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A newly engineered phosphoserine synthetase/tRNA pair allows quantitative insertion of phosphoserine or, when coupled with metabolic rewiring, a non-hydrolyzable analog into protein sequences, leading to high yields of modified constructs for functional analysis.

A new approach to evolve novel aminoacyl-tRNA synthetase–tRNA pairs with orthogonal substrate specificity is applied to generate a system to site-specifically incorporate phosphothreonine into proteins, enabling functional studies of this post-translational modification.

Non-canonical amino acids (ncAAs) can be incorporated into proteins in cells using orthogonal aminaocyl–tRNA synthetase/tRNA pairs; the most widely adopted system is based on a pyrrolysyl–tRNA synthetase (PylRS)/tRNA pair. Now, three new PylRS/tRNA pairs have been developed that are mutually orthogonal and can be used together to site-specifically incorporate three distinct ncAAs into a single protein.

Mutually orthogonal aminoacyl transfer RNA synthetase/transfer RNA pairs are required for genetically encoding non-canonical amino acids into proteins, as well as for the encoded cellular synthesis of polymers and macrocycles; however, the scalable discovery of such pairs is challenging. A quintuply orthogonal set of pyrrolysyl-tRNA synthetase/pyrrolysyl-tRNA pairs has now been generated through tRNA screening, engineering and directed evolution.

Macrocyclic peptides can be genetically encoded and synthesized in cells; however, the programmable diversity is limited. Now, macrocycles containing two non-canonical amino acids have been genetically encoded and synthesized in codon-reassigned Syn61Δ3 cells. Incorporating diverse hydroxy acids in Syn61Δ3 cells enables the synthesis of non-natural depsipeptides containing either one or two ester bonds.

Non-standard amino acids are incorporated into proteins at large numbers of sites using evolved translation components in recoded bacteria.

Non-canonical amino acids can be incorporated into proteins through translation of orthogonal mRNAs. Now, automating the design of orthogonal mRNAs—which are more selectively and efficiently translated—in combination with compact orthogonal aminoacyl-tRNA synthetase/tRNA expression systems, enables the incorporation of four distinct non-canonical monomers via a 68-codon genetic code.

A method combining genetic-code expansion, bioorthogonal Staudinger reduction and sortase-mediated transpeptidation enables site-specific and orthogonal modification of proteins with ubiquitin and SUMO in vitro and in living cells.

A series of quadruplet decoding tRNAs has been developed to form an optimized orthogonal translation system. These tRNAs enable efficient, site-specific incorporation of multiple unnatural amino acids into a protein, with a substantial increase in yield over previous methods. The amino acids are then used to site-specifically label a protein with a pair of fluorophores, enabling studies of the protein's dynamics.

The ability to reprogramme cellular translation and genomes to produce non-canonical biopolymers has wide-ranging applications, including in therapeutics, but has yet to be fully realized. In this Review, de la Torre and Chin discuss recent advances towards achieving this goal.

Spondyloarthropathies are characterized by a distinct pattern of inflammation at distinct anatomical sites and are associated with elevated expression of interleukin 23 (IL-23). Daniel Cua and his colleagues identify an IL-23–responsive CD4⁻CD8⁻ T cell population located within entheses. Systemic overexpression of IL-23 activates these cells and recapitulates aspects of the human disease in mice, and neutralization of IL-17 and IL-22 decreases pathology, suggesting new therapeutic targets for these disorders.

New strategies are needed to address treatment resistance in glioblastoma. Here the authors show that TP53-mutant glioblastomas rely upon ATM-dependent double strand break repair to resist DNA-damaging therapy, rendering them vulnerable to drug combinations employing ATM inhibitors.

Ochre, a strain of Escherichia coli engineered to have a single stop codon, enables reassignment of four codons for non-degenerate functions, such as incorporation of non-standard amino acids into proteins.

tRNA display enables the direct selection of orthogonal aminoacyl-tRNA synthetases that acylate orthogonal tRNAs with non-canonical monomers, enabling in vivo synthesis of proteins that include these monomers and expanding the repertoire of the genetic code.

Whether interleukin 23 (IL-23) affects the differentiation of or simply the maintenance of IL-17–producing helper T cells (T_H-17 cells) is unclear. Cua and colleagues show that IL-23 is required for the full differentiation and proliferation of effector T_H-17 cells in vivo.

The absence of scaffold protein Ambra1 leads to hyperproliferation and growth in mouse models. Here the authors show that Ambra1 deficiency accelerates melanoma growth and increases metastasis in mouse models of melanoma through FAK1 hyperactivation.

Essential enzymes in genetically modified organisms are computationally redesigned to functionally depend on non-standard amino acids, thereby achieving biocontainment with unprecedented resistance to escape by evolution or by supplementation with environmental metabolites.

