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Naive CD4+ T lymphocytes initially undergo antigen-specific activation to promote a broad-spectrum response before adopting bespoke cytokine expression profiles shaped by intercellular microenvironmental cues, resulting in pathogen-focused modular cytokine responses. Interleukin (IL)-4-induced Gata3 upregulation is important for the helper type 2 T cell (TH2 cell) polarization associated with anti-helminth immunity and misdirected allergic inflammation. Whether additional microenvironmental factors participate is unclear. Using whole mouse-genome CRISPR-Cas9 screens, we discovered a previously unappreciated role for αvß3 integrin in TH2 cell differentiation. Low-level αvß3 expression by naive CD4+ T cells contributed to pan-T cell activation by promoting T-T cell clustering and IL-2/CD25/STAT5 signaling. Subsequently, IL-4/Gata3-induced selective upregulation of αvß3 licensed intercellular αvß3-Thy1 interactions among TH2 cells, enhanced mammalian target of rapamycin (mTOR) signaling, supported differentiation and promoted IL-5/IL-13 production. In mice, αvß3 was required for efficient, allergen-driven, antigen-specific lung TH2 cell responses. Thus, αvß3-expressing TH2 cells form multicellular factories to propagate and amplify TH2 cell responses.
Assuntos
Citocinas , Células Th2 , Camundongos , Animais , Citocinas/metabolismo , Diferenciação Celular , Alérgenos , Pulmão , Mamíferos/metabolismoRESUMO
Recent years have seen revived interest in computer-assisted organic synthesis1,2. The use of reaction- and neural-network algorithms that can plan multistep synthetic pathways have revolutionized this field1,3-7, including examples leading to advanced natural products6,7. Such methods typically operate on full, literature-derived 'substrate(s)-to-product' reaction rules and cannot be easily extended to the analysis of reaction mechanisms. Here we show that computers equipped with a comprehensive knowledge-base of mechanistic steps augmented by physical-organic chemistry rules, as well as quantum mechanical and kinetic calculations, can use a reaction-network approach to analyse the mechanisms of some of the most complex organic transformations: namely, cationic rearrangements. Such rearrangements are a cornerstone of organic chemistry textbooks and entail notable changes in the molecule's carbon skeleton8-12. The algorithm we describe and deploy at https://HopCat.allchemy.net/ generates, within minutes, networks of possible mechanistic steps, traces plausible step sequences and calculates expected product distributions. We validate this algorithm by three sets of experiments whose analysis would probably prove challenging even to highly trained chemists: (1) predicting the outcomes of tail-to-head terpene (THT) cyclizations in which substantially different outcomes are encoded in modular precursors differing in minute structural details; (2) comparing the outcome of THT cyclizations in solution or in a supramolecular capsule; and (3) analysing complex reaction mixtures. Our results support a vision in which computers no longer just manipulate known reaction types1-7 but will help rationalize and discover new, mechanistically complex transformations.
Assuntos
Algoritmos , Técnicas de Química Sintética , Ciclização , Redes Neurais de Computação , Terpenos , Cátions/química , Bases de Conhecimento , Terpenos/química , Técnicas de Química Sintética/métodos , Produtos Biológicos/síntese química , Produtos Biológicos/química , Reprodutibilidade dos Testes , SoluçõesRESUMO
The activating receptor CD226 is expressed on lymphocytes, monocytes, and platelets and promotes anti-tumor immunity in pre-clinical models. Here, we examined the role of CD226 in the function of tumor-infiltrating lymphocytes (TILs) and resistance to immunotherapy. In murine tumors, a large proportion of CD8+ TILs had decreased surface expression of CD226 and exhibited features of dysfunction, whereas CD226hi TILs were highly functional. This correlation was seen also in TILs isolated from HNSCC patients. Mutation of CD226 at tyrosine 319 (Y319) led to increased CD226 surface expression, enhanced anti-tumor immunity and improved efficacy of immune checkpoint blockade (ICB). Mechanistically, tumor-derived CD155, the ligand for CD226, initiated phosphorylation of Y319 by Src kinases, thereby enabling ubiquitination of CD226 by CBL-B, internalization, and proteasomal degradation. In pre-treatment samples from melanoma patients, CD226+CD8+ T cells correlated with improved progression-free survival following ICB. Our findings argue for the development of therapies aimed at maintaining the expression of CD226.
