Molecular dynamics simulation and binding energy calculation for estimation of oligonucleotide duplex thermostability in RNA-based therapeutics

Comparison of interaction between antimiR and microRNA versus HDO-antimiR and microRNA by molecular dynamics simulation

Recently, we found DNA/RNA heteroduplex oligonucleotide-based antimiR (HDO-antimiR) can more efficiently inhibit the target miRNA than conventional antimiR after its cellular uptake. But the mechanism of HDO-antimiR about the target-silencing is unknown. We here tried to elucidate the interaction mechanism of HDO-antimiR to miRNA using molecular dynamics (MD) simulation. When interaction of the conventional antimiR or HDO-antimiR and the target miRNA was simulated, they combined with each other in various forms. In the hydrogen bond analyses, base site of the antimiR formed hydrogen bond with miRNA. On the other hand, phosphate site of the HDO-antimiR formed hydrogen bond with miRNA. These results suggested that there were differences about the binding mechanisms between antimiR and HDO-antimiR to the target miRNA. In particular, there was a difference in the binding site between antimiR and HDO-antimiR. Additionally, it was found that guanine in the miRNA is mainly involved in the binding to the antimiR or HDO-antimiR. MD simulation method is useful in understanding the mechanism of oligonucleotide therapeutics.

Research in the Field of Drug Design and Development

The processes used by academic and industrial scientists to discover new drugs have recently experienced a true renaissance, with many new and exciting techniques being developed over the past 5-10 years alone. Drug design and discovery, and the search for new safe and well-tolerated compounds, as well as the ineffectiveness of existing therapies, and society's insufficient knowledge concerning the prophylactics and pharmacotherapy of the most common diseases today, comprise a serious challenge. This can influence not only the quality of human life, but also the health of whole societies, which became evident during the COVID-19 pandemic. In general, the process of drug development consists of three main stages: drug discovery, preclinical development using cell-based and animal models/tests, clinical trials on humans and, finally, forward moving toward the step of obtaining regulatory approval, in order to market the potential drug. In this review, we will attempt to outline the first three most important consecutive phases in drug design and development, based on the experience of three cooperating and complementary academic centers of the Visegrád group; i.e., Medical University of Lublin, Poland, Masaryk University of Brno, Czech Republic, and Comenius University Bratislava, Slovak Republic.

Structure-Dependent Eco-Toxicity of Vegetable Tannin

Vegetable tannin is widely applied in various industries, in agriculture, and in water treatment as a natural polyphenolic compound; however, little data has been collected concerning the relationship between structure and eco-toxicity. Here, the toxicity of six commercial tannin and three model chemicals was assessed using Photobacterium phosphoreum. Two kinds of hydrolyzed tannin displayed higher bioluminescence inhibition than four kinds of condensed tannin, and the model chemical of hydrolyzed tannin also showed greater toxicity than those of condensed tannin, indicating the structure dependent eco-toxicity of vegetable tannin. The reactive toxicity mechanism was proposed, which was illustrated by molecular simulations based on the model chemicals and luciferase.

Calculation of Energy for RNA/RNA and DNA/RNA Duplex Formation by Molecular Dynamics Simulation

Abstract

The development of approaches for predictive calculation of hybridization properties of various nucleic acid (NA) derivatives is the basis for the rational design of the NA-based constructs. Modern advances in computer modeling methods provide the feasibility of these calculations. We have analyzed the possibility of calculating the energy of DNA/RNA and RNA/RNA duplex formation using representative sets of complexes (65 and 75 complexes, respectively). We used the classical molecular dynamics (MD) method, the MMPBSA or MMGBSA approaches to calculate the enthalpy (ΔH°) component, and the quasi-harmonic approximation (Q-Harm) or the normal mode analysis (NMA) methods to calculate the entropy (ΔS°) contribution to the Gibbs energy ($$\Delta G_{{37}}^{^\circ }$$ ) of the NA complex formation. We have found that the MMGBSA method in the analysis of the MD trajectory of only the NA duplex and the empirical linear approximation allow calculation of the enthalpy of formation of the DNA, RNA, and hybrid duplexes of various lengths and GC content with an accuracy of 8.6%. Within each type of complex, the combination of rather efficient MMGBSA and Q-Harm approaches being applied to the trajectory of only the bimolecular complex makes it possible to calculate the $$\Delta G_{{37}}^{^\circ }$$ of the duplex formation with an error value of 10%. The high accuracy of predictive calculation for different types of natural complexes (DNA/RNA, DNA/RNA, and RNA/RNA) indicates the possibility of extending the considered approach to analogs and derivatives of nucleic acids, which gives a fundamental opportunity in the future to perform rational design of new types of NA-targeted sequence-specific compounds.

