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Deadenylation of mRNAs is generally associated with translational inhibition and mRNA decay. A study now reports that, unexpectedly, highly expressed genes tend to have shorter poly(A) tails and suggests that poly(A) tails can be 'pruned', generating a 30-nucleotide-biased phased distribution, likely due to protection by poly(A)-binding proteins.
The helicase intrinsic to DNA polymerase θ (Polθ), the versatile mediator of microhomology-based repair of DNA double-strand breaks and stalled replication forks, is now revealed to be a member of an elite group of proteins known as annealing helicases. This small family of enzymes remodels DNA intermediates in multiple repair processes that are crucial to preserving genome stability and warding off cancer and aging.
The crystal structure of an oligosaccharyltransferase in complex with a sugar donor and an acceptor peptide provides insight into the mechanism of protein glycosylation and reveals how lipid-linked oligosaccharides are positioned in the enzyme active site.
Assembly of the small ribosomal subunit from an RNA strand and 33 proteins is an intricate and dynamic process. Two cryo-EM studies now provide insight into a complicated complex of at least 51 trans-factors that act on the preribosomal small subunit to sequentially fold it into a 3D molecular machine.
PCSK9 enhances LDL cholesterol (LDL-c) levels by escorting the liver LDL receptor (LDLR) to endosomes and lysosomes for degradation. PCSK9 monoclonal antibodies and RNA-antisense formulations are effective in reducing LDL cholesterol in patients. The recent structural identification of a novel pocket in PCSK9 paves the way to the future development of orally active small-molecule hypocholesterolemic drugs.
The cellular crosstalk between different classes of regulatory noncoding RNAs has reached a new spatial dimension. Jiang et al. reveal an essential role of a nuclear-paraspeckle-organizing long noncoding RNA and its protein partners in regulating the first steps of microRNA biogenesis.
C-type inactivation is a process by which ion flux through a voltage-gated K+ channel is regulated at the selectivity filter. A recent structure of the Kv1.2 channel provides a view into the structural changes of the selectivity filter during C-type inactivation.
PERK is a major sensor of the unfolded protein response controlling cell fate under endoplasmic reticulum (ER) stress. A new study reveals an additional step for optimal PERK signaling, involving the binding of CNPY2 to PERK's luminal domain. The PERK–CNPY2 axis was shown to enhance cell death under ER stress in vivo influence liver disease.
The robustness of the circadian clock deteriorates with aging. Two new studies show that aging reprograms the circadian transcriptome in a cell-type-dependent manner and that such rewiring can be reversed by caloric restriction.
Group II chaperonins facilitate protein folding by undergoing ATP-driven conformational changes. A recent study reveals a tunable allosteric network in group II chaperonins that includes a residue at the intersubunit interface, which is important for assembly and allosteric coordination. The authors also propose that lower cooperativity allows group II chaperonins to achieve optimal substrate folding over a broad range of ATP concentrations.
The monoallelic expression of many imprinted genes in mammals depends on DNA methylation marks that originate from the germ cells. Recent studies in mice and fruit flies evoke a novel, transient mode of genomic imprinting in which oocyte-acquired histone H3 Lys27 trimethylation (H3K27me3) marks are transmitted to the zygote and modulate the allele specificity and timing of gene expression in the early embryo.
Meiotic progression is controlled by cytoplasmic polyadenylation and translational activation of masked, maternal mRNAs. RNA-binding-protein interactions with adjacent cis elements cause local conformational changes to the mRNAs that determine the extent and timing of their activation.
An unusual pairing of homologous X chromosomes occurs during X inactivation. A new study in mouse embryonic stem cells shows that telomeres and the telomeric RNA PAR-TERRA are responsible for additional pairwise interactions that guide Xic–Xic pairing.
Long noncoding (lnc)RNAs are postulated to control diverse biological processes by modulating transcription, yet for most lncRNAs evidence supporting this function has been lacking. A new report describes the role of a novel class of lncRNAs—chromatin-associated enhancer RNAs or cheRNAs—in the regulation of proximal gene expression.
The envelope glycoprotein spike, the sole antigen on the Lassa virus (LASV) surface, constitutes the focal point of the host neutralizing immune response. A high-resolution structure of the trimeric LASV glycoprotein in an antibody-bound form illuminates the molecular architecture of the antigen and reveals the mode of action of the most abundant known class of Lassa-specific human neutralizing antibodies.
Cytoplasmic dyneins transport cellular components from the periphery toward the center of the cell. By moving cargoes along microtubules, dyneins ensure proper cell division, regulate exchange of materials between organelles, and contribute to the internal organization of eukaryotic cells. Two recent studies show that, upon dimerization, cytoplasmic dyneins intrinsically adopt an autoinhibited configuration that can be relieved by other factors to precisely control motor activity and regulate dynein-based transport.
Two new studies show that RNA-binding proteins can mediate distinct and beneficial effects to cells by binding to the extensive double-stranded RNA (dsRNA) structures of inverted-repeat Alu elements (IRAlus). One study reports stress-induced export of the 110-kDa isoform of the adenosine deaminase acting on RNA 1 protein (ADAR1p110) to the cytoplasm, where it binds IRAlus so as to protect many mRNAs encoding anti-apoptotic proteins from degradation. The other study demonstrates that binding of the nuclear helicase DHX9 to IRAlus embedded within RNAs minimizes defects in RNA processing.
Interaction with heterotrimeric G proteins is a hallmark of G-protein-coupled receptor (GPCR) family members, and it is the key step for a diverse range of cell-signaling cascades. A recent cryo-EM structure of the human calcitonin receptor (CTR) in complex with a G-protein heterotrimer reveals novel insights into receptor–G-protein coupling.