Assuntos
Antígenos de Diferenciação de Linfócitos T/imunologia , Linfócitos T CD8-Positivos/imunologia , Receptores Virais/imunologia , Animais , Linhagem Celular , Linhagem Celular Tumoral , Células HEK293 , Humanos , Inibidores de Checkpoint Imunológico/imunologia , Imunoterapia/métodos , Células Jurkat , Linfócitos do Interstício Tumoral/imunologia , Masculino , Melanoma/imunologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
The control of tetrahedral carbon stereocentres remains a focus of modern synthetic chemistry and is enabled by their configurational stability. By contrast, trisubstituted nitrogen1, phosphorus2 and sulfur compounds3 undergo pyramidal inversion, a fundamental and well-recognized stereochemical phenomenon that is widely exploited4. However, the stereochemistry of oxonium ions-compounds bearing three substituents on a positively charged oxygen atom-is poorly developed and there are few applications of oxonium ions in synthesis beyond their existence as reactive intermediates5,6. There are no examples of configurationally stable oxonium ions in which the oxygen atom is the sole stereogenic centre, probably owing to the low barrier to oxygen pyramidal inversion7 and the perception that all oxonium ions are highly reactive. Here we describe the design, synthesis and characterization of a helically chiral triaryloxonium ion in which inversion of the oxygen lone pair is prevented through geometric restriction to enable it to function as a determinant of configuration. A combined synthesis and quantum calculation approach delineates design principles that enable configurationally stable and room-temperature isolable salts to be generated. We show that the barrier to inversion is greater than 110 kJ mol-1 and outline processes for resolution. This constitutes, to our knowledge, the only example of a chiral non-racemic and configurationally stable molecule in which the oxygen atom is the sole stereogenic centre.
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The origin of vertebrate paired appendages is one of the most investigated and debated examples of evolutionary novelty1-7. Paired appendages are widely considered as key innovations that enabled new opportunities for controlled swimming and gill ventilation and were prerequisites for the eventual transition from water to land. The past 150 years of debate8-10 has been shaped by two contentious theories4,5: the ventrolateral fin-fold hypothesis9,10 and the archipterygium hypothesis8. The latter proposes that fins and girdles evolved from an ancestral gill arch. Although studies in animal development have revived interest in this idea11-13, it is apparently unsupported by fossil evidence. Here we present palaeontological support for a pharyngeal basis for the vertebrate shoulder girdle. We use computed tomography scanning to reveal details of the braincase of Kolymaspis sibirica14, an Early Devonian placoderm fish from Siberia, that suggests a pharyngeal component of the shoulder. We combine these findings with refreshed comparative anatomy of placoderms and jawless outgroups to place the origin of the shoulder girdle on the sixth branchial arch. These findings provide a novel framework for understanding the origin of the pectoral girdle. Our evidence clarifies the location of the presumptive head-trunk interface in jawless fishes and explains the constraint on branchial arch number in gnathostomes15. The results revive a key aspect of the archipterygium hypothesis and help reconcile it with the ventrolateral fin-fold model.
