to the genetic instability that results in the
predisposition to disease. Due to the crucial roles of ncDNAs in cellular and genetic functions,
various computational methods have been implemented to predict sequence motifs that generate
ncDNA.
Objective:
Here, we review strategies for the identification of ncDNA motifs across the whole
genome, which is necessary for further understanding and investigation of the structure and
function of ncDNAs.
Conclusion:
There is a great demand for computational prediction of non-canonical DNAs that
play key functional roles in gene expression and genome biology. In this study, we review the
currently available computational methods for predicting the non-canonical DNAs in the genome.
Current studies not only provide an insight into the computational methods for predicting the
secondary structures of DNA but also increase our understanding of the roles of non-canonical
DNA in the genome.
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Affiliation(s)
- Nazia Parveen
- Department of Molecular Cell Biology, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Korea
| | - Amen Shamim
- Department of Molecular Cell Biology, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Korea
| | - Seunghee Cho
- Department of Molecular Cell Biology, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Korea
| | - Kyeong Kyu Kim
- Department of Molecular Cell Biology, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Korea
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Todd RT, Wikoff TD, Forche A, Selmecki A. Genome plasticity in Candida albicans is driven by long repeat sequences. eLife 2019; 8:45954. [PMID: 31172944 PMCID: PMC6591007 DOI: 10.7554/elife.45954] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 06/07/2019] [Indexed: 11/13/2022] Open
Abstract
Genome rearrangements resulting in copy number variation (CNV) and loss of heterozygosity (LOH) are frequently observed during the somatic evolution of cancer and promote rapid adaptation of fungi to novel environments. In the human fungal pathogen Candida albicans, CNV and LOH confer increased virulence and antifungal drug resistance, yet the mechanisms driving these rearrangements are not completely understood. Here, we unveil an extensive array of long repeat sequences (65-6499 bp) that are associated with CNV, LOH, and chromosomal inversions. Many of these long repeat sequences are uncharacterized and encompass one or more coding sequences that are actively transcribed. Repeats associated with genome rearrangements are predominantly inverted and separated by up to ~1.6 Mb, an extraordinary distance for homology-based DNA repair/recombination in yeast. These repeat sequences are a significant source of genome plasticity across diverse strain backgrounds including clinical, environmental, and experimentally evolved isolates, and represent previously uncharacterized variation in the reference genome.
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Affiliation(s)
- Robert T Todd
- Creighton University Medical School, Omaha, United States
| | - Tyler D Wikoff
- Creighton University Medical School, Omaha, United States
| | | | - Anna Selmecki
- Creighton University Medical School, Omaha, United States
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12
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Fan H, Wang J, Komiyama M, Liang X. Effects of secondary structures of DNA templates on the quantification of qPCR. J Biomol Struct Dyn 2019; 37:2867-2874. [PMID: 30101656 DOI: 10.1080/07391102.2018.1498804] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
In the current design of quantitative polymerase chain reaction (qPCR) systems, the sequences of primers are the primary concerns. The secondary structures of DNA templates have not been much considered, although they should be also critically important. In this paper, various hairpins with different stem lengths and loop sizes are placed near primer-binding sites, and their effects on the amplification efficiency of qPCR are systematically investigated. When a hairpin is formed either in the inside of the amplicon or in its outside, the amplification is notably suppressed. The magnitudes of suppression increase with the increase in stem length and the decrease in loop size, and are especially significant for the hairpins formed inside the amplicon. With very long stems (e.g., 20-bp), the effect is still more drastic, and no targeted amplification products are formed. On the basis of melting temperature (Tm) measurements, these suppression effects of hairpins have been mostly ascribed to competitive inhibition of primer binding to the template. It has been concluded that, in order to design precise and reliable qPCR systems, at least 60-bp sequences around primer-binding sites, both inside and outside the amplicons, must be analyzed to confirm that stable secondary structures are not formed in the vicinity of primer-binding sites. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Huijun Fan
