RESUMEN
Neutrophils are sentinel immune cells with essential roles for antimicrobial defense. Most of our knowledge on neutrophil tissue navigation derived from wounding and infection models, whereas allergic conditions remained largely neglected. Here, we analyzed allergen-challenged mouse tissues and discovered that degranulating mast cells (MCs) trap living neutrophils inside them. MCs release the attractant leukotriene B4 to re-route neutrophils toward them, thus exploiting a chemotactic system that neutrophils normally use for intercellular communication. After MC intracellular trap (MIT) formation, neutrophils die, but their undigested material remains inside MC vacuoles over days. MCs benefit from MIT formation, increasing their functional and metabolic fitness. Additionally, they are more pro-inflammatory and can exocytose active neutrophilic compounds with a time delay (nexocytosis), eliciting a type 1 interferon response in surrounding macrophages. Together, our study highlights neutrophil trapping and nexocytosis as MC-mediated processes, which may relay neutrophilic features over the course of chronic allergic inflammation.
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Molecular chaperones are critical for protein homeostasis and are implicated in several human pathologies such as neurodegeneration and cancer. While the binding of chaperones to nascent and misfolded proteins has been studied in great detail, the direct interaction between chaperones and RNA has not been systematically investigated. Here, we provide the evidence for widespread interaction between chaperones and RNA in human cells. We show that the major chaperone heat shock protein 70 (HSP70) binds to non-coding RNA transcribed by RNA polymerase III (RNA Pol III) such as tRNA and 5S rRNA. Global chromatin profiling revealed that HSP70 binds genomic sites of transcription by RNA Pol III. Detailed biochemical analyses showed that HSP70 alleviates the inhibitory effect of cognate tRNA transcript on tRNA gene transcription. Thus, our study uncovers an unexpected role of HSP70-RNA interaction in the biogenesis of a specific class of non-coding RNA with wider implications in cancer therapeutics.
Asunto(s)
Proteínas HSP70 de Choque Térmico , Neoplasias , Humanos , Proteínas HSP70 de Choque Térmico/genética , Proteínas HSP70 de Choque Térmico/metabolismo , Chaperonas Moleculares/metabolismo , ARN , ARN Polimerasa III/genética , ARN Polimerasa III/metabolismo , ARN de Transferencia/genética , ARN no Traducido/genéticaRESUMEN
In vitro-transcribed (IVT) mRNAs are modalities that can combat human disease, exemplified by their use as vaccines for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). IVT mRNAs are transfected into target cells, where they are translated into recombinant protein, and the biological activity or immunogenicity of the encoded protein exerts an intended therapeutic effect1,2. Modified ribonucleotides are commonly incorporated into therapeutic IVT mRNAs to decrease their innate immunogenicity3-5, but their effects on mRNA translation fidelity have not been fully explored. Here we demonstrate that incorporation of N1-methylpseudouridine into mRNA results in +1 ribosomal frameshifting in vitro and that cellular immunity in mice and humans to +1 frameshifted products from BNT162b2 vaccine mRNA translation occurs after vaccination. The +1 ribosome frameshifting observed is probably a consequence of N1-methylpseudouridine-induced ribosome stalling during IVT mRNA translation, with frameshifting occurring at ribosome slippery sequences. However, we demonstrate that synonymous targeting of such slippery sequences provides an effective strategy to reduce the production of frameshifted products. Overall, these data increase our understanding of how modified ribonucleotides affect the fidelity of mRNA translation, and although there are no adverse outcomes reported from mistranslation of mRNA-based SARS-CoV-2 vaccines in humans, these data highlight potential off-target effects for future mRNA-based therapeutics and demonstrate the requirement for sequence optimization.
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Sistema de Lectura Ribosómico , Seudouridina , ARN Mensajero , Animales , Humanos , Ratones , Vacuna BNT162/efectos adversos , Vacuna BNT162/genética , Vacuna BNT162/inmunología , Sistema de Lectura Ribosómico/genética , ARN Mensajero/química , ARN Mensajero/genética , ARN Mensajero/metabolismo , Seudouridina/análogos & derivados , Seudouridina/metabolismo , Ribosomas/metabolismo , Biosíntesis de ProteínasRESUMEN
During the translation surveillance mechanism known as ribosome-associated quality control, the ASC-1 complex (ASCC) disassembles ribosomes stalled on the mRNA. Here, we show that there are two distinct classes of stalled ribosome. Ribosomes stalled by translation elongation inhibitors or methylated mRNA are short lived in human cells because they are split by the ASCC. In contrast, although ultraviolet light and 4-nitroquinoline 1-oxide induce ribosome stalling by damaging mRNA, and the ASCC is recruited to these stalled ribosomes, we found that they are refractory to the ASCC. Consequently, unresolved UV- and 4NQO-stalled ribosomes persist in human cells. We show that ribosome stalling activates cell-cycle arrest, partly through ZAK-p38MAPK signaling, and that this cell-cycle delay is prolonged when the ASCC cannot resolve stalled ribosomes. Thus, we propose that the sensitivity of stalled ribosomes to the ASCC influences the kinetics of stall resolution, which in turn controls the adaptive stress response.