Assuntos
Nadadeiras de Animais , Evolução Biológica , Peixes , Fósseis , Vertebrados , Animais , Nadadeiras de Animais/anatomia & histologia , Peixes/anatomia & histologia , Paleontologia , Tomografia Computadorizada por Raios X , Vertebrados/anatomia & histologia , SibériaRESUMO
Dinosaurs and pterosaurs have remarkable diversity and disparity through most of the Mesozoic Era1-3. Soon after their origins, these reptiles diversified into a number of long-lived lineages, evolved unprecedented ecologies (for example, flying, large herbivorous forms) and spread across Pangaea4,5. Recent discoveries of dinosaur and pterosaur precursors6-10 demonstrated that these animals were also speciose and widespread, but those precursors have few if any well-preserved skulls, hands and associated skeletons11,12. Here we present a well-preserved partial skeleton (Upper Triassic, Brazil) of the new lagerpetid Venetoraptor gassenae gen. et sp. nov. that offers a more comprehensive look into the skull and ecology of one of these precursors. Its skull has a sharp, raptorial-like beak, preceding that of dinosaurs by around 80 million years, and a large hand with long, trenchant claws that firmly establishes the loss of obligatory quadrupedalism in these precursor lineages. Combining anatomical information of the new species with other dinosaur and pterosaur precursors shows that morphological disparity of precursors resembles that of Triassic pterosaurs and exceeds that of Triassic dinosaurs. Thus, the 'success' of pterosaurs and dinosaurs was a result of differential survival among a broader pool of ecomorphological variation. Our results show that the morphological diversity of ornithodirans started to flourish among early-diverging lineages and not only after the origins of dinosaurs and pterosaurs.
Assuntos
Dinossauros , Filogenia , Répteis , Animais , Bico/anatomia & histologia , Dinossauros/anatomia & histologia , Dinossauros/classificação , Répteis/anatomia & histologia , Répteis/classificação , Crânio/anatomia & histologia , Fósseis , EsqueletoRESUMO
Decades of previous efforts to develop renal-sparing polyene antifungals were misguided by the classic membrane permeabilization model1. Recently, the clinically vital but also highly renal-toxic small-molecule natural product amphotericin B was instead found to kill fungi primarily by forming extramembraneous sponge-like aggregates that extract ergosterol from lipid bilayers2-6. Here we show that rapid and selective extraction of fungal ergosterol can yield potent and renal-sparing polyene antifungals. Cholesterol extraction was found to drive the toxicity of amphotericin B to human renal cells. Our examination of high-resolution structures of amphotericin B sponges in sterol-free and sterol-bound states guided us to a promising structural derivative that does not bind cholesterol and is thus renal sparing. This derivative was also less potent because it extracts ergosterol more slowly. Selective acceleration of ergosterol extraction with a second structural modification yielded a new polyene, AM-2-19, that is renal sparing in mice and primary human renal cells, potent against hundreds of pathogenic fungal strains, resistance evasive following serial passage in vitro and highly efficacious in animal models of invasive fungal infections. Thus, rational tuning of the dynamics of interactions between small molecules may lead to better treatments for fungal infections that still kill millions of people annually7,8 and potentially other resistance-evasive antimicrobials, including those that have recently been shown to operate through supramolecular structures that target specific lipids9.
