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Greco F, Marzano M, Falanga AP, Terracciano M, Piccialli G, Roviello GN, D'Errico S, Borbone N, Oliviero G. Cytosine-rich oligonucleotides incorporating a non-nucleotide loop: A further step towards the obtainment of physiologically stable i-motif DNA. Int J Biol Macromol 2022; 219:626-636. [PMID: 35952813 DOI: 10.1016/j.ijbiomac.2022.08.016] [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: 06/08/2022] [Revised: 07/12/2022] [Accepted: 08/02/2022] [Indexed: 11/05/2022]
Abstract
i-Motifs, also known as i-tetraplexes, are secondary structures of DNA occurring in cytosine-rich oligonucleotides (CROs) that recall increasing interest in the scientific community for their relevance in various biological processes and DNA nanotechnology. This study reports the design of new structurally modified CROs, named Double-Ended-Linker-CROs (DEL-CROs), capable of forming stable i-motif structures. Here, two C-rich strands having sequences d(AC4A) and d(C6) have been attached, in a parallel fashion, to the two linker's edges by their 3' or 5' ends. The resulting DEL-CROs have been investigated for their capability to form i-motif structures by circular dichroism, poly-acrylamide gel electrophoresis, HPLC-size-exclusion chromatography, and NMR studies. This investigation established that DEL-CROs could form more stable i-motif structures than the corresponding unmodified CROs. In particular, the i-motif formed by DEL-5'-d(C6)2 resulted stable enough to be detected even at near physiological conditions (37 °C, pH 7.0). The results open the way to developing pH-switchable nanocarriers and aptamers based on suitably functionalized DEL-CROs.
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Affiliation(s)
- Francesca Greco
- Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy
| | - Maria Marzano
- Istituto di Scienze Applicate e Sistemi Intelligenti - Unità di Napoli, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Andrea Patrizia Falanga
- Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy
| | - Monica Terracciano
- Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy; Istituto di Scienze Applicate e Sistemi Intelligenti - Unità di Napoli, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Gennaro Piccialli
- Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy; ISBE Italy, Università degli Studi di Napoli Federico II, 80138 Napoli, Italy
| | - Giovanni Nicola Roviello
- Istituto di Biostrutture e Bioimmagini, Consiglio Nazionale delle Ricerche, Via Mezzocannone 16, 80134 Napoli, Italy
| | - Stefano D'Errico
- Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy
| | - Nicola Borbone
- Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy; Istituto di Scienze Applicate e Sistemi Intelligenti - Unità di Napoli, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; ISBE Italy, Università degli Studi di Napoli Federico II, 80138 Napoli, Italy.
| | - Giorgia Oliviero
- ISBE Italy, Università degli Studi di Napoli Federico II, 80138 Napoli, Italy; Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Via Sergio Pansini 5, 80131 Napoli, Italy
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Lepper CP, Williams MAK, Edwards PJB, Filichev VV, Jameson GB. Effects of Pressure and pH on the Physical Stability of an I‐Motif DNA Structure. Chemphyschem 2019; 20:1567-1571. [DOI: 10.1002/cphc.201900145] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 05/01/2019] [Indexed: 12/21/2022]
Affiliation(s)
| | - Martin A. K. Williams
- School of Fundamental Sciences The MacDiarmid Institute and the Riddet InstituteMassey University Palmerston North New Zealand
| | | | | | - Geoffrey B. Jameson
- School of Fundamental Sciences The MacDiarmid Institute and the Riddet InstituteMassey University Palmerston North New Zealand
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3
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DNA-templated gold nanocluster as a novel fluorometric sensor for glutathione determination. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2018.10.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Del Bonis-O'Donnell JT, Pennathur S, Fygenson DK. Changes in Spectra and Conformation of Hairpin DNA-Stabilized Silver Nanoclusters Induced by Stem Sequence Perturbations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:569-76. [PMID: 26685711 DOI: 10.1021/acs.langmuir.5b03934] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
It is well-known that even small perturbations of the DNA sequence can drastically and unpredictably disrupt or alter the fluorescence of DNA-stabilized silver nanoclusters (DNA-AgNCs). Understanding how the structure of DNA affects the nanocluster that it stabilizes is the key to rationalizing such effects. We approach this challenge by strategically modifying the stem sequence of a hairpin DNA that hosts a spectrally pure, red-emitting nanocluster. Most of our modifications (base composition, sequence orientation, and loop location) reduce AgNC fluorescence in purity and shift it in wavelength, but one modification (appending poly(thymidine) to the 3' end of the stem) is inert with respect to fluorescence. Microfluidic capillary electrophoresis reveals that all of the modifications induce conformational changes of the DNA and that the original, spectrally pure nanocluster exists in two structurally distinct conformations. Interestingly, appending five or more thymidines, despite having no effect on fluorescence, eliminates this structural degeneracy. To explain this result, we propose that the original spectrally pure cluster is stabilized by a pair of hairpins whose stems can arrange in either a cis or trans orientation. Finally, we quantify the extent to which thymidine appendages of different lengths can be used to fine-tune the electrophoretic mobility of DNA-AgNC.
