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Nucleic Acids Research Mar 2003The conformational pathways and the free energy variations for base opening into the major and minor grooves of a B-DNA duplex are studied using umbrella sampling...
The conformational pathways and the free energy variations for base opening into the major and minor grooves of a B-DNA duplex are studied using umbrella sampling molecular dynamics simulations. We compare both GC and AT base pair opening within a double-stranded d(GAGAGAGAGAGAG)* d(CTCTCTCTCTCTC) oligomer, and we are also able to study the impact of opening on the conformational and dynamic properties of DNA and on the surrounding solvent. The results indicate a two-stage opening process with an initial coupling of the movements of the bases within the perturbed base pair. Major and minor groove pathways are energetically comparable in the case of the pyrimidine bases, but the major groove pathway is favored for the larger purine bases. Base opening is coupled to changes in specific backbone dihedrals and certain helical distortions, including untwisting and bending, although all these effects are dependent on the particular base involved. Partial opening also leads to well defined water bridging sites, which may play a role in stabilizing the perturbed base pairs.
Topics: Base Pairing; Binding Sites; Computer Simulation; DNA; Hydrogen Bonding; Nucleic Acid Conformation; Thermodynamics; Water
PubMed: 12595551
DOI: 10.1093/nar/gkg239 -
Nature Communications Aug 2023Rational design of self-assembled DNA nanostructures has become one of the fastest-growing research areas in molecular science. Particular attention is focused on the...
Rational design of self-assembled DNA nanostructures has become one of the fastest-growing research areas in molecular science. Particular attention is focused on the development of dynamic DNA nanodevices whose configuration and function are regulated by specific chemical inputs. Herein, we demonstrate the concept of metal-mediated base-pair switching to induce inter- and intramolecular DNA strand displacement in a metal-responsive manner. The 5-hydroxyuracil (U) nucleobase is employed as a metal-responsive unit, forming both a hydrogen-bonded U-A base pair and a metal-mediated U-Gd-U base pair. Metal-mediated strand displacement reactions are demonstrated under isothermal conditions based on the base-pair switching between U-A and U-Gd-U. Furthermore, metal-responsive DNA tweezers and allosteric DNAzymes are developed as typical models for DNA nanodevices simply by incorporating U bases into the sequence. The metal-mediated base-pair switching will become a versatile strategy for constructing stimuli-responsive DNA nanostructures, expanding the scope of dynamic DNA nanotechnology.
Topics: Base Pairing; DNA; DNA, Catalytic; Hydrogen; Metals
PubMed: 37620299
DOI: 10.1038/s41467-023-40353-3 -
Nucleic Acids Research Aug 2022The use of multiple drugs simultaneously targeting DNA is a promising strategy in cancer therapy for potentially overcoming single drug resistance. In support of this...
The use of multiple drugs simultaneously targeting DNA is a promising strategy in cancer therapy for potentially overcoming single drug resistance. In support of this concept, we report that a combination of actinomycin D (ActD) and echinomycin (Echi), can interact in novel ways with native and mismatched DNA sequences, distinct from the structural effects produced by either drug alone. Changes in the former with GpC and CpG steps separated by a A:G or G:A mismatch or in a native DNA with canonical G:C and C:G base pairs, result in significant asymmetric backbone twists through staggered intercalation and base pair modulations. A wobble or Watson-Crick base pair at the two drug-binding interfaces can result in a single-stranded 'chair-shaped' DNA duplex with a straight helical axis. However, a novel sugar-edged hydrogen bonding geometry in the G:A mismatch leads to a 'curved-shaped' duplex. Two non-canonical G:C Hoogsteen base pairings produce a sharply kinked duplex in different forms and a four-way junction-like superstructure, respectively. Therefore, single base pair modulations on the two drug-binding interfaces could significantly affect global DNA structure. These structures thus provide a rationale for atypical DNA recognition via multiple DNA intercalators and a structural basis for the drugs' potential synergetic use.
Topics: Base Pairing; DNA; Hydrogen Bonding; Molecular Structure; Nucleic Acid Conformation
PubMed: 35871296
DOI: 10.1093/nar/gkac629 -
MBio Feb 2023Replication-initiating HUH endonucleases (Reps) are sequence-specific nucleases that cleave and rejoin single-stranded DNA (ssDNA) during rolling-circle replication....
