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The condensation of repeat-containing RNAs can have neurotoxic effects but is challenging to study. Now a NMR approach termed condensate detection by semi-solid magnetization transfer (CONDENSE-MT) can be used to study RNA condensate dynamics, proton–solvent exchange kinetics and condensate hydration.

The authors report an unusual mode of AU-rich RNA recognition by the RNA recognition motifs of DND1, a protein essential for germline development, in a 27.5 kDa NMR structure and provide additional insight on DND1 function from cell-based experiments.

X-ray ptychography has been used to extend the field of view in high-resolution quantitative imaging. Godardet al. develop Bragg-mode ptychography to reconstruct, in three dimensions, a crystalline specimen that is too large to be studied as a single object with a coherence-limited X-ray beam.

A novel combined NMR and EPR spectroscopy approach reveals the structure and assembly mechanism of a 70-kDa bacterial ribonucleoprotein complex acting as a protein sponge in translational regulation.

Some cholesterol-lowering drugs can increase the risk of type 2 diabetes, but the mechanism behind this is not fully understood. Here the authors show that there is a single genetic regulatory module that influences both cholesterol levels and glucose levels, providing a link between cholesterol levels and diabetes.

REDEFINE is a label-free approach for characterizing biomolecular condensates based on NMR diffusion experiments, determining parameters of biphasic condensates, namely partitioning, diffusion coefficients, droplet size, permeability, and chemical exchange.

A nuclear magnetic resonance spectroscopy-based approach to monitor multiple molecule and reaction types at once, Systems NMR, provides in vitro insights into complex biomolecular network dynamics.

NMR and Raman spectroscopies pinpoint the role of the protein droplet surface and RNA in the liquid droplet maturation mechanism of the FUS protein. A crust-like β-sheet structure is formed on the surface of FUS droplets during aging.

The function of GW182 proteins in miRNA-mediated gene silencing has been unclear. Studies in human and fly cells now identify tryptophan-containing motifs as important repressive elements. These motifs, which are dispersed throughout GW182 proteins, function additively by recruiting deadenylase complexes to repress both poly(A)⁺ and poly(A)⁻ mRNAs, suggesting that recruitment, in addition to catalyzing deadenylation, also mediates translational repression.

An agarose hydrogel mimicking cytoskeleton stabilizes protein liquid droplets and enables precise quantification of protein percentage in phase-separated droplets and in the dispersed phases as well as intramolecular distances via NMR and EPR.

Mutations in the RNA binding protein FUS cause amyotrophic lateral sclerosis (ALS). Here the authors characterize FUS-binding to U1 snRNP and show that ALS-associated FUS aberrantly contacts U1 snRNA which interferes with its biogenesis pathway.

An integrated structural biology approach is utilized to elucidate the solution structure of the polypyrimidine-tract binding protein 1 (PTBP1/hnRNP I) complexed with an internal ribosome entry site (IRES) RNA fragment from encephalomyocarditis virus (EMCV).

Bacteria use alternative sigma factors to direct transcription initiation from new sets of gene promoters in response to environmental stress. Complementary structural and biochemical analyses now reveal a new promoter-recognition mechanism that is the basis for the altered promoter specificity conferred by stress-responsive sigma factors.

RBM39 is an essential splicing factor for several cancer cells. Here, the authors described how RBM39 selects RNA at atomic level and autoregulates at the mRNA level by selecting the 3’-splice site of a poison exon.

The RNA Recognition Motif (RRM) is the most ubiquitous RNA binding domain. Here the authors combined NMR and molecular dynamics simulations and show that the RRM RNA binding surface exists in different states and that a conformational switch of aromatic side-chains fine-tunes sequence specific binding affinities.

SRSF1 is an oncoprotein that plays important roles in RNA metabolism. We reveal the structure of the human SRSF1 RRM1 bound to RNA, and propose a bimodal mode of interaction of the protein with RNA. A single mutation in RRM1 changed SRSF1 specificity for RNA and made it active on SMN2 exon7 splicing.

Here the authors identify the sequence bound by Npl3 and solve the structure of the complex using NMR. Npl3 binds directly to the U2 snRNA and melt the stem-loop I, suggesting a chaperoning role during spliceosome active site formation.

Lin28 prevents the processing of pre-let-7 RNAs, but it is not clear where the Lin28 RNA binding domains interact with the RNA. The NMR structure of the Lin28 zinc knuckles with a short RNA motif reveals that each knuckle interacts with an AG dinucleotide, allowing the determination of a consensus motif for pre-let-7 recognition.