Assuntos
Antifúngicos , Rim , Polienos , Esteróis , Animais , Humanos , Camundongos , Anfotericina B/análogos & derivados , Anfotericina B/química , Anfotericina B/toxicidade , Antifúngicos/química , Antifúngicos/metabolismo , Antifúngicos/farmacologia , Antifúngicos/toxicidade , Células Cultivadas , Colesterol/química , Colesterol/metabolismo , Farmacorresistência Fúngica , Ergosterol/química , Ergosterol/metabolismo , Rim/efeitos dos fármacos , Cinética , Testes de Sensibilidade Microbiana , Micoses/tratamento farmacológico , Micoses/microbiologia , Polienos/química , Polienos/metabolismo , Polienos/farmacologia , Inoculações Seriadas , Esteróis/química , Esteróis/metabolismo , Fatores de TempoRESUMO
Lung cancer is the leading cause of cancer-associated mortality worldwide1. Here we analysed 1,644 tumour regions sampled at surgery or during follow-up from the first 421 patients with non-small cell lung cancer prospectively enrolled into the TRACERx study. This project aims to decipher lung cancer evolution and address the primary study endpoint: determining the relationship between intratumour heterogeneity and clinical outcome. In lung adenocarcinoma, mutations in 22 out of 40 common cancer genes were under significant subclonal selection, including classical tumour initiators such as TP53 and KRAS. We defined evolutionary dependencies between drivers, mutational processes and whole genome doubling (WGD) events. Despite patients having a history of smoking, 8% of lung adenocarcinomas lacked evidence of tobacco-induced mutagenesis. These tumours also had similar detection rates for EGFR mutations and for RET, ROS1, ALK and MET oncogenic isoforms compared with tumours in never-smokers, which suggests that they have a similar aetiology and pathogenesis. Large subclonal expansions were associated with positive subclonal selection. Patients with tumours harbouring recent subclonal expansions, on the terminus of a phylogenetic branch, had significantly shorter disease-free survival. Subclonal WGD was detected in 19% of tumours, and 10% of tumours harboured multiple subclonal WGDs in parallel. Subclonal, but not truncal, WGD was associated with shorter disease-free survival. Copy number heterogeneity was associated with extrathoracic relapse within 1 year after surgery. These data demonstrate the importance of clonal expansion, WGD and copy number instability in determining the timing and patterns of relapse in non-small cell lung cancer and provide a comprehensive clinical cancer evolutionary data resource.
Assuntos
Carcinoma Pulmonar de Células não Pequenas , Neoplasias Pulmonares , Humanos , Adenocarcinoma de Pulmão/etiologia , Adenocarcinoma de Pulmão/genética , Adenocarcinoma de Pulmão/patologia , Carcinoma Pulmonar de Células não Pequenas/etiologia , Carcinoma Pulmonar de Células não Pequenas/genética , Carcinoma Pulmonar de Células não Pequenas/patologia , Neoplasias Pulmonares/etiologia , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patologia , Mutação , Recidiva Local de Neoplasia/genética , Filogenia , Resultado do Tratamento , Fumar/genética , Fumar/fisiopatologia , Mutagênese , Variações do Número de Cópias de DNARESUMO
Reservoirs of dense atomic gas (primarily hydrogen) contain approximately 90 per cent of the neutral gas at a redshift of 3, and contribute to between 2 and 3 per cent of the total baryons in the Universe1-4. These 'damped Lyman α systems'-so called because they absorb Lyman α photons within and from background sources-have been studied for decades, but only through absorption lines present in the spectra of background quasars and γ-ray bursts5-10. Such pencil beams do not constrain the physical extent of the systems. Here we report integral-field spectroscopy of a bright, gravitationally lensed galaxy at a redshift of 2.7 with two foreground damped Lyman α systems. These systems are greater than 238 kiloparsecs squared in extent, with column densities of neutral hydrogen varying by more than an order of magnitude on scales of less than 3 kiloparsecs. The mean column densities are between 1020.46 and 1020.84 centimetres squared and the total masses are greater than 5.5 × 108-1.4 × 109 times the mass of the Sun, showing that they contain the necessary fuel for the next generation of star formation, consistent with relatively massive, low-luminosity primeval galaxies at redshifts greater than 2.
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Fully automated synthetic chemistry would substantially change the field by providing broad on-demand access to small molecules. However, the reactions that can be run autonomously are still limited. Automating the stereospecific assembly of Csp3-C bonds would expand access to many important types of functional organic molecules1. Previously, methyliminodiacetic acid (MIDA) boronates were used to orchestrate the formation of Csp2-Csp2 bonds and were effective building blocks for automating the synthesis of many small molecules2, but they are incompatible with stereospecific Csp3-Csp2 and Csp3-Csp3 bond-forming reactions3-10. Here we report that hyperconjugative and steric tuning provide a new class of tetramethyl N-methyliminodiacetic acid (TIDA) boronates that are stable to these conditions. Charge density analysis11-13 revealed that redistribution of electron density increases covalency of the N-B bond and thereby attenuates its hydrolysis. Complementary steric shielding of carbonyl π-faces decreases reactivity towards nucleophilic reagents. The unique features of the iminodiacetic acid cage2, which are essential for generalized automated synthesis, are retained by TIDA boronates. This enabled Csp3 boronate building blocks to be assembled using automated synthesis, including the preparation of natural products through automated stereospecific Csp3-Csp2 and Csp3-Csp3 bond formation. These findings will enable increasingly complex Csp3-rich small molecules to be accessed via automated assembly.
