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Sarkar S, Colón-Roura G, Pearse A, Armitage BA. Targeting a KRAS i-motif forming sequence by unmodified and gamma-modified peptide nucleic acid oligomers. Biopolymers 2023; 114:e23529. [PMID: 36573547 PMCID: PMC10078108 DOI: 10.1002/bip.23529] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 12/04/2022] [Accepted: 12/07/2022] [Indexed: 12/28/2022]
Abstract
Growing interest in i-motif DNA as a transcriptional regulatory element motivates development of synthetic molecules capable of targeting these structures. In this study, we designed unmodified peptide nucleic acid (PNA) and gamma-modified PNA (γPNA) oligomers complementary to an i-motif forming sequence derived from the promoter of the KRAS oncogene. Biophysical techniques such as circular dichroism (CD) spectroscopy, CD melting, and fluorescence spectroscopy demonstrated the successful invasion of the i-motif by PNA and γPNA. Both PNA and γPNA showed very strong binding to the target sequence with high thermal stability of the resulting heteroduplexes. Interestingly fluorescence and CD experiments indicated formation of an intermolecular i-motif structure via the overhangs of target-probe heteroduplexes formed by PNA/γPNA invasion of the intramolecular i-motif. Targeting promoter i-motif forming sequences with high-affinity oligonucleotide mimics like γPNAs may represent a new approach for inhibiting KRAS transcription, thereby representing a potentially useful anti-cancer strategy.
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Affiliation(s)
- Srijani Sarkar
- Department of Chemistry and Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Gabriela Colón-Roura
- Department of Chemistry and Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Alexander Pearse
- Department of Chemistry and Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Bruce A Armitage
- Department of Chemistry and Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
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Shepard CP, Emehiser RG, Karmakar S, Hrdlicka PJ. Factors Impacting Invader-Mediated Recognition of Double-Stranded DNA. Molecules 2022; 28. [PMID: 36615321 DOI: 10.3390/molecules28010127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 12/16/2022] [Accepted: 12/20/2022] [Indexed: 12/28/2022]
Abstract
The development of chemically modified oligonucleotides enabling robust, sequence-unrestricted recognition of complementary chromosomal DNA regions has been an aspirational goal for scientists for many decades. While several groove-binding or strand-invading probes have been developed towards this end, most enable recognition of DNA only under limited conditions (e.g., homopurine or short mixed-sequence targets, low ionic strength, fully modified probe strands). Invader probes, i.e., DNA duplexes modified with +1 interstrand zippers of intercalator-functionalized nucleotides, are predisposed to recognize DNA targets due to their labile nature and high affinity towards complementary DNA. Here, we set out to gain further insight into the design parameters that impact the thermal denaturation properties and binding affinities of Invader probes. Towards this end, ten Invader probes were designed, and their biophysical properties and binding to model DNA hairpins and chromosomal DNA targets were studied. A Spearman's rank-order correlation analysis of various parameters was then performed. Densely modified Invader probes were found to result in efficient recognition of chromosomal DNA targets with excellent binding specificity in the context of denaturing or non-denaturing fluorescence in situ hybridization (FISH) experiments. The insight gained from the initial phase of this study informed subsequent probe optimization, which yielded constructs displaying improved recognition of chromosomal DNA targets. The findings from this study will facilitate the design of efficient Invader probes for applications in the life sciences.
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Ahuja JS, Harvey CS, Wheeler DL, Lichten M. Repeated strand invasion and extensive branch migration are hallmarks of meiotic recombination. Mol Cell 2021; 81:4258-4270.e4. [PMID: 34453891 PMCID: PMC8541907 DOI: 10.1016/j.molcel.2021.08.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/09/2021] [Accepted: 07/30/2021] [Indexed: 12/19/2022]
Abstract
Currently favored models for meiotic recombination posit that both noncrossover and crossover recombination are initiated by DNA double-strand breaks but form by different mechanisms: noncrossovers by synthesis-dependent strand annealing and crossovers by formation and resolution of double Holliday junctions centered around the break. This dual mechanism hypothesis predicts different hybrid DNA patterns in noncrossover and crossover recombinants. We show that these predictions are not upheld, by mapping with unprecedented resolution parental strand contributions to recombinants at a model locus. Instead, break repair in both noncrossovers and crossovers involves synthesis-dependent strand annealing, often with multiple rounds of strand invasion. Crossover-specific double Holliday junction formation occurs via processes involving branch migration as an integral feature, one that can be separated from repair of the break itself. These findings reveal meiotic recombination to be a highly dynamic process and prompt a new view of the relationship between crossover and noncrossover recombination.
