More than Proton Detection—New Avenues for NMR Spectroscopy of RNA
This minireview written by Harald Schwalbe, Boris Fürtig and coworkers reports on the development of NMR methods that utilize detection on low-g nuclei (heteronuclei like 13C or 15N with lower gyromagnetic ratio than 1H) to obtain unique structural and dynamic information for large RNA molecules in solution. Experiments involve through-bond correlations of nucleobases and the phosphodiester backbone of RNA for chemical shift assignment and make information on hydrogen bonding uniquely accessible. Previously unobservable NMR resonances of amino groups in RNA nucleobases are now detected in experiments involving conformational exchange-resistant double-quantum 1H coherences, detected by 13C NMR spectroscopy. Furthermore, 13C and 15N chemical shifts provide valuable information on conformations. All the covered aspects point to the advantages of low-g nuclei detection experiments in RNA.
Principles for Integrative Structural Biology Studies
Guru of integrative structural biology computation Andrej Sali and Michale P. Rout summarize in the recent Cell Primer Principles for Integrative Structural Biology Studies.
Integrative Structural Biology of Protein-RNA Complexes
Ribonucleoprotein complexes (RNPs) are central to all processes in the cell. One of the prerequisites to understand how RNPs work is to determine their high-resolution structures. With the recent revolution in cryo-electron microscopy this task has become easier for large RNP machines, such as ribosomes, spliceosomes, and polymerases. However, the transient and highly dynamic nature of many RNPs makes structure determination a challenging task. Thus, an integrative structural and molecular biology approach is required, tackling three key challenges: (1) identification of cognate RNA sequences; (2) collection of structural data by conducting X-ray crystallography, NMR, electron microscopy, small-angle scattering (SAS), and other experiments; and (3) the creation of structural models that integrates all experimental restraints. Given the breadth of expertise required, Janosch Henning et. al. in Structure present an overview of available methods and successful examples with the goal to provide readers with a selection of promising options for structure determination of RNPs.
Structural biology of cell surface receptor-ligand interactions
Plants have evolved unique membrane receptors that interpret native and foreign cues to coordinate plant life and adaptation. This large family of receptor proteins have evolved very diverse ectodomains, acquiring the capacity to sense ligands of very different chemical nature. A mechanistic understanding on how these signaling systems work will help to comprehend and unveil key cell biology questions. The review by Steven Moussou and Julia Santiago in Current Opinion in Plant Biology aims to focus on the latest receptor-ligands interactions and regulatory mechanism that have been structurally characterized, as well as new receptor folds.
Challenges and perspectives for structural biology of lncRNAs-the example of the Xist lncRNA A-repeats
Following the discovery of numerous long non-coding RNA (lncRNA) transcripts in the human genome, their important roles in biology and human disease are emerging. Recent progress in experimental methods has enabled the identification of structural features of lncRNAs. However, determining high-resolution structures is challenging as lncRNAs are expected to be dynamic and adopt multiple conformations, which may be modulated by interaction with protein binding partners. The X-inactive specific transcript (Xist) is necessary for X inactivation during dosage compensation in female placental mammals and one of the best-studied lncRNAs. Recent progress has provided new insights into the domain organization, molecular features, and RNA binding proteins that interact with distinct regions of Xist. The A-repeats located at the 5' end of the transcript are of particular interest as they are essential for mediating silencing of the inactive X chromosome. In this review, recent progress with elucidating structural features of the Xist lncRNA, focusing on the A-repeats is discussed. The experimental and computational approaches employed that have led to distinct structural models, likely reflecting the intrinsic dynamics of this RNA are overviewed. The presence of multiple dynamic conformations may also play an important role in the formation of the associated RNPs, thus influencing the molecular mechanism underlying the biological function of the Xist A-repeats. Alisha Jones and Michael Sattler in Journal of Molecular Cell Biology propose that integrative approaches that combine biochemical experiments and high-resolution structural biology in vitro with chemical probing and functional studies in vivo are required to unravel the molecular mechanisms of lncRNAs.