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Affiliation(s)
- Jackson Travis Del Bonis-O'Donnell
- Department of Mechanical Engineering, ‡Department of Physics, and §Program in Biomolecular Science & Engineering, University of California , Santa Barbara 93106, United States
| | - Sumita Pennathur
- Department of Mechanical Engineering, ‡Department of Physics, and §Program in Biomolecular Science & Engineering, University of California , Santa Barbara 93106, United States
| | - Deborah K Fygenson
- Department of Mechanical Engineering, ‡Department of Physics, and §Program in Biomolecular Science & Engineering, University of California , Santa Barbara 93106, United States
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5
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Abstract
CONSPECTUS: Most biological processes happen at the nanometer scale, and understanding the energy transformations and material transportation mechanisms within living organisms has proved challenging. To better understand the secrets of life, researchers have investigated artificial molecular motors and devices over the past decade because such systems can mimic certain biological processes. DNA nanotechnology based on i-motif structures is one system that has played an important role in these investigations. In this Account, we summarize recent advances in functional DNA nanotechnology based on i-motif structures. The i-motif is a DNA quadruplex that occurs as four stretches of cytosine repeat sequences form C·CH(+) base pairs, and their stabilization requires slightly acidic conditions. This unique property has produced the first DNA molecular motor driven by pH changes. The motor is reliable, and studies show that it is capable of millisecond running speeds, comparable to the speed of natural protein motors. With careful design, the output of these types of motors was combined to drive micrometer-sized cantilevers bend. Using established DNA nanostructure assembly and functionalization methods, researchers can easily integrate the motor within other DNA assembled structures and functional units, producing DNA molecular devices with new functions such as suprahydrophobic/suprahydrophilic smart surfaces that switch, intelligent nanopores triggered by pH changes, molecular logic gates, and DNA nanosprings. Recently, researchers have produced motors driven by light and electricity, which have allowed DNA motors to be integrated within silicon-based nanodevices. Moreover, some devices based on i-motif structures have proven useful for investigating processes within living cells. The pH-responsiveness of the i-motif structure also provides a way to control the stepwise assembly of DNA nanostructures. In addition, because of the stability of the i-motif, this structure can serve as the stem of one-dimensional nanowires, and a four-strand stem can provide a new basis for three-dimensional DNA structures such as pillars. By sacrificing some accuracy in assembly, we used these properties to prepare the first fast-responding pure DNA supramolecular hydrogel. This hydrogel does not swell and cannot encapsulate small molecules. These unique properties could lead to new developments in smart materials based on DNA assembly and support important applications in fields such as tissue engineering. We expect that DNA nanotechnology will continue to develop rapidly. At a fundamental level, further studies should lead to greater understanding of the energy transformation and material transportation mechanisms at the nanometer scale. In terms of applications, we expect that many of these elegant molecular devices will soon be used in vivo. These further studies could demonstrate the power of DNA nanotechnology in biology, material science, chemistry, and physics.