- a College of Food Science and Engineering , Ocean University of China , Qingdao , China
| | - Jing Wang
- a College of Food Science and Engineering , Ocean University of China , Qingdao , China.,b Laboratory for Marine Drugs and Bioproducts , Qingdao National Laboratory for Marine Science and Technology , Qingdao , China
| | - Makoto Komiyama
- a College of Food Science and Engineering , Ocean University of China , Qingdao , China.,c National Institute for Materials Science (NIMS) , Tsukuba , Japan
| | - Xingguo Liang
- a College of Food Science and Engineering , Ocean University of China , Qingdao , China.,b Laboratory for Marine Drugs and Bioproducts , Qingdao National Laboratory for Marine Science and Technology , Qingdao , China
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13
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Miura O, Ogake T, Yoneyama H, Kikuchi Y, Ohyama T. A strong structural correlation between short inverted repeat sequences and the polyadenylation signal in yeast and nucleosome exclusion by these inverted repeats. Curr Genet 2018; 65:575-590. [PMID: 30498953 PMCID: PMC6420913 DOI: 10.1007/s00294-018-0907-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/14/2018] [Accepted: 11/15/2018] [Indexed: 11/22/2022]
Abstract
DNA sequences that read the same from 5′ to 3′ in either strand are called inverted repeat sequences or simply IRs. They are found throughout a wide variety of genomes, from prokaryotes to eukaryotes. Despite extensive research, their in vivo functions, if any, remain unclear. Using Saccharomyces cerevisiae, we performed genome-wide analyses for the distribution, occurrence frequency, sequence characteristics and relevance to chromatin structure, for the IRs that reportedly have a cruciform-forming potential. Here, we provide the first comprehensive map of these IRs in the S. cerevisiae genome. The statistically significant enrichment of the IRs was found in the close vicinity of the DNA positions corresponding to polyadenylation [poly(A)] sites and ~ 30 to ~ 60 bp downstream of start codon-coding sites (referred to as ‘start codons’). In the former, ApT- or TpA-rich IRs and A-tract- or T-tract-rich IRs are enriched, while in the latter, different IRs are enriched. Furthermore, we found a strong structural correlation between the former IRs and the poly(A) signal. In the chromatin formed on the gene end regions, the majority of the IRs causes low nucleosome occupancy. The IRs in the region ~ 30 to ~ 60 bp downstream of start codons are located in the + 1 nucleosomes. In contrast, fewer IRs are present in the adjacent region downstream of start codons. The current study suggests that the IRs play similar roles in Escherichia coli and S. cerevisiae to regulate or complete transcription at the RNA level.
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Affiliation(s)
- Osamu Miura
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Toshihiro Ogake
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Hiroki Yoneyama
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Yo Kikuchi
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Takashi Ohyama
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan. .,Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.
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14
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Lavi B, Levy Karin E, Pupko T, Hazkani-Covo E. The Prevalence and Evolutionary Conservation of Inverted Repeats in Proteobacteria. Genome Biol Evol 2018; 10:918-927. [PMID: 29608719 PMCID: PMC5941160 DOI: 10.1093/gbe/evy044] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2018] [Indexed: 12/11/2022] Open
Abstract
Perfect short inverted repeats (IRs) are known to be enriched in a variety of bacterial and eukaryotic genomes. Currently, it is unclear whether perfect IRs are conserved over evolutionary time scales. In this study, we aimed to characterize the prevalence and evolutionary conservation of IRs across 20 proteobacterial strains. We first identified IRs in Escherichia coli K-12 substr MG1655 and showed that they are overabundant. We next aimed to test whether this overabundance is reflected in the conservation of IRs over evolutionary time scales. To this end, for each perfect IR identified in E. coli MG1655, we collected orthologous sequences from related proteobacterial genomes. We next quantified the evolutionary conservation of these IRs, that is, the presence of the exact same IR across orthologous regions. We observed high conservation of perfect IRs: out of the 234 examined orthologous regions, 145 were more conserved than expected, which is statistically significant even after correcting for multiple testing. Our results together with previous experimental findings support a model in which imperfect IRs are corrected to perfect IRs in a preferential manner via a template switching mechanism.