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Daño del ADN , Ribosomas , Humanos , Biosíntesis de Proteínas , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ribosomas/genética , Ribosomas/metabolismoRESUMEN
In response to stress, human cells coordinately downregulate transcription and translation of housekeeping genes. To downregulate transcription, the negative elongation factor (NELF) is recruited to gene promoters impairing RNA polymerase II elongation. Here we report that NELF rapidly forms nuclear condensates upon stress in human cells. Condensate formation requires NELF dephosphorylation and SUMOylation induced by stress. The intrinsically disordered region (IDR) in NELFA is necessary for nuclear NELF condensation and can be functionally replaced by the IDR of FUS or EWSR1 protein. We find that biomolecular condensation facilitates enhanced recruitment of NELF to promoters upon stress to drive transcriptional downregulation. Importantly, NELF condensation is required for cellular viability under stressful conditions. We propose that stress-induced NELF condensates reported here are nuclear counterparts of cytosolic stress granules. These two stress-inducible condensates may drive the coordinated downregulation of transcription and translation, likely forming a critical node of the stress survival strategy.
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Respuesta al Choque Térmico/genética , Proteínas Intrínsecamente Desordenadas/genética , Procesamiento Proteico-Postraduccional , ARN Polimerasa II/genética , Transcripción Genética , Factores de Elongación Transcripcional/genética , Aminoaciltransferasas/genética , Aminoaciltransferasas/metabolismo , Cromatina/química , Cromatina/metabolismo , Células Clonales , Quinasa 9 Dependiente de la Ciclina/genética , Quinasa 9 Dependiente de la Ciclina/metabolismo , Genes Reporteros , Células HEK293 , Células HeLa , Humanos , Proteínas Intrínsecamente Desordenadas/química , Proteínas Intrínsecamente Desordenadas/metabolismo , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Fosforilación , Factor B de Elongación Transcripcional Positiva/genética , Factor B de Elongación Transcripcional Positiva/metabolismo , Regiones Promotoras Genéticas , ARN Polimerasa II/metabolismo , Transducción de Señal , Estrés Fisiológico , Sumoilación , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Factores de Elongación Transcripcional/química , Factores de Elongación Transcripcional/metabolismo , Proteína Fluorescente RojaRESUMEN
The molecular chaperone Heat shock protein 90 (Hsp90) promotes the maturation of several important proteins and plays a key role in development, cancer progression, and evolutionary diversification. By mapping chromatin-binding sites of Hsp90 at high resolution across the Drosophila genome, we uncover an unexpected mechanism by which Hsp90 orchestrates cellular physiology. It localizes near promoters of many coding and noncoding genes including microRNAs. Using computational and biochemical analyses, we find that Hsp90 maintains and optimizes RNA polymerase II pausing via stabilization of the negative elongation factor complex (NELF). Inhibition of Hsp90 leads to upregulation of target genes, and Hsp90 is required for maximal activation of paused genes in Drosophila and mammalian cells in response to environmental stimuli. Our findings add a molecular dimension to the chaperone's functionality with wide ramifications into its roles in health, disease, and evolution.
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Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Proteínas de Choque Térmico/metabolismo , ARN Polimerasa II/metabolismo , Transcripción Genética , Animales , Drosophila melanogaster/genética , Ecdisona/metabolismo , Regulación de la Expresión Génica , HumanosRESUMEN
Cells experiencing proteotoxic stress downregulate the expression of thousands of active genes and upregulate a few stress-response genes. The strategy of downregulating gene expression has conceptual parallels with general lockdown in the global response to the coronavirus disease 2019 (COVID-19) pandemic. The mechanistic details of global transcriptional downregulation of genes, termed stress-induced transcriptional attenuation (SITA), are only beginning to emerge. The reduction in RNA and protein production during stress may spare proteostasis capacity, allowing cells to divert resources to control stress-induced damage. Given the relevance of translational downregulation in a broad variety of diseases, the role of SITA in diseases caused by proteotoxicity should be investigated in future, paving the way for potential novel therapeutics.
