Nucleic acid double helices in their DNA, RNA, and DNA-RNA hybrid form play a fundamental role in biology and are main building blocks of artificial nanostructures, but how their properties depend on temperature remains poorly understood. Here, we report thermal dependence of dynamic bending persistence length, twist rigidity, stretch modulus, and twist-stretch coupling for DNA, RNA, and hybrid duplexes between 7°C and 47°C. The results are based on all-atom molecular dynamics simulations using different force field parameterizations. We first demonstrate that unrestrained molecular dynamics can reproduce experimentally known mechanical properties of the duplexes at room temperature. Beyond experimentally known features, we also infer the twist rigidity and twist-stretch coupling of the hybrid duplex. As for the temperature dependence, we found that increasing temperature softens all the duplexes with respect to bending, twisting, and stretching. The relative decrease of the stretch moduli is 0.003-0.004/°C, similar for all the duplex variants despite their very different stretching stiffness, whereas RNA twist stiffness decreases by 0.003/°C, and smaller values are found for the other elastic moduli. The twist-stretch couplings are nearly unaffected by temperature. The stretching, bending, and twisting stiffness all include an important entropic component. Relation of our results to the two-state model of DNA flexibility is discussed. Our work provides temperature-dependent elasticity of nucleic acid duplexes at the microsecond scale relevant for initial stages of protein binding.

• MeSH
• DNA * chemie   MeSH
• konformace nukleové kyseliny MeSH
• pružnost MeSH
• RNA * chemie   MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA * MeSH
• RNA * MeSH

With both catalytic and genetic functions, ribonucleic acid (RNA) is perhaps the most pluripotent chemical species in molecular biology, and its functions are intimately linked to its structure and dynamics. Computer simulations, and in particular atomistic molecular dynamics (MD), allow structural dynamics of biomolecular systems to be investigated with unprecedented temporal and spatial resolution. We here provide a comprehensive overview of the fast-developing field of MD simulations of RNA molecules. We begin with an in-depth, evaluatory coverage of the most fundamental methodological challenges that set the basis for the future development of the field, in particular, the current developments and inherent physical limitations of the atomistic force fields and the recent advances in a broad spectrum of enhanced sampling methods. We also survey the closely related field of coarse-grained modeling of RNA systems. After dealing with the methodological aspects, we provide an exhaustive overview of the available RNA simulation literature, ranging from studies of the smallest RNA oligonucleotides to investigations of the entire ribosome. Our review encompasses tetranucleotides, tetraloops, a number of small RNA motifs, A-helix RNA, kissing-loop complexes, the TAR RNA element, the decoding center and other important regions of the ribosome, as well as assorted others systems. Extended sections are devoted to RNA-ion interactions, ribozymes, riboswitches, and protein/RNA complexes. Our overview is written for as broad of an audience as possible, aiming to provide a much-needed interdisciplinary bridge between computation and experiment, together with a perspective on the future of the field.

• MeSH
• DNA chemie   MeSH
• katalýza MeSH
• konformace nukleové kyseliny * MeSH
• počítačová simulace MeSH
• RNA chemie   MeSH
• simulace molekulární dynamiky * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• DNA MeSH
• RNA MeSH

We present a systematic study of the long-timescale dynamics of the Drew-Dickerson dodecamer (DDD: d(CGCGAATTGCGC)2) a prototypical B-DNA duplex. Using our newly parameterized PARMBSC1 force field, we describe the conformational landscape of DDD in a variety of ionic environments from minimal salt to 2 M Na(+)Cl(-) or K(+)Cl(-) The sensitivity of the simulations to the use of different solvent and ion models is analyzed in detail using multi-microsecond simulations. Finally, an extended (10 μs) simulation is used to characterize slow and infrequent conformational changes in DDD, leading to the identification of previously uncharacterized conformational states of this duplex which can explain biologically relevant conformational transitions. With a total of more than 43 μs of unrestrained molecular dynamics simulation, this study is the most extensive investigation of the dynamics of the most prototypical DNA duplex.

• MeSH
• B-DNA chemie   ultrastruktura   MeSH
• chlorid draselný chemie   MeSH
• chlorid sodný chemie   MeSH
• konformace nukleové kyseliny * MeSH
• molekulární modely MeSH
• simulace molekulární dynamiky * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• B-DNA MeSH
• chlorid draselný MeSH
• chlorid sodný MeSH

Double stranded helical DNA and RNA are flexible molecules that can undergo global conformational fluctuations. Their bending, twisting and stretching deformabilities are of similar magnitude. However, recent single-molecule experiments revealed a striking qualitative difference indicating an opposite sign for the twist-stretch couplings of dsDNA and dsRNA [Lipfert et al. 2014. Proc. Natl. Acad. Sci. U.S.A. 111, 15408] that is not explained by existing models. Employing unconstrained Molecular Dynamics (MD) simulations we are able to reproduce the qualitatively different twist-stretch coupling for dsDNA and dsRNA in semi-quantitative agreement with experiment. Similar results are also found in simulations that include an external torque to induce over- or unwinding of DNA and RNA. Detailed analysis of the helical deformations coupled to twist indicate that the interplay of helical rise, base pair inclination and displacement from the helix axis upon twist changes are responsible for the different twist-stretch correlations. Overwinding of RNA results in more compact conformations with a narrower major groove and consequently reduced helical extension. Overwinding of DNA decreases the size of the minor groove and the resulting positive base pair inclination leads to a slender and more extended helical structure.