Replication-initiating HUH endonucleases (Reps) are sequence-specific nucleases that cleave and rejoin single-stranded DNA (ssDNA) during rolling-circle replication. These functions are mediated by covalent linkage of the Rep to its substrate post cleavage. Here, we describe the structures of the endonuclease domain from the Muscovy duck circovirus Rep in complex with its cognate ssDNA 10-mer with and without manganese in the active site. Structural and functional analyses demonstrate that divalent cations play both catalytic and structural roles in Reps by polarizing and positioning their substrate. Further structural comparisons highlight the importance of an intramolecular substrate Watson-Crick (WC) base pairing between the -4 and +1 positions. Subsequent kinetic and functional analyses demonstrate a functional dependency on WC base pairing between these positions regardless of the pair's identity (i.e., A·T, T·A, G·C, or C·G), highlighting a structural specificity for substrate interaction. Finally, considering how well WC swaps were tolerated , we sought to determine to what extent the canonical -4T·+1A pairing is conserved in circular Rep-encoding single-stranded DNA viruses and found evidence of noncanonical pairings in a minority of these genomes. Altogether, our data suggest that substrate intramolecular WC base pairing is a universal requirement for separation and reunion of ssDNA in Reps. Circular Rep-encoding single-stranded DNA (CRESS-DNA) viruses are a ubiquitous group of viruses that infect organisms across all domains of life. These viruses negatively impact both agriculture and human health. All members of this viral family employ a multifunctional nuclease (Rep) to initiate replication. Reps are structurally similar throughout this family, making them targets of interest for viral inhibition strategies. Here, we investigate the functional dependencies of the Rep protein from Muscovy duck circovirus for ssDNA interaction. We demonstrate that this Rep requires an intramolecular Watson-Crick base pairing for origin of replication (Ori) recognition and interaction. We show that noncognate base pair swaps are well tolerated, highlighting a local structural specificity over sequence specificity. Bioinformatic analysis found that the vast majority of CRESS-DNA Oris form base pairs in conserved positions, suggesting this pairing is a universal requirement for replication initiation in the CRESS-DNA virus family.
Topics: Humans; Base Pairing; DNA, Single-Stranded; Endonucleases; Circovirus
PubMed: 36541758
DOI: 10.1128/mbio.02587-22 -
Nucleic Acids Research Apr 2019RNA structures possess multiple levels of structural organization. A secondary structure, made of Watson-Crick helices connected by loops, forms a scaffold for the...
RNA structures possess multiple levels of structural organization. A secondary structure, made of Watson-Crick helices connected by loops, forms a scaffold for the tertiary structure. The 3D structures adopted by these loops are therefore critical determinants shaping the global 3D architecture. Earlier studies showed that these local 3D structures can be described as conserved sets of ordered non-Watson-Crick base pairs called RNA structural modules. Unfortunately, the computational efficiency and scope of the current 3D module identification methods are too limited yet to benefit from all the knowledge accumulated in the module databases. We present BayesPairing, an automated, efficient and customizable tool for (i) building Bayesian networks representing RNA 3D modules and (ii) rapid identification of 3D modules in sequences. BayesPairing uses a flexible definition of RNA 3D modules that allows us to consider complex architectures such as multi-branched loops and features multiple algorithmic improvements. We benchmarked our methods using cross-validation techniques on 3409 RNA chains and show that BayesPairing achieves up to ∼70% identification accuracy on module positions and base pair interactions. BayesPairing can handle a broader range of motifs (versatility) and offers considerable running time improvements (efficiency), opening the door to a broad range of large-scale applications.