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COVID-19 , Control de Enfermedades Transmisibles , Humanos , ProteínasRESUMEN
Amyotrophic lateral sclerosis (ALS) is a fatal and incurable neurodegenerative disease affecting motor neurons and characterized by microglia-mediated neurotoxic inflammation whose underlying mechanisms remain incompletely understood. In this work, we reveal that MAPK/MAK/MRK overlapping kinase (MOK), with an unknown physiological substrate, displays an immune function by controlling inflammatory and type-I interferon (IFN) responses in microglia which are detrimental to primary motor neurons. Moreover, we uncover the epigenetic reader bromodomain-containing protein 4 (Brd4) as an effector protein regulated by MOK, by promoting Ser492-phospho-Brd4 levels. We further demonstrate that MOK regulates Brd4 functions by supporting its binding to cytokine gene promoters, therefore enabling innate immune responses. Remarkably, we show that MOK levels are increased in the ALS spinal cord, particularly in microglial cells, and that administration of a chemical MOK inhibitor to ALS model mice can modulate Ser492-phospho-Brd4 levels, suppress microglial activation, and modify the disease course, indicating a pathophysiological role of MOK kinase in ALS and neuroinflammation.
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Esclerosis Amiotrófica Lateral , Proteínas que Contienen Bromodominio , Proteínas Quinasas Activadas por Mitógenos , Enfermedades Neurodegenerativas , Animales , Ratones , Esclerosis Amiotrófica Lateral/metabolismo , Modelos Animales de Enfermedad , Microglía/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Proteínas Nucleares/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Proteínas que Contienen Bromodominio/genética , Proteínas que Contienen Bromodominio/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismoRESUMEN
Several independent studies in the last few years have suggested that phase separation and biomolecular condensation play a critical role in regulating different transcription steps from initiation to pausing and elongation. However, how components of the transcription machinery translocate among different types of condensates during transcription remains poorly understood. Guo et al have now identified a potential mechanism underlying translocation of the DSIF complex from pausing to elongation condensates during promoter pause release, as reported in this issue of EMBO reports.
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ARN Polimerasa II , Factores de Transcripción , Factores de Transcripción/genética , ARN Polimerasa II/metabolismo , Proteínas Nucleares/metabolismo , Núcleo Celular/metabolismo , Transcripción GenéticaRESUMEN
Protein aggregation is associated with neurodegeneration and various other pathologies. How specific cellular environments modulate the aggregation of disease proteins is not well understood. Here, we investigated how the endoplasmic reticulum (ER) quality control system handles ß-sheet proteins that were designed de novo to form amyloid-like fibrils. While these proteins undergo toxic aggregation in the cytosol, we find that targeting them to the ER (ER-ß) strongly reduces their toxicity. ER-ß is retained within the ER in a soluble, polymeric state, despite reaching very high concentrations exceeding those of ER-resident molecular chaperones. ER-ß is not removed by ER-associated degradation (ERAD) but interferes with ERAD of other proteins. These findings demonstrate a remarkable capacity of the ER to prevent the formation of insoluble ß-aggregates and the secretion of potentially toxic protein species. Our results also suggest a generic mechanism by which proteins with exposed ß-sheet structure in the ER interfere with proteostasis.
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Proteínas Amiloidogénicas/metabolismo , Degradación Asociada con el Retículo Endoplásmico/fisiología , Retículo Endoplásmico/metabolismo , Agregación Patológica de Proteínas/prevención & control , Línea Celular Tumoral , Células HEK293 , Células HeLa , Humanos , Chaperonas Moleculares/metabolismo , Agregación Patológica de Proteínas/patología , Conformación Proteica en Lámina beta/fisiología , Pliegue de Proteína , Interferencia de ARN , ARN Interferente Pequeño/genética , Respuesta de Proteína Desplegada/fisiologíaRESUMEN
Pluripotent stem cells are invaluable resources to study development and disease, holding a great promise for regenerative medicine. Here we use human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) from patients with Huntington's disease (HD-iPSCs) to shed light into the normal function of huntingtin (HTT) and its demise in disease. We find that HTT binds ATF7IP, a regulator of the histone H3 methyltransferase SETDB1. HTT inhibits the interaction of the ATF7IP-SETDB1 complex with other heterochromatin regulators and transcriptional repressors, maintaining low levels of H3K9 trimethylation (H3K9me3) in hESCs. Loss of HTT promotes global increased H3K9me3 levels and enrichment of H3K9me3 marks at distinct genes, including transcriptional regulators of neuronal differentiation. Although these genes are normally expressed at low amounts in hESCs, HTT knockdown (KD) reduces their induction during neural differentiation. Notably, mutant expanded polyglutamine repeats in HTT diminish its interaction with ATF7IP-SETDB1 complex and trigger H3K9me3 in HD-iPSCs. Conversely, KD of ATF7IP in HD-iPSCs reduces H3K9me3 alterations and ameliorates gene expression changes in their neural counterparts. Taken together, our results indicate ATF7IP as a potential target to correct aberrant H3K9me3 levels induced by mutant HTT.
