Analyzing and Building Nucleic Acid Structures with 3DNA

Summary

The 3DNA software package is a popular and versatile bioinformatics tool with capabilities to analyze, construct, and visualize three-dimensional nucleic acid structures. This article presents detailed protocols for a subset of new and popular features available in 3DNA, applicable to both individual structures and ensembles of related structures.

Abstract

The 3DNA software package is a popular and versatile bioinformatics tool with capabilities to analyze, construct, and visualize three-dimensional nucleic acid structures. This article presents detailed protocols for a subset of new and popular features available in 3DNA, applicable to both individual structures and ensembles of related structures. Protocol 1 lists the set of instructions needed to download and install the software. This is followed, in Protocol 2, by the analysis of a nucleic acid structure, including the assignment of base pairs and the determination of rigid-body parameters that describe the structure and, in Protocol 3, by a description of the reconstruction of an atomic model of a structure from its rigid-body parameters. The most recent version of 3DNA, version 2.1, has new features for the analysis and manipulation of ensembles of structures, such as those deduced from nuclear magnetic resonance (NMR) measurements and molecular dynamic (MD) simulations; these features are presented in Protocols 4 and 5. In addition to the 3DNA stand-alone software package, the w3DNA web server, located at http://w3dna.rutgers.edu, provides a user-friendly interface to selected features of the software. Protocol 6 demonstrates a novel feature of the site for building models of long DNA molecules decorated with bound proteins at user-specified locations.

Introduction

Understanding the three-dimensional structures of DNA, RNA, and their complexes with proteins, drugs, and other ligands, is crucial for deciphering their diverse biological functions, and for allowing the rational design of therapeutics. Exploration of such structures entails three separate, yet closely related components: analysis (to extract patterns in shapes and interactions), modeling (to assess energetics and molecular dynamics), and visualization. Structural analysis and model building are essentially two sides of the same coin, and visualization complements both of them.

The 3DNA suite of computer programs is an increasingly popular....

Protocol

1. Installation of the Software Package

1. Connect to the 3DNA website at http://x3dna.org and click the link to the 3DNA Forum. Within the Forum select the 'register' link and follow the instructions to create a new account.
2. The following instructions detail installation of the software on an OS X-based Macintosh computer with a default 'bash' shell. The procedure for Linux or Windows (Cygwin, MinGW/MSYS) systems with commonly used shells (including 'tcsh') is found within the 3DNA Forum.
3. Once you have established a user name and password, log into the Forum. Select the 'Downloads' link in th....

Results

The 3DNA software tools are routinely used to analyze nucleic acid structures. For example, the identities of base pairs and the rigid-body parameters that characterize the arrangements of bases in double-helical fragments of DNA and RNA structures are automatically computed and stored for each new entry in the Nucleic Acid Database²², a worldwide repository of nucleic acid structural information. The values of the rigid-body parameters determined with Protocol 2 readily reveal distortions in three-dimensional.......

Discussion

The set of protocols presented in this article only touch upon the capabilities of the 3DNA suite of programs. The tools can be applied to RNA structures to identify non-canonical base pairs, to determine the secondary structural contexts in which such pairing occurs, to quantify the spatial disposition of helical fragments, to measure the overlap of bases along the chain backbone, etc. The rebuild command allows the user to construct simple and informative block representations of the bases and base pairs like that show.......