Topics: Automation; Base Pairing; Bayes Theorem; Databases, Genetic; Datasets as Topic; RNA; Reproducibility of Results; Time Factors
PubMed: 30828711
DOI: 10.1093/nar/gkz102 -
Methods (San Diego, Calif.) Mar 2009Non-canonical base pairs play important roles in organizing the complex three-dimensional folding of RNA. Here, we outline methodology developed both to analyze the... (Review)
Review
Non-canonical base pairs play important roles in organizing the complex three-dimensional folding of RNA. Here, we outline methodology developed both to analyze the spatial patterns of interacting base pairs in known RNA structures and to reconstruct models from the collective experimental information. We focus attention on the structural context and deformability of the seven pairing patterns found in greatest abundance in the helical segments in a set of well-resolved crystal structures, including (i-ii) the canonical A.U and G.C Watson-Crick base pairs, (iii) the G.U wobble pair, (iv) the sheared G.A pair, (v) the A.U Hoogsteen pair, (vi) the U.U wobble pair, and (vii) the G.A Watson-Crick-like pair. The non-canonical pairs stand out from the canonical associations in terms of apparent deformability, spanning a broader range of conformational states as measured by the six rigid-body parameters used to describe the spatial arrangements of the interacting bases, the root-mean-square deviations of the base-pair atoms, and the fluctuations in hydrogen-bonding geometry. The deformabilties, the modes of base-pair deformation, and the preferred sites of occurrence depend on sequence. We also characterize the positioning and overlap of the base pairs with respect to the base pairs that stack immediately above and below them in double-helical fragments. We incorporate the observed positions of the bases, base pairs, and intervening phosphorus atoms in models to predict the effects of the non-canonical interactions on overall helical structure.
Topics: Base Pairing; Databases, Nucleic Acid; Hydrogen Bonding; MicroRNAs; Models, Molecular; RNA, Double-Stranded
PubMed: 19150407
DOI: 10.1016/j.ymeth.2008.12.003 -
Nucleic Acids Research Oct 2011Hairpin loops belong to the most important structural motifs in folded nucleic acids. The d(GNA) sequence in DNA can form very stable trinucleotide hairpin loops...
Hairpin loops belong to the most important structural motifs in folded nucleic acids. The d(GNA) sequence in DNA can form very stable trinucleotide hairpin loops depending, however, strongly on the closing base pair. Replica-exchange molecular dynamics (REMD) were employed to study hairpin folding of two DNA sequences, d(gcGCAgc) and d(cgGCAcg), with the same central loop motif but different closing base pairs starting from single-stranded structures. In both cases, conformations of the most populated conformational cluster at the lowest temperature showed close agreement with available experimental structures. For the loop sequence with the less stable G:C closing base pair, an alternative loop topology accumulated as second most populated conformational state indicating a possible loop structural heterogeneity. Comparative-free energy simulations on induced loop unfolding indicated higher stability of the loop with a C:G closing base pair by ~3 kcal mol(-1) (compared to a G:C closing base pair) in very good agreement with experiment. The comparative energetic analysis of sampled unfolded, intermediate and folded conformational states identified electrostatic and packing interactions as the main contributions to the closing base pair dependence of the d(GCA) loop stability.
Topics: Base Pairing; DNA; DNA, Single-Stranded; Hydrogen Bonding; Models, Molecular; Molecular Dynamics Simulation; Nucleic Acid Conformation; Nucleotide Motifs
PubMed: 21724608
DOI: 10.1093/nar/gkr541 -
Nucleic Acids Research Nov 2022The formation of triplex DNA is a site-specific recognition method that directly targets duplex DNA. However, triplex DNA formation is generally formed for the GC and AT...
Recognition of 5-methyl-CG and CG base pairs in duplex DNA with high stability using antiparallel-type triplex-forming oligonucleotides with 2-guanidinoethyl-2'-deoxynebularine.
The formation of triplex DNA is a site-specific recognition method that directly targets duplex DNA. However, triplex DNA formation is generally formed for the GC and AT base pairs of duplex DNA, and there are no natural nucleotides that recognize the CG and TA base pairs, or even the 5-methyl-CG (5mCG) base pair. Moreover, duplex DNA, including 5mCG base pairs, epigenetically regulates gene expression in vivo, and thus targeting strategies are of biological importance. Therefore, the development of triplex-forming oligonucleotides (TFOs) with artificial nucleosides that selectively recognize these base pairs with high affinity is needed. We recently reported that 2'-deoxy-2-aminonebularine derivatives exhibited the ability to recognize 5mCG and CG base pairs in triplex formation; however, this ability was dependent on sequences. Therefore, we designed and synthesized new nucleoside derivatives based on the 2'-deoxy-nebularine (dN) skeleton to shorten the linker length connecting to the hydrogen-bonding unit in formation of the antiparallel motif triplex. We successfully demonstrated that TFOs with 2-guanidinoethyl-2'-deoxynebularine (guanidino-dN) recognized 5mCG and CG base pairs with very high affinity in all four DNA sequences with different adjacent nucleobases of guanidino-dN as well as in the promoter sequences of human genes containing 5mCG base pairs with a high DNA methylation frequency.