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Proteína Huntingtina/genética , Enfermedad de Huntington/genética , Proteína Metiltransferasas/genética , Factores de Transcripción/genética , Diferenciación Celular/genética , Células Madre Embrionarias/metabolismo , Células Madre Embrionarias/patología , Regulación del Desarrollo de la Expresión Génica , Técnicas de Silenciamiento del Gen , Heterocromatina/genética , Histona Metiltransferasas/genética , N-Metiltransferasa de Histona-Lisina , Humanos , Enfermedad de Huntington/patología , Células Madre Pluripotentes Inducidas/metabolismo , Células Madre Pluripotentes Inducidas/patología , Lentivirus/genética , Neuronas/metabolismo , Neuronas/patología , Péptidos/genética , Proteínas RepresorasRESUMEN
Cis-regulatory regions (CRR) control gene expression and chromatin modifications. Genetic variation at CRR in individuals across a population contributes to phenotypic differences of biomedical relevance. This standing variation is important for personalized genomic medicine as well as for adaptive evolution and speciation. This review focuses on genetic variation at CRR, its influence on chromatin, gene expression, and ultimately disease phenotypes. In addition, we summarize our understanding of how this variation may contribute to evolution. Recent technological and computational advances have accelerated research in the direction of personalized medicine, combining strengths of molecular biology and genomics. This will pave new ways to understand how CRR variation affects phenotypes and chart out possible avenues of intervention.
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Cromatina/patología , Biología Computacional , Evolución Molecular , Medicina de Precisión , Elementos de Respuesta , Animales , Cromatina/genética , HumanosRESUMEN
The Photo-Activatable Ribonucleoside-enhanced CrossLinking and ImmunoPrecipitation (PAR-CLIP) method was recently developed for global identification of RNAs interacting with proteins. The strength of this versatile method results from induction of specific T to C transitions at sites of interaction. However, current analytical tools do not distinguish between non-experimentally and experimentally induced transitions. Furthermore, geometric properties at potential binding sites are not taken into account. To surmount these shortcomings, we developed a two-step algorithm consisting of a non-parametric two-component mixture model and a wavelet-based peak calling procedure. Our algorithm can reduce the number of false positives up to 24% thereby identifying high confidence interaction sites. We successfully employed this approach in conjunction with a modified PAR-CLIP protocol to study the functional role of nuclear Moloney leukemia virus 10, a putative RNA helicase interacting with Argonaute2 and Polycomb. Our method, available as the R package wavClusteR, is generally applicable to any substitution-based inference problem in genomics.
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Algoritmos , Modelos Estadísticos , ARN Helicasas/metabolismo , Proteínas de Unión al ARN/metabolismo , ARN/metabolismo , Análisis de Ondículas , Teorema de Bayes , Sitios de Unión , Células HEK293 , Humanos , Inmunoprecipitación/métodos , ARN/química , Análisis de Secuencia de ARNRESUMEN
Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is a widely used technique for genome-wide mapping of protein-DNA interactions and epigenetic marks in vivo. Recent studies have suggested an important role of heat shock protein 90 (Hsp90) in chromatin. This molecular chaperone assists other proteins to acquire their mature and functional conformation and helps in the assembly of many complexes. In this chapter, we provide specific details on how to perform Hsp90 ChIP-seq from Drosophila Schneider (S2) cells. Briefly, cells are simultaneously lyzed and reversibly cross-linked to stabilize protein-DNA interactions. Chromatin is prepared from isolated nuclei and sheared by sonication. Hsp90-bound loci are immunoprecipitated and the corresponding DNA fragments are purified and sequenced. The described approach revealed that Hsp90 binds close to the transcriptional start site of around one-third of all Drosophila coding genes and characterized the role of the chaperone at chromatin.