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Affiliation(s)
- Bar Lavi
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Eli Levy Karin
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
- Department of Molecular Biology & Ecology of Plants, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Tal Pupko
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
| | - Einat Hazkani-Covo
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
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15
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Miura O, Ogake T, Ohyama T. Requirement or exclusion of inverted repeat sequences with cruciform-forming potential in Escherichia coli revealed by genome-wide analyses. Curr Genet 2018; 64:945-958. [PMID: 29484452 PMCID: PMC6060812 DOI: 10.1007/s00294-018-0815-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 02/16/2018] [Accepted: 02/19/2018] [Indexed: 12/31/2022]
Abstract
Inverted repeat (IR) sequences are DNA sequences that read the same from 5' to 3' in each strand. Some IRs can form cruciforms under the stress of negative supercoiling, and these IRs are widely found in genomes. However, their biological significance remains unclear. The aim of the current study is to explore this issue further. We constructed the first Escherichia coli genome-wide comprehensive map of IRs with cruciform-forming potential. Based on the map, we performed detailed and quantitative analyses. Here, we report that IRs with cruciform-forming potential are statistically enriched in the following five regions: the adjacent regions downstream of the stop codon-coding sites (referred to as the stop codons), on and around the positions corresponding to mRNA ends (referred to as the gene ends), ~ 20 to ~45 bp upstream of the start codon-coding sites (referred to as the start codons) within the 5'-UTR (untranslated region), ~ 25 to ~ 60 bp downstream of the start codons, and promoter regions. For the adjacent regions downstream of the stop codons and on and around the gene ends, most of the IRs with a repeat unit length of ≥ 8 bp and a spacer size of ≤ 8 bp were parts of the intrinsic terminators, regardless of the location, and presumably used for Rho-independent transcription termination. In contrast, fewer IRs were present in the small region preceding the start codons. In E. coli, IRs with cruciform-forming potential are actively placed or excluded in the regulatory regions for the initiation and termination of transcription and translation, indicating their deep involvement or influence in these processes.
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Affiliation(s)
- Osamu Miura
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Toshihiro Ogake
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Takashi Ohyama
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.
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16
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Chen ZX, Oliver B, Zhang YE, Gao G, Long M. Expressed Structurally Stable Inverted Duplicates in Mammalian Genomes as Functional Noncoding Elements. Genome Biol Evol 2017; 9:981-992. [PMID: 28338961 PMCID: PMC5398296 DOI: 10.1093/gbe/evx054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2017] [Indexed: 12/24/2022] Open
Abstract
Inverted duplicates are a type of repetitive DNA motifs consist of two copies of reverse complementary sequences separated by a spacer sequence. They can lead to genome instability and many may have no function, but some functional small RNAs are processed from hairpins transcribed from these elements. It is not clear whether the pervasive numbers of such elements in genomes, especially those of mammals, is the result of high generation rates of neutral or slightly deleterious duplication events or positive selection for functionality. To test the functionality of intergenic inverted duplicates without known functions, we used mirror duplicates, a type of repetitive DNA motifs with few reported functions and little potential to form hairpins when transcribed, as a nonfunctional control. We identified large numbers of inverted duplicates within intergenic regions of human and mouse genomes, as well as 19 other vertebrate genomes. Structure characterization of these inverted duplicates revealed higher proportion to form stable hairpins compared with converted mirror duplicates, suggesting that inverted duplicates may produce hairpin RNAs. Expression profiling across tissues demonstrated that 7.8% of human and 5.7% of mouse inverted duplicates were expressed even under strict criteria. We found that expressed inverted duplicates were more likely to be structurally stable than both unexpressed inverted duplicates and expressed converted mirror duplicates. By dating inverted duplicates in the vertebrate phylogenetic tree, we observed higher conservation of inverted duplicates than mirror duplicates. These observations support the notion that expressed inverted duplicates may be functional through forming hairpin RNAs.