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The discovery of antibiotics more than 80 years ago has led to considerable improvements in human and animal health. Although antibiotic resistance in environmental bacteria is ancient, resistance in human pathogens is thought to be a modern phenomenon that is driven by the clinical use of antibiotics1. Here we show that particular lineages of methicillin-resistant Staphylococcus aureus-a notorious human pathogen-appeared in European hedgehogs in the pre-antibiotic era. Subsequently, these lineages spread within the local hedgehog populations and between hedgehogs and secondary hosts, including livestock and humans. We also demonstrate that the hedgehog dermatophyte Trichophyton erinacei produces two ß-lactam antibiotics that provide a natural selective environment in which methicillin-resistant S. aureus isolates have an advantage over susceptible isolates. Together, these results suggest that methicillin resistance emerged in the pre-antibiotic era as a co-evolutionary adaptation of S. aureus to the colonization of dermatophyte-infected hedgehogs. The evolution of clinically relevant antibiotic-resistance genes in wild animals and the connectivity of natural, agricultural and human ecosystems demonstrate that the use of a One Health approach is critical for our understanding and management of antibiotic resistance, which is one of the biggest threats to global health, food security and development.
Assuntos
Antibacterianos/história , Arthrodermataceae/metabolismo , Ouriços/metabolismo , Ouriços/microbiologia , Resistência a Meticilina/genética , Staphylococcus aureus Resistente à Meticilina/genética , Seleção Genética/genética , Animais , Antibacterianos/metabolismo , Arthrodermataceae/genética , Dinamarca , Europa (Continente) , Evolução Molecular , Mapeamento Geográfico , História do Século XX , Humanos , Staphylococcus aureus Resistente à Meticilina/metabolismo , Nova Zelândia , Saúde Única , Penicilinas/biossíntese , Filogenia , beta-Lactamas/metabolismoRESUMO
The local regulation of type 2 immunity relies on dialog between the epithelium and the innate and adaptive immune cells. Here we found that alarmin-induced expression of the co-stimulatory molecule OX40L on group 2 innate lymphoid cells (ILC2s) provided tissue-restricted T cell co-stimulation that was indispensable for Th2 and regulatory T (Treg) cell responses in the lung and adipose tissue. Interleukin (IL)-33 administration resulted in organ-specific surface expression of OX40L on ILC2s and the concomitant expansion of Th2 and Treg cells, which was abolished upon deletion of OX40L on ILC2s (Il7raCre/+Tnfsf4fl/fl mice). Moreover, Il7raCre/+Tnfsf4fl/fl mice failed to mount effective Th2 and Treg cell responses and corresponding adaptive type 2 pulmonary inflammation arising from Nippostrongylus brasiliensis infection or allergen exposure. Thus, the increased expression of OX40L in response to IL-33 acts as a licensing signal in the orchestration of tissue-specific adaptive type 2 immunity, without which this response fails to establish.