Lysine acetylation regulates the function of soluble proteins in vivo, yet it remains largely unexplored whether lysine acetylation regulates the function of membrane proteins. Here, the authors map lysine acetylation predominantly in membrane-interaction regions in peripheral membrane proteins and show with three candidate proteins how lysine acetylation is a regulator of membrane protein function.

Rational design of live-attenuated RNA viruses with potential as vaccines is enabled by identification of sequence rules for zinc finger antiviral protein.

Developing inhibitors that target specific protein-protein interactions (PPIs) is challenging. Here, the authors show that target selectivity and PPI blocking can be achieved simultaneously with PPI inhibitors that contain two functional modules, and create a paralog-selective PSD-95 inhibitor as proof-of-concept.

The discovery of IL-17-producing T cells has revolutionized our understanding of autoimmune diseases. However, much of the IL-17 released during an immune response is produced before T cells can be activated. Here, Daniel Cua and Cristina Tato describe the cellular sources, transcriptional regulation and physiological relevance of this early IL-17 production.

Engineered variants of cysteine dioxygenase containing a halogen-substituted tyrosine analog provide insights into the process of Cys–Tyr cross-link formation and indicate that the enzyme can catalyze oxidative cleavage of a carbon–fluorine bond.

In-depth analyses of protein expression studies are used to derive a new codon-influence metric that correlates with global protein levels, mRNA levels and mRNA lifetimes in vivo, indicating tight coupling between translation efficiency and mRNA stability; genes redesigned based on these analyses consistently yield high protein expression levels both in vivo and in vitro.

T cells are intrinsically more malleable than previously thought. Two studies now show that existing T helper type 2 cells can be converted into alternative CD4⁺ T helper cells that coexpress interleukins 9 and 10.

A previously unknown function for T_H17 cell–derived IL-26 as a direct antimicrobial agent and activator of DNA-sensing innate immunity is now reported.

Myosin and actin are known to reshape the plasma membrane during endocytosis. Myosin 1b regulates the actin-dependent formation of tubules at the trans-Golgi network. As such, it has a critical role in initiating post-Golgi carrier formation.

RNA nanotechnology is utilized for directional control by altering the orientation of arrow-shaped RNAs for either ligand-display on extracellular vesicle or to regulate intracellular trafficking of siRNA or miRNA in cancer treatment.

Cua and colleagues discuss the cellular and molecular rationale for targeting IL-12 and IL-23 for therapeutic purposes in inflammatory diseases; they also review existing clinical data, discuss potential side effects, and propose future directions for targeting these cytokines in additional disorders.

The electronic structure of copper-based metalloproteins is important for their function in biological processes, but studying this from a computational standpoint can be challenging. Here, the authors report a dynamical mean field theory approach which reveals the role of strong electronic correlation effects in oxygen binding in the hemocyanin protein.

T helper cells that produce interleukin 17 can promote a range of immune-mediated inflammatory diseases. Papers in Nature and Immunity suggest transforming growth factor-β promotes the differentiation of these pathogenic cells.

Macrophages and dendritic cells contribute to gut homeostasis and mucosal immune defense. Here, Aychek et al. describe an IL-23-based crosstalk between these cells that prevents lethal immunopathology during Citrobacter rodentiuminfection.

Inflammatory cells invade the brain after stroke, but their role in disease has been unclear. Now, Akihiko Yoshimura and colleagues report that a particular population of T cells that express the inflammatory cytokine IL-17 plays a key role in stroke progression: depletion of these cells—even as late as 1 day after stroke—can alleviate brain injury in mice pages 844–846).

Negative selection of double-positive thymocytes that express autoreactive T-cell receptors plays a crucial role in the maintenance of self-tolerance. Here, the authors provide evidence that the cytokine IL-23 produced by thymic dendritic cells is involved in the depletion of double-positive thymocytes.

T helper 17 (T_H17) cells promote protective immune responses against infection, particularly at barrier sites, but they can also have pathogenic roles in inflammatory diseases. In this Review, the authors describe the factors that control the development and maintenance of T_H17 cells, and discuss their diverse functions in both health and disease.

The heterodimeric cytokine IL-27 consists of the subunits p28 and EBI3. Hunter and colleagues demonstrate that p28 acting alone can inhibit the signaling of many cytokines by interfering with the common receptor gp130.

The transcription factor RORγt is expressed in many cell types. Eberl and colleagues show that intestinal homeostasis is regulated by an IL-25-dependent feedback pathway involving IL-22-expressing RORγt⁺ innate lymphoid cells.

Quantum gas microscopes provide high-resolution real-space snapshots of quantum many-body systems. Now machine-learning techniques are used in choosing theoretical descriptions according to the consistency of their predictions with these snapshots.