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Affiliation(s)
- Zhen-Xia Chen
- College of Life Sciences and Technology, Huazhong Agricultural University, Wuhan, P.R. China.,National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.,Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing, P.R. China
| | - Brian Oliver
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Yong E Zhang
- Key Laboratory of Zoological Systematics and Evolution and State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, P.R. China.,University of Chinese Academy of Sciences, Beijing, P.R. China
| | - Ge Gao
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing, P.R. China
| | - Manyuan Long
- Department of Ecology and Evolution, University of Chicago
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17
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Brázda V, Kolomazník J, Lýsek J, Hároníková L, Coufal J, Št'astný J. Palindrome analyser - A new web-based server for predicting and evaluating inverted repeats in nucleotide sequences. Biochem Biophys Res Commun 2016; 478:1739-45. [PMID: 27603574 DOI: 10.1016/j.bbrc.2016.09.015] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 09/02/2016] [Indexed: 10/21/2022]
Abstract
DNA cruciform structures play an important role in the regulation of natural processes including gene replication and expression, as well as nucleosome structure and recombination. They have also been implicated in the evolution and development of diseases such as cancer and neurodegenerative disorders. Cruciform structures are formed by inverted repeats, and their stability is enhanced by DNA supercoiling and protein binding. They have received broad attention because of their important roles in biology. Computational approaches to study inverted repeats have allowed detailed analysis of genomes. However, currently there are no easily accessible and user-friendly tools that can analyse inverted repeats, especially among long nucleotide sequences. We have developed a web-based server, Palindrome analyser, which is a user-friendly application for analysing inverted repeats in various DNA (or RNA) sequences including genome sequences and oligonucleotides. It allows users to search and retrieve desired gene/nucleotide sequence entries from the NCBI databases, and provides data on length, sequence, locations and energy required for cruciform formation. Palindrome analyser also features an interactive graphical data representation of the distribution of the inverted repeats, with options for sorting according to the length of inverted repeat, length of loop, and number of mismatches. Palindrome analyser can be accessed at http://bioinformatics.ibp.cz.
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Affiliation(s)
- Václav Brázda
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic.
| | - Jan Kolomazník
- Mendel University in Brno, Zemědělská 1, 613 00, Brno, Czech Republic
| | - Jiří Lýsek
- Mendel University in Brno, Zemědělská 1, 613 00, Brno, Czech Republic
| | - Lucia Hároníková
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic
| | - Jan Coufal
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic
| | - Jiří Št'astný
- Mendel University in Brno, Zemědělská 1, 613 00, Brno, Czech Republic
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18
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Kralovicova J, Patel A, Searle M, Vorechovsky I. The role of short RNA loops in recognition of a single-hairpin exon derived from a mammalian-wide interspersed repeat. RNA Biol 2015; 12:54-69. [PMID: 25826413 PMCID: PMC4615370 DOI: 10.1080/15476286.2015.1017207] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Splice-site selection is controlled by secondary structure through sequestration or approximation of splicing signals in primary transcripts but the exact role of even the simplest and most prevalent structural motifs in exon recognition remains poorly understood. Here we took advantage of a single-hairpin exon that was activated in a mammalian-wide interspersed repeat (MIR) by a mutation stabilizing a terminal triloop, with splice sites positioned close to each other in a lower stem of the hairpin. We first show that the MIR exon inclusion in mRNA correlated inversely with hairpin stabilities. Employing a systematic manipulation of unpaired regions without altering splice-site configuration, we demonstrate a high correlation between exon inclusion of terminal tri- and tetraloop mutants and matching tri-/tetramers in splicing silencers/enhancers. Loop-specific exon inclusion levels and enhancer/silencer associations were preserved across primate cell lines, in 4 hybrid transcripts and also in the context of a distinct stem, but only if its loop-closing base pairs were shared with the MIR hairpin. Unlike terminal loops, splicing activities of internal loop mutants were predicted by their intramolecular Watson-Crick interactions with the antiparallel strand of the MIR hairpin rather than by frequencies of corresponding trinucleotides in splicing silencers/enhancers. We also show that splicing outcome of oligonucleotides targeting the MIR exon depend on the identity of the triloop adjacent to their antisense target. Finally, we identify proteins regulating MIR exon recognition and reveal a distinct requirement of adjacent exons for C-terminal extensions of Tra2α and Tra2β RNA recognition motifs.