Assuntos
Imunidade Adaptativa/imunologia , Imunidade Inata/imunologia , Glicoproteínas de Membrana/imunologia , Linfócitos T Reguladores/imunologia , Células Th2/imunologia , Fatores de Necrose Tumoral/imunologia , Animais , Diferenciação Celular/imunologia , Interleucina-33/imunologia , Ativação Linfocitária/imunologia , Linfócitos/imunologia , Camundongos , Ligante OX40RESUMO
The conceptual origins of ribosome specialization can be traced back to the earliest days of molecular biology. Yet, this field has only recently begun to gather momentum, with numerous studies identifying distinct heterogeneous ribosome populations across multiple species and model systems. It is proposed that some of these compositionally distinct ribosomes may be functionally specialized and able to regulate the translation of specific mRNAs. Identification and functional characterization of specialized ribosomes has the potential to elucidate a novel layer of gene expression control, at the level of translation, where the ribosome itself is a key regulatory player. In this review, we discuss different sources of ribosome heterogeneity, evidence for ribosome specialization, and also the future directions of this exciting field.
Assuntos
Biossíntese de Proteínas , Proteínas Ribossômicas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Ribossômico/metabolismo , Proteínas Ribossômicas/metabolismo , Ribossomos/genética , Ribossomos/metabolismoRESUMO
RhoA plays a crucial role in neuronal polarization, where its action restraining axon outgrowth has been thoroughly studied. We now report that RhoA has not only an inhibitory but also a stimulatory effect on axon development depending on when and where exerts its action and the downstream effectors involved. In cultured hippocampal neurons, FRET imaging revealed that RhoA activity selectively localized in growth cones of undifferentiated neurites, whereas in developing axons it displayed a biphasic pattern, being low in nascent axons and high in elongating ones. RhoA-Rho kinase (ROCK) signaling prevented axon initiation but had no effect on elongation, whereas formin inhibition reduced axon extension without significantly altering initial outgrowth. In addition, RhoA-mDia signaling promoted axon elongation by stimulating growth cone microtubule stability and assembly, as opposed to RhoA-ROCK signaling, which restrained growth cone microtubule assembly and protrusion.
Assuntos
Axônios , Cones de Crescimento , Microtúbulos , Transdução de Sinais , Proteína rhoA de Ligação ao GTP , Microtúbulos/metabolismo , Animais , Proteína rhoA de Ligação ao GTP/metabolismo , Axônios/metabolismo , Cones de Crescimento/metabolismo , Quinases Associadas a rho/metabolismo , Hipocampo/metabolismo , Hipocampo/citologia , Ratos , Forminas/metabolismo , Células Cultivadas , Neurônios/metabolismoRESUMO
BACKGROUND: Divarasib (GDC-6036) is a covalent KRAS G12C inhibitor that was designed to have high potency and selectivity. METHODS: In a phase 1 study, we evaluated divarasib administered orally once daily (at doses ranging from 50 to 400 mg) in patients who had advanced or metastatic solid tumors that harbor a KRAS G12C mutation. The primary objective was an assessment of safety; pharmacokinetics, investigator-evaluated antitumor activity, and biomarkers of response and resistance were also assessed. RESULTS: A total of 137 patients (60 with non-small-cell lung cancer [NSCLC], 55 with colorectal cancer, and 22 with other solid tumors) received divarasib. No dose-limiting toxic effects or treatment-related deaths were reported. Treatment-related adverse events occurred in 127 patients (93%); grade 3 events occurred in 15 patients (11%) and a grade 4 event in 1 patient (1%). Treatment-related adverse events resulted in a dose reduction in 19 patients (14%) and discontinuation of treatment in 4 patients (3%). Among patients with NSCLC, a confirmed response was observed in 53.4% of patients (95% confidence interval [CI], 39.9 to 66.7), and the median progression-free survival was 13.1 months (95% CI, 8.8 to could not be estimated). Among patients with colorectal cancer, a confirmed response was observed in 29.1% of patients (95% CI, 17.6 to 42.9), and the median progression-free survival was 5.6 months (95% CI, 4.1 to 8.2). Responses were also observed in patients with other solid tumors. Serial assessment of circulating tumor DNA showed declines in KRAS G12C variant allele frequency associated with response and identified genomic alterations that may confer resistance to divarasib. CONCLUSIONS: Treatment with divarasib resulted in durable clinical responses across KRAS G12C-positive tumors, with mostly low-grade adverse events. (Funded by Genentech; ClinicalTrials.gov number, NCT04449874.).