• MeSH
• biomechanika MeSH
• DNA chemie   MeSH
• dvouvláknová RNA chemie   MeSH
• konformace nukleové kyseliny MeSH
• párování bází MeSH
• simulace molekulární dynamiky MeSH
• točivý moment MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• DNA MeSH
• dvouvláknová RNA MeSH

A-tracts are functionally important DNA sequences which induce helix bending and have peculiar structural properties. While A-tract structure has been qualitatively well characterized, their mechanical properties remain controversial. A-tracts appear structurally rigid and resist nucleosome formation, but seem flexible in DNA looping. In this work, we investigate mechanical properties of symmetric AnTn and asymmetric A2n tracts for n = 3, 4, 5 using two types of coarse-grained models. The first model represents DNA as an ensemble of interacting rigid bases with non-local quadratic deformation energy, the second one treats DNA as an anisotropically bendable and twistable elastic rod. Parameters for both models are inferred from microsecond long, atomic-resolution molecular dynamics simulations. We find that asymmetric A-tracts are more rigid than the control G/C-rich sequence in localized distortions relevant for nucleosome formation, but are more flexible in global bending and twisting relevant for looping. The symmetric tracts, in contrast, are more rigid than asymmetric tracts and the control, both locally and globally. Our results can reconcile the contradictory stiffness data on A-tracts and suggest symmetric A-tracts to be more efficient in nucleosome exclusion than the asymmetric ones. This would open a new possibility of gene expression manipulation using A-tracts.

• MeSH
• adenin chemie   MeSH
• biomechanika MeSH
• DNA chemie   MeSH
• entropie MeSH
• konformace nukleové kyseliny MeSH
• nukleozomy chemie   MeSH
• poly A chemie   MeSH
• sekvence nukleotidů MeSH
• simulace molekulární dynamiky MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenin MeSH
• DNA MeSH
• nukleozomy MeSH
• poly A MeSH

The L1 stalk is a key mobile element of the large ribosomal subunit which interacts with tRNA during translocation. Here, we investigate the structure and mechanical properties of the rRNA H76/H75/H79 three-way junction at the base of the L1 stalk from four different prokaryotic organisms. We propose a coarse-grained elastic model and parameterize it using large-scale atomistic molecular dynamics simulations. Global properties of the junction are well described by a model in which the H76 helix is represented by a straight, isotropically flexible elastic rod, while the junction core is represented by an isotropically flexible spherical hinge. Both the core and the helix contribute substantially to the overall H76 bending fluctuations. The presence of wobble pairs in H76 does not induce any increased flexibility or anisotropy to the helix. The half-closed conformation of the L1 stalk seems to be accessible by thermal fluctuations of the junction itself, without any long-range allosteric effects. Bending fluctuations of H76 with a bulge introduced in it suggest a rationale for the precise position of the bulge in eukaryotes. Our elastic model can be generalized to other RNA junctions found in biological systems or in nanotechnology.

• MeSH
• biomechanika MeSH
• konformace nukleové kyseliny MeSH
• ribozomální proteiny chemie   MeSH
• RNA ribozomální 23S chemie   MeSH
• simulace molekulární dynamiky MeSH
• velké podjednotky ribozomu archebakteriální chemie   MeSH
• velké podjednotky ribozomu bakteriální chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ribosomal protein L1 MeSH Prohlížeč
• ribozomální proteiny MeSH
• RNA ribozomální 23S MeSH

We present extensive explicit solvent molecular dynamics analysis of three RNA three-way junctions (3WJs) from the large ribosomal subunit: the 3WJ formed by Helices 90-92 (H90-H92) of 23S rRNA; the 3WJ formed by H42-H44 organizing the GTPase associated center (GAC) of 23S rRNA; and the 3WJ of 5S rRNA. H92 near the peptidyl transferase center binds the 3'-CCA end of amino-acylated tRNA. The GAC binds protein factors and stimulates GTP hydrolysis driving protein synthesis. The 5S rRNA binds the central protuberance and A-site finger (ASF) involved in bridges with the 30S subunit. The simulations reveal that all three 3WJs possess significant anisotropic hinge-like flexibility between their stacked stems and dynamics within the compact regions of their adjacent stems. The A-site 3WJ dynamics may facilitate accommodation of tRNA, while the 5S 3WJ flexibility appears to be essential for coordinated movements of ASF and 5S rRNA. The GAC 3WJ may support large-scale dynamics of the L7/L12-stalk region. The simulations reveal that H42-H44 rRNA segments are not fully relaxed and in the X-ray structures they are bent towards the large subunit. The bending may be related to L10 binding and is distributed between the 3WJ and the H42-H97 contact.