Molecular Dynamics Study of the Hybridization between RNA and Modified Oligonucleotides

MicroRNAs (miRNAs) are attractive drug candidates for many diseases as they can modulate the expression of gene networks. Recently, we discovered that DNAs targeting microRNA-22-3p (miR-22-3p) hold the potential for treating obesity and related metabolic disorders (type 2 diabetes mellitus, hyperlipidemia, and nonalcoholic fatty liver disease (NAFLD)) by turning fat-storing white adipocytes into fat-burning adipocytes. In this work, we explored the effects of chemical modifications, including phosphorothioate (PS), locked nucleic acid (LNA), and peptide nucleic acid (PNA), on the structure and energy of DNA analogs by using molecular dynamics (MD) simulations. To achieve a reliable prediction of the hybridization free energy, the AMOEBA polarizable force field and the free energy perturbation technique were employed. The calculated hybridization free energies are generally compatible with previous experiments. For LNA and PNA, the enhanced duplex stability can be explained by the preorganization mechanism, i.e., the single strands adopt stable helical structures similar to those in the duplex. For PS, the S and R isomers (Sp and Rp) have preferences for C2'-endo and C3'-endo sugar puckering conformations, respectively, and therefore Sp is less stable than Rp in DNA/RNA hybrids. In addition, the solvation penalty of Rp accounts for its destabilization effect. PS-LNA is similar to LNA as the sugar puckering is dominated by the locked sugar ring. This work demonstrated that MD simulations with polarizable force fields are useful for the understanding and design of modified nucleic acids.

Chemical Modification of the siRNA Seed Region Suppresses Off-Target Effects by Steric Hindrance to Base-Pairing with Targets

Chemical modifications of 2'-O-methyl (2'-OMe) and locked nucleic acid (LNA) of the nucleotides in the seed region (positions 2-8) of the small interfering RNA (siRNA) guide strand significantly reduced seed-matched (SM) off-target effects. The siRNA with 2'-OMe modifications inhibited the expression of a completely-matched (CM) target gene, whereas that with LNA modifications did not inhibit the expression of the CM target. By computational predictions of conformational changes of siRNA by these modifications, we revealed that both modifications in the siRNA seed region reduce SM off-target effects by steric hindrance to base-pairing with target transcripts but LNA modifications also disturb the association of the siRNA guide strand with the Argonaute (AGO) protein by altering RNA conformation. Thus, chemical modifications of the siRNA guide strand, which alter steric conformation to disturb base-pairing with target transcripts but do not disturb the association with the AGO protein, may successfully suppress off-target effects without substantial loss of RNA silencing activity.

Evaluation of the Gibbs Free Energy Changes and Melting Temperatures of DNA/DNA Duplexes Using Hybridization Enthalpy Calculated by Molecular Dynamics Simulation

A molecular dynamics simulation approach was applied for the prediction of the thermal stability of oligonucleotide duplexes. It was shown that the enthalpy of the DNA/DNA complex formation could be calculated using this approach. We have studied the influence of various simulation parameters on the secondary structure and the hybridization enthalpy value of Dickerson-Drew dodecamer. The optimal simulation parameters for the most reliable prediction of the enthalpy values were determined. The thermodynamic parameters (enthalpy and entropy changes) of a duplex formation were obtained experimentally for 305 oligonucleotides of various lengths and GC-content. The resulting database was studied with molecular dynamics (MD) simulation using the optimized simulation parameters. Gibbs free energy changes and the melting temperatures were evaluated using the experimental correlation between enthalpy and entropy changes of the duplex formation and the enthalpy values calculated by the MD simulation. The average errors in the predictions of enthalpy, the Gibbs free energy change, and the melting temperature of oligonucleotide complexes were 11%, 10%, and 4.4 °C, respectively. We have shown that the molecular dynamics simulation gives a possibility to calculate the thermal stability of native DNA/DNA complexes a priori with an unexpectedly high accuracy.

Stacking in RNA: NMR of Four Tetramers Benchmark Molecular Dynamics

Molecular dynamics (MD) simulations for RNA tetramers r(AAAA), r(CAAU), r(GACC), and r(UUUU) are benchmarked against 1H-1H NOESY distances and 3J scalar couplings to test effects of RNA torsion parametrizations. Four different starting structures were used for r(AAAA), r(CAAU), and r(GACC), while five starting structures were used for r(UUUU). On the basis of X-ray structures, criteria are reported for quantifying stacking. The force fields, AMBER ff99, parmbsc0, parm99χ_Yil, ff10, and parmTor, all predict experimentally unobserved stacks and intercalations, e.g., base 1 stacked between bases 3 and 4, and incorrect χ, ϵ, and sugar pucker populations. The intercalated structures are particularly stable, often lasting several microseconds. Parmbsc0, parm99χ_Yil, and ff10 give similar agreement with NMR, but the best agreement is only 46%. Experimentally unobserved intercalations typically are associated with reduced solvent accessible surface area along with amino and hydroxyl hydrogen bonds to phosphate nonbridging oxygens. Results from an extensive set of MD simulations suggest that recent force field parametrizations improve predictions, but further improvements are necessary to provide reasonable agreement with NMR. In particular, intramolecular stacking and hydrogen bonding interactions may not be well balanced with the TIP3P water model. NMR data and the scoring method presented here provide rigorous benchmarks for future changes in force fields and MD methods.