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Antineoplásicos , Carcinoma Pulmonar de Células não Pequenas , Neoplasias Colorretais , Inibidores Enzimáticos , Neoplasias Pulmonares , Humanos , Antineoplásicos/administração & dosagem , Antineoplásicos/efeitos adversos , Antineoplásicos/uso terapêutico , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/genética , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/genética , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/genética , Mutação , Proteínas Proto-Oncogênicas p21(ras)/genética , Administração Oral , Inibidores Enzimáticos/administração & dosagem , Inibidores Enzimáticos/efeitos adversos , Inibidores Enzimáticos/uso terapêuticoRESUMO
Besides regulating splicing, the conserved spliceosome component SmD1 (Small nuclear ribonucleoprotein D1)b promotes posttranscriptional silencing of sense transgenes (S-PTGS [post-transcriptional genesilencing]). Here, we show that the conserved spliceosome component PRP39 (Pre-mRNA-processing factor 39)a also plays a role in S-PTGS in Arabidopsis thaliana. However, PRP39a and SmD1b actions appear distinct in both splicing and S-PTGS. Indeed, RNAseq-based analysis of expression level and alternative splicing in prp39a and smd1b mutants identified different sets of deregulated transcripts and noncoding RNAs. Moreover, double mutant analyses involving prp39a or smd1b and RNA quality control (RQC) mutants revealed distinct genetic interactions for SmD1b and PRP39a with nuclear RQC machineries, suggesting nonredundant roles in the RQC/PTGS interplay. Supporting this hypothesis, a prp39a smd1b double mutant exhibited enhanced suppression of S-PTGS compared to the single mutants. Because the prp39a and smd1b mutants (i) showed no major changes in the expression of PTGS or RQC components or in small RNA production and (ii) do not alter PTGS triggered by inverted-repeat transgenes directly producing dsRNA (IR-PTGS), PRP39a, and SmD1b appear to synergistically promote a step specific to S-PTGS. We propose that, independently from their specific roles in splicing, PRP39a and SmD1b limit 3'-to-5' and/or 5'-to-3' degradation of transgene-derived aberrant RNAs in the nucleus, thus favoring the export of aberrant RNAs to the cytoplasm where their conversion into double-stranded RNA (dsRNA) initiates S-PTGS.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Spliceossomos/genética , Spliceossomos/metabolismo , Transgenes , RNA Interferente Pequeno/genética , RNA de Cadeia Dupla/genética , RNA de Cadeia Dupla/metabolismo , Interferência de RNARESUMO
The natural product hinokitiol mobilizes iron across lipid bilayers at low concentrations and restores hemoglobinization in iron transporter protein-deficient systems. But hinokitiol fails to similarly mobilize iron at higher concentrations, limiting its uses in chemical biology and medicine. Here we show that at higher concentrations, hinokitiol3:Fe(III) complexes form large, higher-order aggregates, leading to loss of transmembrane iron mobilization. Guided by this understanding and systematic structure-function studies enabled by modular synthesis, we identified FeM-1269, which minimally aggregates and dose-dependently mobilizes iron across lipid bilayers even at very high concentrations. In contrast to hinokitiol, FeM-1269 is also well-tolerated in animals at high doses for extended periods of time. In a mouse model of anemia of inflammation, FeM-1269 increases serum iron, transferrin saturation, hemoglobin and hematocrit. This rationally developed iron-mobilizing small molecule has enhanced potential as a molecular prosthetic for understanding and potentially treating iron transporter deficiencies.