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Affiliation(s)
- Yuanchen Dong
- Key Laboratory of Organic Optoelectronics & Molecular Engineering of the Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Zhongqiang Yang
- Key Laboratory of Organic Optoelectronics & Molecular Engineering of the Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Dongsheng Liu
- Key Laboratory of Organic Optoelectronics & Molecular Engineering of the Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China
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Arora A, Nair DR, Maiti S. Effect of flanking bases on quadruplex stability and Watson-Crick duplex competition. FEBS J 2009; 276:3628-40. [PMID: 19490117 DOI: 10.1111/j.1742-4658.2009.07082.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Guanine-rich DNA sequences have the ability to fold into four-stranded structures called G-quadruplexes, and are considered as promising anticancer targets. Although the G-quadruplex structure is composed of quartets and interspersed loops, in the genome it is also flanked on each side by numerous bases. The effect of loop length and composition on quadruplex conformation and stability has been well investigated in the past, but the effect of flanking bases on quadruplex stability and Watson-Crick duplex competition has not been addressed. We have studied in detail the effect of flanking bases on quadruplex stability and on duplex formation by the G-quadruplex in the presence of complementary strands using the quadruplex-forming sequence located in the promoter region of the c-kit oncogene. The results obtained from CD, thermal difference spectrum and UV melting demonstrated the effect of flanking bases on quadruplex structure and stability. With the increase in flank length, the increase in the more favorable DeltaH(vH) is accompanied by a striking increase in the unfavorable DeltaS(vH), which resulted in a decrease in the overall DeltaG(vH) of quadruplex formation. Furthermore, CD, fluorescence and isothermal titration calorimetry studies demonstrated that the propensity to attain quadruplex structure decreases with increasing flank length.
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Affiliation(s)
- Amit Arora
- Proteomics and Structural Biology Unit, Institute of Genomics and Integrative Biology, Council for Scientific and Industrial Research, Delhi, India
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Yoshida C, Kuniwake A, Naimuddin M, Nishigaki K. Molecular design guided by a local map of sequence space: DNA aptamers that inhibit cathepsin E. Oligonucleotides 2008; 18:1-8. [PMID: 18321158 DOI: 10.1089/oli.2007.0102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
It has been strongly demanded by a number of people to elevate activities of molecules of a particular function. Currently, there is no general guide available for this purpose. Here we present a novel approach for this; a local sequence space map-directed method for exploring molecules of a higher activity. This approach exploits the knowledge of a local sequence space so far established and obtains the shape of sequence space (map) by intra- and extrapolating the known landscape, which was drawn through the principal coordinates analysis. In this method, we successfully obtained 16 DNA aptamers of cathepsin E (CE) inhibitory activity that have comparable or higher activities than the ancestral ones on which the designed molecules were based. Some of them had a 30% higher activity than the previously reported top one (SFR-6-3). This high efficiency in obtaining functional molecules (16 out of 21 newly designed ones) is by no means usual because most of molecules generated at random are known to have no function, showing the effectiveness of the map-based approach. The selected molecules were confirmed to have the i-motif structure, consistent to the fact that they have a C-rich sequence and their CE-inhibitory activities were measured at an acidic pH, both of which are favorable for the i-motif. This structure of CE-inhibitory aptamers was inferred to contribute to the structural stability but not to the function itself directly.
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Affiliation(s)
- Chuya Yoshida
- Department of Functional Materials Science, Graduate School of Science and Engineering, Saitama University, Saitama Japan
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Han GW, Kopka ML, Langs D, Sawaya MR, Dickerson RE. Crystal structure of an RNA.DNA hybrid reveals intermolecular intercalation: dimer formation by base-pair swapping. Proc Natl Acad Sci U S A 2003; 100:9214-9. [PMID: 12872000 PMCID: PMC170898 DOI: 10.1073/pnas.1533326100] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An intermolecular intercalation of base pairs was found at the CA step in the I222 crystal structure of the RNA.DNA hybrid, r(CAAAGAAAAG).d(CTTTTCTTTG), which contains two-thirds of the polypurine tract sequence of HIV-1 with a substitution of cytosine for the initial adenine. This sequence crystallized in both P212121 and I222 space groups, with an rms difference of only 0.63 A between residues 3 to 18 of the two forms. P212121 and I222 helices are both A-like, but intercalation occurs only in the I222 crystal form. The present structure shows bases stacked in parallel rather than perpendicular as in intercalated DNA (I-DNA). The base intercalation is also different from zipper-like meshing of bases seen in the center of the crystal structure of d(GCGAAAGCT), which does not have Watson-Crick base pairing. The base-step intercalation seen here is reminiscent of domain swapping in proteins; therefore, we call this phenomenon "base-pair swapping." It involves a highly mobile CA step and seems to be sequence-specific and electrostatically stable without disrupting Watson-Crick interactions. It also exhibits a large rise concurrent with unwinding of the helix (low twist). We present a base-pair swapping dimer in nucleic acids.