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Affiliation(s)
- Jasvinder S Ahuja
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Catherine S Harvey
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - David L Wheeler
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Michael Lichten
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
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Hinch AG, Becker PW, Li T, Moralli D, Zhang G, Bycroft C, Green C, Keeney S, Shi Q, Davies B, Donnelly P. The Configuration of RPA, RAD51, and DMC1 Binding in Meiosis Reveals the Nature of Critical Recombination Intermediates. Mol Cell 2020; 79:689-701.e10. [PMID: 32610038 PMCID: PMC7447979 DOI: 10.1016/j.molcel.2020.06.015] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 04/07/2020] [Accepted: 06/04/2020] [Indexed: 01/05/2023]
Abstract
Meiotic recombination proceeds via binding of RPA, RAD51, and DMC1 to single-stranded DNA (ssDNA) substrates created after formation of programmed DNA double-strand breaks. Here we report high-resolution in vivo maps of RPA and RAD51 in meiosis, mapping their binding locations and lifespans to individual homologous chromosomes using a genetically engineered hybrid mouse. Together with high-resolution microscopy and DMC1 binding maps, we show that DMC1 and RAD51 have distinct spatial localization on ssDNA: DMC1 binds near the break site, and RAD51 binds away from it. We characterize inter-homolog recombination intermediates bound by RPA in vivo, with properties expected for the critical displacement loop (D-loop) intermediates. These data support the hypothesis that DMC1, not RAD51, performs strand exchange in mammalian meiosis. RPA-bound D-loops can be resolved as crossovers or non-crossovers, but crossover-destined D-loops may have longer lifespans. D-loops resemble crossover gene conversions in size, but their extent is similar in both repair pathways.
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Affiliation(s)
| | - Philipp W Becker
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Tao Li
- Howard Hughes Medical Institute, Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Hefei National Laboratory for Physical Sciences at the Microscale, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Daniela Moralli
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Gang Zhang
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Clare Bycroft
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Catherine Green
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Scott Keeney
- Howard Hughes Medical Institute, Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Qinghua Shi
- Hefei National Laboratory for Physical Sciences at the Microscale, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Benjamin Davies
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Peter Donnelly
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK; Department of Statistics, University of Oxford, Oxford, UK.
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Ong AAL, Tan J, Bhadra M, Dezanet C, Patil KM, Chong MS, Kierzek R, Decout JL, Roca X, Chen G. RNA Secondary Structure-Based Design of Antisense Peptide Nucleic Acids for Modulating Disease-Associated Aberrant Tau Pre-mRNA Alternative Splicing. Molecules 2019; 24:molecules24163020. [PMID: 31434312 PMCID: PMC6720520 DOI: 10.3390/molecules24163020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 08/14/2019] [Accepted: 08/19/2019] [Indexed: 12/18/2022] Open
Abstract
Alternative splicing of tau pre-mRNA is regulated by a 5' splice site (5'ss) hairpin present at the exon 10-intron 10 junction. Single mutations within the hairpin sequence alter hairpin structural stability and/or the binding of splicing factors, resulting in disease-causing aberrant splicing of exon 10. The hairpin structure contains about seven stably formed base pairs and thus may be suitable for targeting through antisense strands. Here, we used antisense peptide nucleic acids (asPNAs) to probe and target the tau pre-mRNA exon 10 5'ss hairpin structure through strand invasion. We characterized by electrophoretic mobility shift assay the binding of the designed asPNAs to model tau splice site hairpins. The relatively short (10-15 mer) asPNAs showed nanomolar binding to wild-type hairpins as well as a disease-causing mutant hairpin C+19G, albeit with reduced binding strength. Thus, the structural stabilizing effect of C+19G mutation could be revealed by asPNA binding. In addition, our cell culture minigene splicing assay data revealed that application of an asPNA targeting the 3' arm of the hairpin resulted in an increased exon 10 inclusion level for the disease-associated mutant C+19G, probably by exposing the 5'ss as well as inhibiting the binding of protein factors to the intronic spicing silencer. On the contrary, the application of asPNAs targeting the 5' arm of the hairpin caused an increased exon 10 exclusion for a disease-associated mutant C+14U, mainly by blocking the 5'ss. PNAs could enter cells through conjugation with amino sugar neamine or by cotransfection with minigene plasmids using a commercially available transfection reagent.