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Affiliation(s)
- Jana Kralovicova
- a University of Southampton; Faculty of Medicine ; Southampton , UK
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19
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Ye C, Ji G, Li L, Liang C. detectIR: a novel program for detecting perfect and imperfect inverted repeats using complex numbers and vector calculation. PLoS One 2014; 9:e113349. [PMID: 25409465 PMCID: PMC4237412 DOI: 10.1371/journal.pone.0113349] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 10/22/2014] [Indexed: 11/19/2022] Open
Abstract
Inverted repeats are present in abundance in both prokaryotic and eukaryotic genomes and can form DNA secondary structures--hairpins and cruciforms that are involved in many important biological processes. Bioinformatics tools for efficient and accurate detection of inverted repeats are desirable, because existing tools are often less accurate and time consuming, sometimes incapable of dealing with genome-scale input data. Here, we present a MATLAB-based program called detectIR for the perfect and imperfect inverted repeat detection that utilizes complex numbers and vector calculation and allows genome-scale data inputs. A novel algorithm is adopted in detectIR to convert the conventional sequence string comparison in inverted repeat detection into vector calculation of complex numbers, allowing non-complementary pairs (mismatches) in the pairing stem and a non-palindromic spacer (loop or gaps) in the middle of inverted repeats. Compared with existing popular tools, our program performs with significantly higher accuracy and efficiency. Using genome sequence data from HIV-1, Arabidopsis thaliana, Homo sapiens and Zea mays for comparison, detectIR can find lots of inverted repeats missed by existing tools whose outputs often contain many invalid cases. detectIR is open source and its source code is freely available at: https://sourceforge.net/projects/detectir.
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Affiliation(s)
- Congting Ye
- Department of Automation, Xiamen University, Xiamen, Fujian 361005, China; Department of Biology, Miami University, Oxford, Ohio 45056, United States of America
| | - Guoli Ji
- Department of Automation, Xiamen University, Xiamen, Fujian 361005, China; Innovation Center for Cell Biology, Xiamen University, Xiamen, Fujian 361005, China
| | - Lei Li
- Department of Automation, Xiamen University, Xiamen, Fujian 361005, China; Department of Biology, Miami University, Oxford, Ohio 45056, United States of America
| | - Chun Liang
- Department of Biology, Miami University, Oxford, Ohio 45056, United States of America; State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
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20
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Du X, Gertz EM, Wojtowicz D, Zhabinskaya D, Levens D, Benham CJ, Schäffer AA, Przytycka TM. Potential non-B DNA regions in the human genome are associated with higher rates of nucleotide mutation and expression variation. Nucleic Acids Res 2014; 42:12367-79. [PMID: 25336616 PMCID: PMC4227770 DOI: 10.1093/nar/gku921] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
While individual non-B DNA structures have been shown to impact gene expression, their broad regulatory role remains elusive. We utilized genomic variants and expression quantitative trait loci (eQTL) data to analyze genome-wide variation propensities of potential non-B DNA regions and their relation to gene expression. Independent of genomic location, these regions were enriched in nucleotide variants. Our results are consistent with previously observed mutagenic properties of these regions and counter a previous study concluding that G-quadruplex regions have a reduced frequency of variants. While such mutagenicity might undermine functionality of these elements, we identified in potential non-B DNA regions a signature of negative selection. Yet, we found a depletion of eQTL-associated variants in potential non-B DNA regions, opposite to what might be expected from their proposed regulatory role. However, we also observed that genes downstream of potential non-B DNA regions showed higher expression variation between individuals. This coupling between mutagenicity and tolerance for expression variability of downstream genes may be a result of evolutionary adaptation, which allows reconciling mutagenicity of non-B DNA structures with their location in functionally important regions and their potential regulatory role.