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Affiliation(s)
- Gye Won Han
- Molecular Biology Institute, University of California, Los Angeles, CA 90095-1570, USA
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9
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Raukas E, Kooli K. Protonation of deoxycytidine residues in dC4 tetraloops: UV spectrophotometric study of dC10 and d(A14C4T14). Biophys Chem 2003; 104:429-47. [PMID: 12878311 DOI: 10.1016/s0301-4622(03)00032-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
It is shown that component analysis could be applied to study the UV difference spectra of cytidine oligomers and hairpin oligonucleotides with cytidines in the loop region in order to account for the melting and titration results in terms of cytidine stacking and protonation. Upon acid titration, the dC(10) oligomer undergoes cooperative conformational transition at pH 6.3 accompanied by protonation and formation of the i-structure with half of the residues protonated. The stability of the hemiprotonated structure increases with decreasing pH, the i-structure persisting still in the region of pH<pK of cytidine. An UV difference spectrum that reflects the stacking/unstacking of hemiprotonated cytidine residues was acquired from the melting and titration experiments of the dC(10) oligomer and used to describe the behavior of the dC(4) loop of the hairpin oligonucleotide d(A(14)C(4)T(14)). It is shown that upon titration, the 50% level of protonation of the deoxycytidine tetraloop is attained at pH 5.0. Simultaneously, the stacking interactions of cytidine residues reach the maximum at this pH with two residues stacked, and thereafter decline again. Only marginal stabilization of the oligomer hairpin (DeltaT(m)=1.5 degrees C) is found to accompany the formation of this single hemiprotonated dC.dC(+) base pair. We propose that at pH 5 the cytidines of the dC(4) loop form a hemiprotonated dC.dC(+) pair stacked with the last dA.dT base pair of the hairpin stem.
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Affiliation(s)
- E Raukas
- Institute of Experimental Biology, Estonian Agricultural University, 76902, Harku, Estonia.
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10
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Park HJ. Evidence for a common molecular basis for sequence recognition of N3-guanine and N3-adenine DNA adducts involving the covalent bonding reaction of (+)-CC-1065. Arch Pharm Res 2002; 25:11-24. [PMID: 11885687 DOI: 10.1007/bf02975255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The antitumor antibiotic (+)-CC-1065 can alkylate N3 of guanine in certain sequences. A previous high-field 1H NMR study on the (+)-CC-1065d[GCGCAATTG*CGC]2 adduct (* indicates the drug alkylation site) showed that drug modification on N3 of guanine results in protonation of the cross-strand cytosine [Park, H.-J.; Hurley, L. H. J. Am. Chem. Soc. 1997, 119, 629.]. In this contribution we describe a further analysis of the NMR data sets together with restrained molecular dynamics. This study provides not only a solution structure of the (+)-CC-1065(N3-guanine) DNA duplex adduct but also new insight into the molecular basis for the sequence-specific interaction between (+)-CC-1065 and N3-guanine in the DNA duplex. On the basis of NOESY data, we propose that the narrow minor groove at the 7T8T step and conformational kinks at the junctions of 16C17A and 18A19T are both related to DNA bending in the drugDNA adduct. Analysis of the one-dimensional 1H NMR (in H2O) data and rMD trajectories strongly suggests that hydrogen bonding linkages between the 8-OH group of the (+)-CC-1065 A-subunit and the 9G10C phosphate via a water molecule are present. All the phenomena observed here in the (+)-CC-1065(N3-guanine) adduct at 5'-AATTG* are reminiscent of those obtained from the studies on the (+)-CC-1065(N3-adenine) adduct at 5'-AGTTA*, suggesting that (+)-CC-1065 takes advantage of the conformational flexibility of the 5'-TPu step to entrap the bent structure required for the covalent bonding reaction. This study reveals a common molecular basis for (+)-CC-1065 alkylation at both 5'-TTG* and 5'-TTA*, which involves a trapping out of sequence-dependent DNA conformational flexibility as well as sequence-dependent general acid and general base catalysis by duplex DNA.