Probing the relationship between anti-Pneumocystis carinii activity and DNA binding of bisamidines by molecular dynamics simulations

The anti-Pneumocystis carinii activity of 13 synthetic pentamidine analogs was analyzed. The experimental differences in melting points of DNA dodecamer 5'-(CGCGAATTCGCG)₂-3' complexes (ΔT_m), and in the biological activity measured using ATP bioluminescence assay (IC₅₀) together with the theoretical free energy of DNA-ligand binding estimated by the proposed computational protocol, showed that the experimental activity of the tested pentamidines appeared to be due to the binding to the DNA minor groove with extended AT sequences. The effect of heteroatoms in the aliphatic linker, and the sulfonamide or methoxy substituents on the compound inducing changes in the interactions with the DNA minor groove was examined and was correlated with biological activity. In computational analysis, the explicit solvent approximation with the discrete water molecules was taken into account, and the role of water molecules in the DNA-ligand complexes was defined.

The impact of molecular dynamics on drug design: applications for the characterization of ligand-macromolecule complexes

Among all tools available to design new drugs, molecular dynamics (MD) simulations have become an essential technique. Initially developed to investigate molecular models with a limited number of atoms, computers now enable investigations of large macromolecular systems with a simulation time reaching the microsecond range. The reviewed articles cover four years of research to give an overview on the actual impact of MD on the current medicinal chemistry landscape with a particular emphasis on studies of ligand-protein interactions. With a special focus on studies combining computational approaches with data gained from other techniques, this review shows how deeply embedded MD simulations are in drug design strategies and articulates what the future of this technique could be.

Cooperative gene regulation by microRNA pairs and their identification using a computational workflow

MicroRNAs (miRNAs) are an integral part of gene regulation at the post-transcriptional level. Recently, it has been shown that pairs of miRNAs can repress the translation of a target mRNA in a cooperative manner, which leads to an enhanced effectiveness and specificity in target repression. However, it remains unclear which miRNA pairs can synergize and which genes are target of cooperative miRNA regulation. In this paper, we present a computational workflow for the prediction and analysis of cooperating miRNAs and their mutual target genes, which we refer to as RNA triplexes. The workflow integrates methods of miRNA target prediction; triplex structure analysis; molecular dynamics simulations and mathematical modeling for a reliable prediction of functional RNA triplexes and target repression efficiency. In a case study we analyzed the human genome and identified several thousand targets of cooperative gene regulation. Our results suggest that miRNA cooperativity is a frequent mechanism for an enhanced target repression by pairs of miRNAs facilitating distinctive and fine-tuned target gene expression patterns. Human RNA triplexes predicted and characterized in this study are organized in a web resource at www.sbi.uni-rostock.de/triplexrna/.

Bi and tri-substituted phenyl rings containing bisbenzimidazoles bind differentially with DNA duplexes: a biophysical and molecular simulation study

Recently synthesis of programmable DNA ligands which can regulate transcription factors have increased the interest of researchers on the functional ability of DNA interacting compounds. A series of DNA interacting compounds are being designed which can differentiate between GC and AT rich DNA. In this study, we have studied the specificity of a few novel bisbenzimidazoles having different bi/tri-substituted phenyl rings, with DNA duplexes using spectroscopic methods. This study entails an integrative approach where we combine biophysical methods and molecular dynamics simulation studies to establish suitable scaffolds to target A/T DNA. We have designed a few analogues of Hoechst 33342 viz.; dimethoxy (DMA), trimethoxy (TMA), dichloro (DCA) and difluoro (DFA) functionalities and performed molecular docking of newly designed analogues with biologically relevant AT and GC rich DNA sequences. The docking studies, along with molecular dynamics (MD) simulations of d(ATATATATATATATAT)2, d(GA4T4C)2, d(GT4A4C)2 and GC rich sequence: d(GCGCGCGCGCGCGCGC)2 complexed with DMA, TMA and DFA, showed that these molecules have higher binding affinity towards AT rich DNA. None of these compounds exhibited an affinity to GC rich DNA rather we observed that these compounds destabilize GC rich DNA. The binding was characterized by strong stabilization of the polynucleotides against thermal strand separation in thermal melting experiments. New insights into the molecules binding to DNA have emerged from these studies. All the DNA binding ligands stabilized d(GA4T4C)2 and d(GT4A4C)2 more out of the five oligomers used for the study, suggesting that these ligands bind 'A4T4' and 'T4A4' strongly as compared to 'ATAT' base pairs.

Biological activity and biotechnological aspects of locked nucleic acids

Locked nucleic acid (LNA) is one of the most promising new nucleic acid analogues that has been produced under the past two decades. In this chapter, we have tried to cover many of the different areas, where this molecule has been used to improve the function of synthetic oligonucleotides (ONs). The use of LNA in antisense ONs, including gapmers, splice-switching ONs, and siLNA, as well as antigene ONs, is reviewed. Pharmacokinetics as well as pharmacodynamics of LNA ONs and a description of selected compounds in, or close to, clinical testing are described. In addition, new LNA modifications and the adaptation of enzymes for LNA incorporation are reviewed. Such enzymes may become important for the development of stabilized LNA-containing aptamers.