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The co-crystal structure of the T-box tRNA-binding region, stem I, bound to tRNA is solved, showing that this region not only binds the anticodon, but also cradles the entire tRNA, forming an extended interface; the two T-loop motifs of stem I mediate interactions similar to those of RNase P and the large ribosomal subunit, even though the three species do not share a common evolutionary ancestor.

The validation and analysis of X-ray crystallographic data is essential for reproducibility and the development of crystallographic methods. Here, the authors describe a repository for crystallographic datasets and demonstrate some of the ways it could serve the crystallographic community.

Many RNAs become functional before their synthesis completes. Here the authors employ a single-molecule vectorial folding assay mimicking RNA transcription and show that the ZTP riboswitch is kinetically controlled and activated by slower unwinding and strategic pausing.

Control of gene expression at the mRNA level is used extensively by cells. Now a biomimetic strategy yields a synthetic genetic switch in which an RNA-binding protein bound at the translation start site blocks progression of the ribosome.

Structural analysis of Mango-III in complex with fluorophores reveals a globular architecture and a planar conformation of fluorophores. Structure-guided mutation and functional reselection identified two mutants with improved fluorescence intensity.

A subtle biochemical alteration can reprogram signals that herald the termination of protein translation into signals encoding amino acids at the level of messenger RNA — and without altering the corresponding DNA. See Letter p.395

Flexizyme is an in vitro evolved ribozyme which can specifically add an amino acid onto the terminal 3'OH of a tRNA. The structure of flexizyme joined to a tRNA mimic is solved. Interestingly, the RNA displays many of the known aminoacyl tRNA synthetase–tRNA interactions, approaches the tRNA in a similar manner, and exhibits an induced fit conformation that enhances specificity.

Riboswitches are RNA domains that alter gene expression in response to ligand binding. The structure of the Bacillus subtilis preQ1 ribsoswitch, which recognizes the conserved modified nucleobase preQ1, in complex with its ligand indicates how an RNA of only 34 nucleotides recognizes its ligand.

X-ray crystallography and cryo-electron microscopy analyses of Lettuce—a DNA mimic of GFP—bound to various fluorophores reveal previously unknown structures of DNA that rival analogous RNAs in complexity.

The recently discovered aptamer Beetroot is a homodimeric RNA that binds and activates DFAME, a conditional, red-shifted fluorophore derived from GFP. Here the authors determine the Beetroot-DFAME co-crystal structure, which is distinctively different from that of similar RNA aptamer Corn.

Truong et al. report crystal structures of Squash, a fluorophore-activating aptamer RNA evolved from the adenine riboswitch. Squash preserves the overall scaffold of the adenine riboswitch, yet has a highly divergent ligand-binding site.

The results of the Fifth RNA-Puzzles contest highlights advances in RNA three-dimensional structure prediction and uncovers new insights into RNA folding and structure.

The crystal structure of the fluorogenic RNA aptamer Corn reveals an unexpected homodimer. One molecule of the cognate fluorophore DFHO is encapsulated at the locally asymmetric RNA interface, which is notable for lacking intermolecular base pairs.

Structural elucidation of the RNA aptamer 'Spinach' reveals that a new G-quadruplex structure forms the fluorophore-binding site that confers the ability of the RNA to function as a GFP mimic.

The bacterial glmS riboswitch is unique in that the bound glucosamine-6-phosphate ligand acts as a cofactor for ribozyme-mediated RNA cleavage. In vitro selection and crystallographic analysis reveal that three mutations convert glmS from a cofactor-dependent to a metal ion–dependent ribozyme.

The cocrystal structure of bacterial alarmone ZMP with its cognate riboswitch reveals how the two subdomains of the latter mediate ligand recognition. Supporting biochemical analyses show that ligand binding affinity and transcription antitermination are modulated by the interdomain linker length.

A crystal structure of the RNA aptamer Mango bound to a thiazole orange–derived fluorophore reveals a three-tiered G-quadruplex structure, which, together with three flap-like nucleotides, constrains the fluorophore into its active conformation.

The structure and biological properties of RNAs are a function of changing cellular conditions. Here, Baird et al.report a high-throughput Förster resonance energy transfer (FRET) method to rapidly compare RNA structure modulation by cognate and non-cognate ligands across multiplexed solution conditions.

RNA sensors—Riboswitches—respond to the binding of small molecules ligands through structure modification. Here the authors identify synthetic small molecules that bind and regulate the activity of PreQ₁ Riboswitches despite having no obvious chemical similarity to the cognate ligand.

The first structure of a ribozyme that catalyzes the stereospecific carbon-carbon bond formation between two small molecules shows how an RNA active site can perform the synthetically important Diels-Alder reaction. Surprisingly, the ribozyme active site shares structural features with proteins that catalyze the same reaction.

c-di-GMP is a bacterial second messenger implicated in processes such as biofilm formation and switches between motile and sedentary lifestyles. The structure of the c-di-GMP–binding GEMM riboswitch is now presented with ligand and the large conformational changes between ligand-bound and unbound forms analyzed by small-angle X-ray scattering.

DHX36 is a G-quadruplex (G4) resolving helicase that targets both DNA-G4 and RNA-G4. Here the authors use single molecule FRET measurements and show that DHX36 resolves RNA-G4 structures by a mechanism involving an ATP-dependent, highly repetitive and stepwise refolding of RNA-G4 that differs from its DNA-G4 structures resolving mechanism.

The characterization of biomacromolecule structural vibrations has been impeded by a broad continuous vibrational density of states obscuring molecule specific vibrations. A terahertz microscopy system using polarization control produces signatures to dynamically fingerprint proteins and a RNA G-quadruplex.

A mechanism for the unfolding of guanine-rich DNA ‘quadruplexes’ by helicases is suggested, based on the structure of a DNA-bound helicase.

A hybrid solid–liquid phase transcription method and automated robotic platform synthesizes position-specific, fluorescence- or isotope-labelled RNA.