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Affiliation(s)
- Xiangjun Du
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - E Michael Gertz
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Damian Wojtowicz
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Dina Zhabinskaya
- Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - David Levens
- UC Davis Genome Center, University of California Davis, Davis, CA 95616, USA
| | - Craig J Benham
- Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alejandro A Schäffer
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Teresa M Przytycka
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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21
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Zhabinskaya D, Benham CJ. Competitive superhelical transitions involving cruciform extrusion. Nucleic Acids Res 2013; 41:9610-21. [PMID: 23969416 PMCID: PMC3834812 DOI: 10.1093/nar/gkt733] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A DNA molecule under negative superhelical stress becomes susceptible to transitions to alternate structures. The accessible alternate conformations depend on base sequence and compete for occupancy. We have developed a method to calculate equilibrium distributions among the states available to such systems, as well as their average thermodynamic properties. Here we extend this approach to include superhelical cruciform extrusion at both perfect and imperfect inverted repeat (IR) sequences. We find that short IRs do not extrude cruciforms, even in the absence of competition. But as the length of an IR increases, its extrusion can come to dominate both strand separation and B-Z transitions. Although many IRs are present in human genomic DNA, we find that extrusion-susceptible ones occur infrequently. Moreover, their avoidance of transcription start sites in eukaryotes suggests that cruciform formation is rarely involved in mechanisms of gene regulation. We examine a set of clinically important chromosomal translocation breakpoints that occur at long IRs, whose rearrangement has been proposed to be driven by cruciform extrusion. Our results show that the susceptibilities of these IRs to cruciform formation correspond closely with their observed translocation frequencies.
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Affiliation(s)
- Dina Zhabinskaya
- UC Davis Genome Center, University of California, One Shields Avenue, Davis, CA 95616, USA
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22
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Du X, Wojtowicz D, Bowers AA, Levens D, Benham CJ, Przytycka TM. The genome-wide distribution of non-B DNA motifs is shaped by operon structure and suggests the transcriptional importance of non-B DNA structures in Escherichia coli. Nucleic Acids Res 2013; 41:5965-77. [PMID: 23620297 PMCID: PMC3695496 DOI: 10.1093/nar/gkt308] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Although the right-handed double helical B-form DNA is most common under physiological conditions, DNA is dynamic and can adopt a number of alternative structures, such as the four-stranded G-quadruplex, left-handed Z-DNA, cruciform and others. Active transcription necessitates strand separation and can induce such non-canonical forms at susceptible genomic sequences. Therefore, it has been speculated that these non-B DNA motifs can play regulatory roles in gene transcription. Such conjecture has been supported in higher eukaryotes by direct studies of several individual genes, as well as a number of large-scale analyses. However, the role of non-B DNA structures in many lower organisms, in particular proteobacteria, remains poorly understood and incompletely documented. In this study, we performed the first comprehensive study of the occurrence of B DNA-non-B DNA transition-susceptible sites (non-B DNA motifs) within the context of the operon structure of the Escherichia coli genome. We compared the distributions of non-B DNA motifs in the regulatory regions of operons with those from internal regions. We found an enrichment of some non-B DNA motifs in regulatory regions, and we show that this enrichment cannot be simply explained by base composition bias in these regions. We also showed that the distribution of several non-B DNA motifs within intergenic regions separating divergently oriented operons differs from the distribution found between convergent ones. In particular, we found a strong enrichment of cruciforms in the termination region of operons; this enrichment was observed for operons with Rho-dependent, as well as Rho-independent terminators. Finally, a preference for some non-B DNA motifs was observed near transcription factor-binding sites. Overall, the conspicuous enrichment of transition-susceptible sites in these specific regulatory regions suggests that non-B DNA structures may have roles in the transcriptional regulation of specific operons within the E. coli genome.