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Affiliation(s)
- Hyun-Ju Park
- College of Pharmacy, Sungkyunkwan University, Suwon, Korea.
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11
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Pataskar SS, Dash D, Brahmachari SK. Intramolecular i-motif structure at acidic pH for progressive myoclonus epilepsy (EPM1) repeat d(CCCCGCCCCGCG)n. J Biomol Struct Dyn 2001; 19:307-13. [PMID: 11697735 DOI: 10.1080/07391102.2001.10506741] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The most common mutation associated with Progressive Myoclonus Epilepsy (EPM1) of Unverricht-Lundberg type is the expansion of a dodecamer repeat, d(CCCCGCCCCGCG)n. We show that the C-rich strand of this repeat (2-3 copies) forms intercalated i-motif structure at acidic pH as judged by CD spectroscopy and anomalous gel electrophoretic mobility. The stability of the structure increases with the increase in the length of the repeat. Transient formation of stable, folded back structure like i-motif could play an important role in the mechanism of expansion of this repeat.
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Affiliation(s)
- S S Pataskar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore
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12
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Shepard W, Cruse WB, Fourme R, de la Fortelle E, Prangé T. A zipper-like duplex in DNA: the crystal structure of d(GCGAAAGCT) at 2.1 A resolution. Structure 1998; 6:849-61. [PMID: 9687367 DOI: 10.1016/s0969-2126(98)00087-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The replication origin of the single-stranded (ss)DNA bacteriophage G4 has been proposed to fold into a hairpin loop containing the sequence GCGAAAGC. This sequence comprises a purine-rich motif (GAAA), which also occurs in conserved repetitive sequences of centromeric DNA. ssDNA analogues of these sequences often show exceptional stability which is associated with hairpin loops or unusual duplexes, and may be important in DNA replication and centromere function. Nuclear magnetic resonance (NMR) studies indicate that the GCGAAAGC sequence forms a hairpin loop in solution, while centromere-like repeats dimerise into unusual duplexes. The factors stabilising these unusual secondary structure elements in ssDNA, however, are poorly understood. RESULTS The nonamer d(GCGAAAGCT) was crystallised as a bromocytosine derivative in the presence of cobalt hexammine. The crystal structure, solved by the multiple wavelength anomalous dispersion (MAD) method at the bromine K-edge, reveals an unexpected zipper-like motif in the middle of a standard B-DNA duplex. Four central adenines, flanked by two sheared G.A mismatches, are intercalated and stacked on top of each other without any interstrand Watson-Crick base pairing. The cobalt hexammine cation appears to participate only in crystal cohesion. CONCLUSIONS The GAAA consensus sequence can dimerise into a stable zipper-like duplex as well as forming a hairpin loop. The arrangement closes the minor groove and exposes the intercalated, unpaired, adenines to the solvent and DNA-binding proteins. Such a motif, which can transform into a hairpin, should be considered as a structural option in modelling DNA and as a potential binding site, where it could have a role in DNA replication, nuclease resistance, ssDNA genome packaging and centromere function.
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Affiliation(s)
- W Shepard
- LURE, Université Paris-Sud, Orsay, France.