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Stellar mergers are a brief but common phase in the evolution of binary star systems1,2. These events have many astrophysical implications; for example, they may lead to the creation of atypical stars (such as magnetic stars3, blue stragglers4 and rapid rotators5), they play an important part in our interpretation of stellar populations6 and they represent formation channels of compact-object mergers7. Although a handful of stellar mergers have been observed directly8,9, the central remnants of these events were shrouded by an opaque shell of dust and molecules10, making it impossible to observe their final state (for example, as a single merged star or a tighter, surviving binary11). Here we report observations of an unusual, ring-shaped ultraviolet ('blue') nebula and the star at its centre, TYC 2597-735-1. The nebula has two opposing fronts, suggesting a bipolar outflow of material from TYC 2597-735-1. The spectrum of TYC 2597-735-1 and its proximity to the Galactic plane suggest that it is an old star, yet it has abnormally low surface gravity and a detectable long-term luminosity decay, which is uncharacteristic for its evolutionary stage. TYC 2597-735-1 also exhibits Hα emission, radial-velocity variations, enhanced ultraviolet radiation and excess infrared emission-signatures of dusty circumstellar disks12, stellar activity13 and accretion14. Combined with stellar evolution models, the observations suggest that TYC 2597-735-1 merged with a lower-mass companion several thousand years ago. TYC 2597-735-1 provides a look at an unobstructed stellar merger at an evolutionary stage between its dynamic onset and the theorized final equilibrium state, enabling the direct study of the merging process.
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Pterosaurs were the first vertebrates to evolve powered flight1 and comprised one of the main evolutionary radiations in terrestrial ecosystems of the Mesozoic era (approximately 252-66 million years ago), but their origin has remained an unresolved enigma in palaeontology since the nineteenth century2-4. These flying reptiles have been hypothesized to be the close relatives of a wide variety of reptilian clades, including dinosaur relatives2-8, and there is still a major morphological gap between those forms and the oldest, unambiguous pterosaurs from the Upper Triassic series. Here, using recent discoveries of well-preserved cranial remains, microcomputed tomography scans of fragile skull bones (jaws, skull roofs and braincases) and reliably associated postcrania, we demonstrate that lagerpetids-a group of cursorial, non-volant dinosaur precursors-are the sister group of pterosaurs, sharing numerous synapomorphies across the entire skeleton. This finding substantially shortens the temporal and morphological gap between the oldest pterosaurs and their closest relatives and simultaneously strengthens the evidence that pterosaurs belong to the avian line of archosaurs. Neuroanatomical features related to the enhanced sensory abilities of pterosaurs9 are already present in lagerpetids, which indicates that these features evolved before flight. Our evidence illuminates the first steps of the assembly of the pterosaur body plan, whose conquest of aerial space represents a remarkable morphofunctional innovation in vertebrate evolution.
Assuntos
Osso e Ossos/anatomia & histologia , Dinossauros/anatomia & histologia , Dinossauros/classificação , Fósseis , Filogenia , Animais , Calibragem , Crânio/anatomia & histologia , Fatores de Tempo , Asas de Animais/anatomia & histologia , Microtomografia por Raio-XRESUMO
This article reflects on sustainability in the context of scientific conferences with emphasis on environmental, diversity, inclusivity, and intellectual aspects. We argue that it is imperative to embrace sustainability as a broad concept during conference organization. In-person conferences have an obvious environmental impact but mitigating strategies can be implemented, such as incentivizing low-emission travel, offering fellowships to support sustainable traveling, and promoting use of public transport or car-pooling. Utilizing eco-conscious venues, catering, and accommodations, along with minimizing resource wastage, further reduces environmental impact. Additional considerations include facilitating hybrid format conferences that allow both in-person and online attendance. Hybrid conferences enhance global participation whilst reducing resource consumption and environmental impact. Often-overlooked benefits can arise from the simple recording of talks to enable asynchronous viewing for people unable to attend in person, in addition to providing a legacy of knowledge that, for example, could support the training of early career researchers (ECRs) or newcomers in the field. The longevity of a research field, intellectual sustainability, requires an inclusive conference atmosphere, offering optimal opportunities for ECRs, minority groups, and researchers from emerging countries. Diversity and inclusivity not only enrich conference experiences but also enhances creativity and innovation.