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Affiliation(s)
- Xiangjun Du
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health 8600 Rockville Pike, Bethesda, MD 20894, USA
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23
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Humphrey-Dixon EL, Sharp R, Schuckers M, Lock R. Comparative genome analysis suggests characteristics of yeast inverted repeats that are important for transcriptional activity. Genome 2011; 54:934-42. [PMID: 22029652 DOI: 10.1139/g11-058] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Inverted repeats are sequences of DNA that, when read in the 5' to 3' direction, have the same sequence on both strands (palindromic portion), with the exception of a small number of nucleotides in the exact center (nonpalindromic spacer). They have been implicated in various DNA-mediated processes including replication, transcription, and genomic instability. At least some of these sequences are capable of forming an alternative DNA structure, called a cruciform, that may be important for mediating these functions. We generated a list of inverted repeats in the Saccharomyces cerevisiae genome and determined which of them are conserved in three related yeasts. We have identified characterisitics of inverted repeats that make them more likely to be conserved than the surrounding DNA and characteristics, such as position and base composition, that make the genes they are associated with likely to be more actively transcribed. This is an important step in determining the functions of this group of genomic elements.
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24
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Chen ZX, Zhang YE, Vibranovski M, Luo J, Gao G, Long M. Deficiency of X-linked inverted duplicates with male-biased expression and the underlying evolutionary mechanisms in the Drosophila genome. Mol Biol Evol 2011; 28:2823-32. [PMID: 21546357 PMCID: PMC3176832 DOI: 10.1093/molbev/msr101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Inverted duplicates (IDs) are pervasive in genomes and have been reported to play functional roles in various biological processes. However, the general underlying evolutionary forces that maintain IDs in genomes remain largely elusive. Through a systematic screening of the Drosophila melanogaster genome, 20,223 IDs were detected in nonrepetitive intergenic regions, far more than expectation under the neutrality model. 3,846 of these IDs were identified to have stable hairpin structure (i.e., the structural IDs). Based on whole-genome transcriptome profiling data, we found 628 unannotated expressed structural IDs, which had significantly different genomic distributions and structural properties from the unexpressed IDs. Among the expressed structural IDs, 130 exhibited higher expression in males than in females (i.e., male-biased expression). Compared with sex-unbiased ones, these male-biased IDs were significantly underrepresented on the X chromosome, similar to previously reported pattern of male-biased protein-coding genes. These analyses suggest that a selection-driven process, rather than a purely neutral mutation-driven mechanism, contributes to the maintenance of IDs in the Drosophila genome.
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Affiliation(s)
- Zhen-Xia Chen
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing, PR China
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25
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Ramreddy T, Sachidanandam R, Strick TR. Real-time detection of cruciform extrusion by single-molecule DNA nanomanipulation. Nucleic Acids Res 2011; 39:4275-83. [PMID: 21266478 PMCID: PMC3105387 DOI: 10.1093/nar/gkr008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
During cruciform extrusion, a DNA inverted repeat unwinds and forms a four-way junction in which two of the branches consist of hairpin structures obtained by self-pairing of the inverted repeats. Here, we use single-molecule DNA nanomanipulation to monitor in real-time cruciform extrusion and rewinding. This allows us to determine the size of the cruciform to nearly base pair accuracy and its kinetics with second-scale time resolution. We present data obtained with two different inverted repeats, one perfect and one imperfect, and extend single-molecule force spectroscopy to measure the torque dependence of cruciform extrusion and rewinding kinetics. Using mutational analysis and a simple two-state model, we find that in the transition state intermediate only the B-DNA located between the inverted repeats (and corresponding to the unpaired apical loop) is unwound, implying that initial stabilization of the four-way (or Holliday) junction is rate-limiting. We thus find that cruciform extrusion is kinetically regulated by features of the hairpin loop, while rewinding is kinetically regulated by features of the stem. These results provide mechanistic insight into cruciform extrusion and help understand the structural features that determine the relative stability of the cruciform and B-form states.
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Affiliation(s)
- T Ramreddy
- Institut Jacques Monod, CNRS UMR 7592, University of Paris - Diderot, 15 rue Hélène Brion, 75205 Paris Cedex 13, France
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