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13
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Robidoux S, Damha MJ. D-2-deoxyribose and D-arabinose, but not D-ribose, stabilize the cytosine tetrad (i-DNA) structure. J Biomol Struct Dyn 1997; 15:529-35. [PMID: 9439999 DOI: 10.1080/07391102.1997.10508963] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Described here are studies exploring the effect of the sugar-phosphate backbone on the stability of i-tetrads in solution [K. Gehring et al. Nature 363, 561-565 (1993)]. In the accompanying paper, branched oligonucleotides are shown to be effective probes for organizing oligodeoxycytidine strands into I-motif structures (C-tetrads). Specifically, the joining of a pair of parallel deoxycytidylate strands with a riboadenosine "linker" leads to marked enhancement in stability of the tetrad structure. To further characterize the nature of the sugar-sugar interactions in this novel structure, branched oligonucleotides containing D-arabinocytidine and D-ribocytidine were synthesized and their association properties examined. The ribo oligomers were prepared in two regioisomeric forms differing only in the connectivities of the deoxycytidine strands, i.e., 3'-to-5' versus 2'-to-5' linked dC5 strands. The branched D-deoxycytidine analogue, rA(2',5'-dC5)3',5'-dC5, which previously has been shown to fold into a bimolecular I-motif, served as model system. It is found that the arabinose substitution leads to hypochromic structures that are characteristic of four-stranded intercalated DNA and has little, if any, effect on the stability of the complex formed. Parallel experiments with the branched ribocytidine analogs gave very weak or no discernible UV transitions, consistent with no strand association in this case [Lacroix et al., Biochemistry 35, 8715-8722 (1996)]. These results are discussed in relation to expected steric interactions of oligocytidine strands within the I-structure. The findings increase our understanding of the impact of the sugar and internucleotide connectivity on the stability of this higher-order nucleic acid structure.
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Affiliation(s)
- S Robidoux
- Department of Chemistry, McGill University, Montreal, QC, Canada
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14
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Robidoux S, Klinck R, Gehring K, Damha MJ. Association of branched oligonucleotides into the i-motif. J Biomol Struct Dyn 1997; 15:517-27. [PMID: 9439998 DOI: 10.1080/07391102.1997.10508962] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The unique architecture of branched oligonucleotides mimicking lariat RNA introns [Wallace and Edmons, Proc. Natl. Acad. Sci. USA 80, 950-954 (1983)] was exploited to study compounds that associate as two parallel duplexes with intercalating C/C+ base pairs (i-motif DNA) [Gehring et al. Nature 363, 561-565 (1993)]. The formation of a branched cytosine tetrad was induced by joining the 5'-ends of pair of pentadeoxycytidine strands with a branching riboadenosine (rA) linker. This arrangement causes the orientation of the dC strands to be parallel, and forces the formation of a C/C+ duplex that self-associates into i-DNA. Presence of the i-motif in this structure is supported by thermal denaturation, native gel electrophoresis, CD, and NMR spectroscopy.
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Affiliation(s)
- S Robidoux
- Department of Chemistry, McGill University, Montreal, QC, Canada
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15
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Gallego J, Chou SH, Reid BR. Centromeric pyrimidine strands fold into an intercalated motif by forming a double hairpin with a novel T:G:G:T tetrad: solution structure of the d(TCCCGTTTCCA) dimer. J Mol Biol 1997; 273:840-56. [PMID: 9367776 DOI: 10.1006/jmbi.1997.1361] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The solution structures of the oligodeoxynucleotides d(CCCGTTTCC) and d(TCCCGTTTCCA) have been determined by two-dimensional NMR spectroscopy. These oligomers are part of a DNA box in human centromeric alpha satellite targeted by the centromere protein B (CENP-B). Both CENP-B and its recognition box in alphoid DNA are conserved in mammals, suggesting an important biological role. At acidic pH, d(CCCGTTTCC), d(TCCCGTTTCCA) and the full d(TCCCGTTTCCAACGAAG) CENP-B box strand all fold and dimerize in solution forming a stable bimolecular structure containing two GTTT hairpin loops that interact through a novel T : G : G : T tetrad. The stem region of the dimer is a four-stranded intercalated motif in which the hairpin monomers are parallel and held together by C : C+ hydrogen-bonding and intercalation. The loops are at the same end of the dimer and lie across the narrow grooves of the tetraplex. They are remarkably structured and stabilized by base-base cross-stacking, sugar-base stacking, and parallel G:G and antiparallel G:T pairing. In the d(TCCCGTTTCCA)2 structure, the intercalated motif is continued at the other end of the dimer with unpaired but stacked adenine and thymine bases. The possible biological implications of these structures are discussed.