• MeSH
• archeální RNA chemie   MeSH
• bakteriální RNA chemie   MeSH
• Escherichia coli genetika   MeSH
• fosfáty chemie   MeSH
• Haloarcula marismortui genetika   MeSH
• konformace nukleové kyseliny MeSH
• RNA ribozomální 23S chemie   MeSH
• RNA ribozomální 5S chemie   MeSH
• simulace molekulární dynamiky MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• archeální RNA MeSH
• bakteriální RNA MeSH
• fosfáty MeSH
• RNA ribozomální 23S MeSH
• RNA ribozomální 5S MeSH

A method is proposed to measure global bending in DNA and RNA structures. It relies on a properly defined averaging of base-fixed coordinate frames, computes mean frames of suitably chosen groups of bases and uses these mean frames to evaluate bending. The method is applied to DNA A-tracts, known to induce considerable bend to the double helix. We performed atomistic molecular dynamics simulations of sequences containing the A(4)T(4) and T(4)A(4) tracts, in a single copy and in two copies phased with the helical repeat. Various temperature and salt conditions were investigated. Our simulations indicate bending by roughly 10 degrees per A(4)T(4) tract into the minor groove, and an essentially straight structure containing T(4)A(4), in agreement with electrophoretic mobility data. In contrast, we show that the published NMR structures of analogous sequences containing A(4)T(4) and T(4)A(4) tracts are significantly bent into the minor groove for both sequences, although bending is less pronounced for the T(4)A(4) containing sequence. The bending magnitudes obtained by frame averaging are confirmed by the analysis of superhelices composed of repeated tract monomers.

• MeSH
• adenin chemie   MeSH
• DNA chemie   MeSH
• konformace nukleové kyseliny MeSH
• RNA chemie   MeSH
• simulace molekulární dynamiky MeSH
• thymin chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenin MeSH
• DNA MeSH
• RNA MeSH
• thymin MeSH

Unrestrained 5-20-ns explicit-solvent molecular dynamics simulations using the Cornell et al. force field have been carried out for d[GCG(N)11GCG]2 (N, purine base) considering guanine*cytosine (G*C), adenine*thymine (A*T), inosine*5-methyl-cytosine (I*mC), and 2-amino-adenine*thymine (D*T) basepairs. The simulations unambiguously show that the structure and elasticity of N-tracts is primarily determined by the presence of the amino group in the minor groove. Simulated A-, I-, and AI-tracts show almost identical structures, with high propeller twist and minor groove narrowing. G- and D-tracts have small propeller twisting and are partly shifted toward the A-form. The elastic properties also differ between the two groups. The sequence-dependent electrostatic component of base stacking seems to play a minor role. Our conclusions are entirely consistent with available experimental data. Nevertheless, the propeller twist and helical twist in the simulated A-tract appear to be underestimated compared to crystallographic studies. To obtain further insight into the possible force field deficiencies, additional multiple simulations have been made for d(A)10, systematically comparing four major force fields currently used in DNA simulations and utilizing B and A-DNA forms as the starting structure. This comparison shows that the conclusions of the present work are not influenced by the force field choice.

• MeSH
• DNA chemie   MeSH
• konformace nukleové kyseliny MeSH
• molekulární modely MeSH
• párování bází MeSH
• polydeoxyribonukleotidy chemie   MeSH
• pružnost MeSH
• puriny chemie   MeSH
• vodíková vazba MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA MeSH
• polydeoxyribonukleotidy MeSH
• puriny MeSH

The crystal structure of d(CATGGGCCCATG)(2) shows unique stacking patterns of a stable B<-->A-DNA intermediate. We evaluated intrinsic base stacking energies in this crystal structure using an ab initio quantum mechanical method. We found that all crystal base pair steps have stacking energies close to their values in the standard and crystal B-DNA geometries. Thus, naturally occurring stacking geometries were essentially isoenergetic while individual base pair steps differed substantially in the balance of intra-strand and inter-strand stacking terms. Also, relative dispersion, electrostatic and polarization contributions to the stability of different base pair steps were very sensitive to base composition and sequence context. A large stacking flexibility is most apparent for the CpA step, while the GpG step is characterized by weak intra-strand stacking. Hydration effects were estimated using the Langevin dipoles solvation model. These calculations showed that an aqueous environment efficiently compensates for electrostatic stacking contributions. Finally, we have carried out explicit solvent molecular dynamics simulation of the d(CATGGGCCCATG)(2) duplex in water. Here the DNA conformation did not retain the initial crystal geometry, but moved from the B<-->A intermediate towards the B-DNA structure. The base stacking energy improved in the course of this simulation. Our findings indicate that intrinsic base stacking interactions are not sufficient to stabilize the local conformational variations in crystals.

• MeSH
• DNA chemie   genetika   metabolismus   MeSH
• krystalizace MeSH
• molekulární modely MeSH
• ohebnost (fyzika) MeSH
• párování bází * MeSH
• počítačová simulace * MeSH
• rozpouštědla MeSH
• sekvence nukleotidů MeSH
• statická elektřina MeSH
• termodynamika MeSH
• voda chemie   metabolismus   MeSH
• zastoupení bazí MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• DNA MeSH
• rozpouštědla MeSH
• voda MeSH