NMR-based structural analysis of the RNA duplex formed by SMN2 exon 7 and U1 snRNA reveals that the splicing modifier SMN-C5 pulls the bulged adenine into the RNA helix base stack and transforms the weak 5ʹ splice site of SMN2 exon 7 into a stronger one.

Tra2-β1 is a splicing factor involved in facilitating SMN2 exon 7 splicing. Exon 7 inclusion prevents SMN2 from rescuing the SMN1 deletion, a situation linked to spinal muscular atrophy. The structure of Tra2-β1 in complex with an RNA target is now presented, giving insight into purine recognition by an unusual RNA binding mode.

The RNA-binding ubiquitin E3 ligase TRIM25 plays a critical role in antiviral immunity. Here the authors identify key RNA-binding residues of TRIM25, link RNA binding to antiviral activity, reveal RNA structural and sequence preferences, and investigate binding to the viral genome.

Many organelles in the cell are not encapsulated in a membrane—they are liquid-like domains formed through phase separation. The liquid-like nature of such domains leads to adhesive interactions between the cytoskeleton filaments and organelles.

High-resolution structures of large RNAs and protein–RNA complexes are difficult to solve due to inherent structural flexibility and a high risk of crystallization artefacts. Here, Duss et al. present a novel EPR-based approach to aid structure determination of large RNAs and protein–RNA complexes in solution.

TDP-43 regulates alternative splicing of the cystic fibrosis transmembrane regulator (CFTR) and is found in cytosolic granules associated with several neurodegenerative disorders. A new solution structure of the tandem RNA-recognition motifs (RRMs) that mediate interactions with its UG-rich RNA targets reveals a new RRM arrangement critical for TDP-43 function.

Although UV-induced cross-linking is a widely used method to study RNA-protein complexes, the cross-linking reactions are poorly understood. Here, the authors show that π-stacking interactions between nucleobases and aromatic amino acids play a key role in the cross-linking process.

How heterogeneous nuclear ribonucleoprotein (RNP) F regulates alternative splicing is unclear. Solution structures of three quasi RNA recognition motifs (qRRMs) bound to G-tract RNA now reveal an unusual binding mode, confirmed by mutagenesis and isothermal titration calorimetry analysis. Binding and splicing assays suggest that hnRNP F prevents RNA structure formation.

Ribosomal proteins are transported to the nucleus with the help of importins, from which they are released prior to incorporation into the nascent ribosome. Here the authors report the NMR structure of the ribosomal protein eS26 in complex with the escortin Tsr2 and shed light on the mechanism of eS26 release from importin.

The 3D structure of a diffracting volume can be reconstructed from a set of 2D coherent Bragg diffraction patterns. The overdetermination afforded by ptychography allows the deconvolution of the third dimension, without having to rotate the sample.

Pupylation is a bacterial posttranslational modification pathway with functional analogies to ubiquitination. Here, Özceliket al.report the structures of the Pup Ligase, PafA and the Depupylase, Dop. Mutational analysis revealed residues required for catalysis and for the interaction with Pup.

The authors perform a meta-analysis of cutaneous squamous cell carcinoma, identifying causal variants within skin-specific regulatory elements.

TDP-43 aggregation is observed in amyotrophic lateral sclerosis. Here the authors combine X-ray crystallography, nuclear magnetic resonance and electron microscopy studies and show that physiological oligomerization of TDP-43 is mediated through its N-terminal domain, which forms functional and dynamic oligomers antagonizing pathologic aggregation.

The cellular functions of arrestins are determined in part by the pattern of phosphorylation on the G protein-coupled receptors (GPCRs) to which arrestins bind. Here, authors use a library of synthetic phosphopeptide analogues of the GPCR rhodopsin C-terminus and determine the ability of these peptides to bind and activate arrestins using a variety of biochemical and biophysical methods.

Myotonic dystrophy (DM) type 2 is a neuromuscular pathology caused by large expansions of CCTG repeats. Here the authors find that rbFOX1 RNA binding protein binds to CCUG RNA repeats and competes with MBNL1 for the binding to CCUG repeats, releasing MBNL1 from sequestration in DM2 muscle cells.

Small molecules correcting the splicing deficit of the survival of motor neuron 2 (SMN2) gene have been identified as having therapeutic potential. Here, the authors provide evidence that SMN2 mRNA forms a ribonucleoprotein complex that can be specifically targeted by these small molecules.

Alternative splicing increases genome coding potential and is affected by factors including the hnRNPs. The effect of altering splice site strength on splicing activity is now found to be antagonized by nearby hnRNP H binding sites. Other splicing factor sites may have similar effects and may thus have influenced splice form evolution.