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Affiliation(s)
- J Gallego
- Chemistry Department, University of Washington Seattle, WA 98195, USA
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16
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Catasti P, Chen X, Deaven LL, Moyzis RK, Bradbury EM, Gupta G. Cystosine-rich strands of the insulin minisatellite adopt hairpins with intercalated cytosine+.cytosine pairs. J Mol Biol 1997; 272:369-82. [PMID: 9325097 DOI: 10.1006/jmbi.1997.1248] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previously, we reported the high resolution NMR structure of the hairpin G-quartet structure formed by the G-rich strand of the insulin minisatellite of repeat sequence, (ACAG4TGTG4/TGTC4ACAC4) located upstream of the human insulin gene. Here, we report structural studies on the C-rich strand of this insulin minisatellite. First, we show by high resolution NMR that (C4TGTC4) forms a hairpin dimer with intercalated C+.C pairs (referred to as the hairpin i-motif); 340 NOE distance constraints uniquely define the nature of hairpin folding and the pattern of C+.C intercalation. Second, we show by one-dimensional NMR spectroscopy and molecular modeling studies that (C4TGTC4ACA4TGTC4) forms an intramolecularly folded hairpin with intercalated C+.C pairs. Third, we demonstrate by in vitro replication studies that several such hairpin i-motifs are present in long (C4TGTC4ACA)n (n>/=6) sequences, even in the presence of their complementary strands. Finally, we discuss structural and biological significance of the hairpin i-motifs formed by the C-rich strands of the insulin minisatellite.
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Affiliation(s)
- P Catasti
- Theoretical Biology and Biophysics, T-10, MS-K710, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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Nonin S, Phan AT, Leroy JL. Solution structure and base pair opening kinetics of the i-motif dimer of d(5mCCTTTACC): a noncanonical structure with possible roles in chromosome stability. Structure 1997; 5:1231-46. [PMID: 9331414 DOI: 10.1016/s0969-2126(97)00273-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Repetitive cytosine-rich DNA sequences have been identified in telomeres and centromeres of eukaryotic chromosomes. These sequences play a role in maintaining chromosome stability during replication and may be involved in chromosome pairing during meiosis. The C-rich repeats can fold into an 'i-motif' structure, in which two parallel-stranded duplexes with hemiprotonated C.C+ pairs are intercalated. Previous NMR studies of naturally occurring repeats have produced poor NMR spectra. This led us to investigate oligonucleotides, based on natural sequences, to produce higher quality spectra and thus provide further information as to the structure and possible biological function of the i-motif. RESULTS NMR spectroscopy has shown that d(5mCCTTTACC) forms an i-motif dimer of symmetry-related and intercalated folded strands. The high-definition structure is computed on the basis of the build-up rates of 29 intraresidue and 35 interresidue nuclear Overhauser effect (NOE) connectivities. The i-motif core includes intercalated interstrand C.C+ pairs stacked in the order 2*.8/1.7*/1*.7/2.8* (where one strand is distinguished by an asterisk and the numbers relate to the base positions within the repeat). The TTTA sequences form two loops which span the two wide grooves on opposite sides of the i-motif core; the i-motif core is extended at both ends by the stacking of A6 onto C2.C8+. The lifetimes of pairs C2.C8+ and 5mC1.C7+ are 1 ms and 1 s, respectively, at 15 degrees C. Anomalous exchange properties of the T3 imino proton indicate hydrogen bonding to A6 N7 via a water bridge. The d(5mCCTTTTCC) deoxyoligonucleotide, in which position 6 is occupied by a thymidine instead of an adenine, also forms a symmetric i-motif dimer. However, in this structure the two TTTT loops are located on the same side of the i-motif core and the C.C+ pairs are formed by equivalent cytidines stacked in the order 8*.8/1.1*/7*.7/2.2*. CONCLUSIONS Oligodeoxynucleotides containing two C-rich repeats can fold and dimerize into an i-motif. The change of folding topology resulting from the substitution of a single nucleoside emphasizes the influence of the loop residues on the i-motif structure formed by two folded strands.
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Affiliation(s)
- S Nonin
- Groupe de Biophysique, de l'Ecole Polytechnique et de l'URA, CNRS, Palaiseau, France
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