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Affiliation(s)
- Alan Ann Lerk Ong
- NTU Institute for Health Technologies (HeathTech NTU), Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Jiazi Tan
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Malini Bhadra
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Clément Dezanet
- University Grenoble Alpes/CNRS, Département de Pharmacochimie Moléculaire, ICMG FR 2607, UMR 5063, 470 Rue de la Chimie, F-38041 Grenoble, France
| | - Kiran M Patil
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Mei Sian Chong
- Geriatic Education & Research Institute, 2 Yishun Central 2, Singapore 768024, Singapore
| | - Ryszard Kierzek
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Jean-Luc Decout
- University Grenoble Alpes/CNRS, Département de Pharmacochimie Moléculaire, ICMG FR 2607, UMR 5063, 470 Rue de la Chimie, F-38041 Grenoble, France
| | - Xavier Roca
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Gang Chen
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
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Mehta A, Beach A, Haber JE. Homology Requirements and Competition between Gene Conversion and Break-Induced Replication during Double-Strand Break Repair. Mol Cell 2017; 65:515-526.e3. [PMID: 28065599 DOI: 10.1016/j.molcel.2016.12.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/27/2016] [Accepted: 12/01/2016] [Indexed: 11/27/2022]
Abstract
Saccharomyces cerevisiae mating-type switching is initiated by a double-strand break (DSB) at MATa, leaving one cut end perfectly homologous to the HMLα donor, while the second end must be processed to remove a non-homologous tail before completing repair by gene conversion (GC). When homology at the matched end is ≤150 bp, efficient repair depends on the recombination enhancer, which tethers HMLα near the DSB. Thus, homology shorter than an apparent minimum efficient processing segment can be rescued by tethering the donor near the break. When homology at the second end is ≤150 bp, second-end capture becomes inefficient and repair shifts from GC to break-induced replication (BIR). But when pol32 or pif1 mutants block BIR, GC increases 3-fold, indicating that the steps blocked by these mutations are reversible. With short second-end homology, absence of the RecQ helicase Sgs1 promotes gene conversion, whereas deletion of the FANCM-related Mph1 helicase promotes BIR.
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Affiliation(s)
- Anuja Mehta
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Annette Beach
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
| | - James E Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA.
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Abstract
Cancer is recognized as a serious health challenge both in the United States and throughout the world. While early detection and diagnosis of cancer leads to decreased mortality rates, current screening methods require significant time and costly equipment. Recently, increased levels of certain micro-ribonucleic acids (miRNAs) in the blood have been linked to the presence of cancer. While blood-based biomarkers have been used for years in cancer detection, studies analyzing trace amounts of miRNAs in blood and serum samples are just beginning. Recent developments in deoxyribonucleic acid (DNA) nanotechnology and DNA computing have shown that it is possible to construct nucleic-acid-based chemical networks that accept miRNAs as inputs, perform Boolean logic functions on those inputs, and generate as an output a large number of DNA strands that can readily be detected. Since miRNAs occur in blood in low abundance, these networks would allow for amplification without using polymerase chain reaction. In this study, we report initial progress in the development of a DNA-based cross-catalytic network engineered to amplify specific cancer-related miRNAs. Subcomponents of the DNA network were tested individually, and their operation in serum, as well as a mixture of serum with sodium dodecyl sulfate, is demonstrated. Preliminary simulations of the full cross-catalytic network indicate successful operation.
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Affiliation(s)
- Elton Graugnard
- Department of Materials Science & Engineering, Boise State University, Boise, ID 83725 USA
| | - Amber Cox
- Department of Materials Science & Engineering, Boise State University, Boise, ID 83725 USA
| | - Jeunghoon Lee
- Department of Chemistry & Biochemistry, Boise State University, Boise, ID 83725 USA
| | - Cheryl Jorcyk
- Department of Biological Sciences, Boise State University, Boise, ID 83725 USA
| | - Bernard Yurke
- Departments of Materials Science & Engineering and Electrical & Computer Engineering, Boise State University, Boise, ID 83725 USA
| | - William L. Hughes
- Department of Materials Science & Engineering, Boise State University, Boise, ID 83725 USA ()
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