Topics: Humans; Base Pairing; Oligonucleotides; DNA; Deoxyribonucleosides; Nucleosides; Nucleic Acid Conformation
PubMed: 36454012
DOI: 10.1093/nar/gkac1110 -
Nucleic Acids Research Dec 2019DNA can form many structures beyond the canonical Watson-Crick double helix. It is now clear that noncanonical structures are present in genomic DNA and have biological...
DNA can form many structures beyond the canonical Watson-Crick double helix. It is now clear that noncanonical structures are present in genomic DNA and have biological functions. G-rich G-quadruplexes and C-rich i-motifs are the most well-characterized noncanonical DNA motifs that have been detected in vivo with either proscribed or postulated biological roles. Because of their independent sequence requirements, these structures have largely been considered distinct types of quadruplexes. Here, we describe the crystal structure of the DNA oligonucleotide, d(CCAGGCTGCAA), that self-associates to form a quadruplex structure containing two central antiparallel G-tetrads and six i-motif C-C+ base pairs. Solution studies suggest a robust structural motif capable of assembling as a tetramer of individual strands or as a dimer when composed of tandem repeats. This hybrid structure highlights the growing structural diversity of DNA and suggests that biological systems may harbor many functionally important non-duplex structures.
Topics: Barium; Base Pairing; Crystallography, X-Ray; DNA; Drug Stability; G-Quadruplexes; Hydrogen Bonding; Models, Molecular; Nucleic Acid Conformation; Nucleic Acid Denaturation; Nucleotide Motifs; Oligonucleotides
PubMed: 31724696
DOI: 10.1093/nar/gkz1008 -
Accounts of Chemical Research Apr 2023RNA molecules convey biological information both in their linear sequence and in their base-paired secondary and tertiary structures. Chemical probing experiments, which...
RNA molecules convey biological information both in their linear sequence and in their base-paired secondary and tertiary structures. Chemical probing experiments, which involve treating an RNA with a reagent that modifies conformationally dynamic nucleotides, have broadly enabled examination of short- and long-range RNA structure in diverse contexts, including in living cells. For decades, chemical probing experiments have been interpreted in a per-nucleotide way, such that the reactivity measured at each nucleotide reports the average structure at a position over all RNA molecules within a sample. However, there are numerous important cases where per-nucleotide chemical probing falls short, including for RNAs that are bound by proteins, RNAs that form complex higher order structures, and RNAs that sample multiple conformations.Recent experimental and computational innovations have started a revolution in RNA structure analysis by transforming chemical probing into a massively parallel, single-molecule experiment. Enabled by a specialized reverse transcription strategy called mutational profiling (MaP), multiple chemical modification events can be measured within individual RNA molecules. Nucleotides that communicate structurally through direct base pairing or large-scale folding-unfolding transitions will react with chemical probes in a correlated manner, thereby revealing structural complexity hidden to conventional approaches. These single-molecule correlated chemical probing (smCCP) experiments can be interpreted to directly identify nucleotides that base pair (the PAIR-MaP strategy) and to reveal long-range, through-space structural communication (RING-MaP). Correlated probing can also define the thermodynamic populations of complex RNA ensembles (DANCE-MaP). Complex RNA-protein networks can be interrogated by cross-linking proteins to RNA and measuring correlations between cross-linked positions (RNP-MaP).smCCP thus visualizes RNA secondary and higher-order structure with unprecedented accuracy, defining novel structures, RNA-protein interaction networks, time-resolved dynamics, and allosteric structural switches. These strategies are not mutually exclusive; in favorable cases, multiple levels of RNA structure ─ base pairing, through-space structural communication, and equilibrium ensembles ─ can be resolved concurrently. The physical experimentation required for smCCP is profoundly simple, and experiments are readily performed in cells on RNAs of any size, including large noncoding RNAs and mRNAs. Single-molecule correlated chemical probing is paving the way for a new generation of biophysical studies on RNA in living systems.
Topics: Nucleic Acid Conformation; RNA; Base Pairing; RNA, Messenger; Nucleotides; Proteins
PubMed: 36917683
DOI: 10.1021/acs.accounts.2c00782