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Cromatina , ADN , Animales , Cromatina/genética , ADN/metabolismo , Inmunoprecipitación de Cromatina/métodos , Drosophila/genética , Drosophila/metabolismo , Proteínas HSP90 de Choque Térmico/genética , Secuenciación de Nucleótidos de Alto RendimientoRESUMEN
Hsp90 is a molecular chaperone responsible for regulating proteostasis under physiological and pathological conditions. Its central role in a range of diseases and potential as a drug target has focused efforts to understand its mechanisms and biological functions and to identify modulators that may form the basis for therapies. The 10th international conference on the Hsp90 chaperone machine was held in Switzerland in October 2022. The meeting was organized by Didier Picard (Geneva, Switzerland) and Johannes Buchner (Garching, Germany) with an advisory committee of Olivier Genest, Mehdi Mollapour, Ritwick Sawarkar, and Patricija van Oosten-Hawle. This was a much anticipated first in-person meeting of the Hsp90 community since 2018 after the COVID-19 pandemic led to the postponement of the 2020 meeting. The conference remained true to the tradition of sharing novel data ahead of publication, providing unparalleled depth of insight for both experts and newcomers to the field.
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COVID-19 , Pandemias , Humanos , Suiza , Unión Proteica , Chaperonas Moleculares/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismoRESUMEN
Our current understanding of biomolecular condensate formation is largely based on observing the final near-equilibrium condensate state. Despite expectations from classical nucleation theory, pre-critical protein clusters were recently shown to form under subsaturation conditions in vitro; if similar long-lived clusters comprising more than a few molecules are also present in cells, our understanding of the physical basis of biological phase separation may fundamentally change. Here, we combine fluorescence microscopy with photobleaching analysis to quantify the formation of clusters of NELF proteins in living, stressed cells. We categorise small and large clusters based on their dynamics and their response to p38 kinase inhibition. We find a broad distribution of pre-condensate cluster sizes and show that NELF protein cluster formation can be explained as non-classical nucleation with a surprisingly flat free-energy landscape for a wide range of sizes and an inhibition of condensation in unstressed cells.
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Cognición , Proteínas , Diagnóstico por ImagenRESUMEN
Upon progesterone stimulation, Endometrial Stromal Cells (EnSCs) undergo a differentiation program into secretory cells (decidualization) to release in abundance factors crucial for embryo implantation. We previously demonstrated that decidualization requires massive reshaping of the secretory pathway and, in particular, of the Golgi complex. To decipher the underlying mechanisms, we performed a time-course transcriptomic analysis of in vitro decidualizing EnSC. Pathway analysis shows that Gene Ontology terms associated with vesicular trafficking and early secretory pathway compartments are the most represented among those enriched for upregulated genes. Among these, we identified a cluster of co-regulated genes that share CREB3L1 and CREB3L2 binding elements in their promoter regions. Indeed, both CREB3L1 and CREB3L2 transcription factors are up-regulated during decidualization. Simultaneous downregulation of CREB3L1 and CREB3L2 impairs Golgi enlargement, and causes dramatic changes in decidualizing EnSC, including Golgi fragmentation, collagen accumulation in dilated Endoplasmic Reticulum cisternae, and overall decreased protein secretion. Thus, both CREB3L1 and CREB3L2 are required for Golgi reshaping and efficient protein secretion, and, as such, for successful decidualization.
RESUMEN
The precise regulation of RNA Polymerase II (Pol II) transcription after genotoxic stress is crucial for proper execution of the DNA damage-induced stress response. While stalling of Pol II on transcription-blocking lesions (TBLs) blocks transcript elongation and initiates DNA repair in cis, TBLs additionally elicit a response in trans that regulates transcription genome-wide. Here we uncover that, after an initial elongation block in cis, TBLs trigger the genome-wide VCP-mediated proteasomal degradation of promoter-bound, P-Ser5-modified Pol II in trans. This degradation is mechanistically distinct from processing of TBL-stalled Pol II, is signaled via GSK3, and contributes to the TBL-induced transcription block, even in transcription-coupled repair-deficient cells. Thus, our data reveal the targeted degradation of promoter-bound Pol II as a critical pathway that allows cells to cope with DNA damage-induced transcription stress and enables the genome-wide adaptation of transcription to genotoxic stress.
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Glucógeno Sintasa Quinasa 3 , Transcripción Genética , Daño del ADN/genética , Reparación del ADN/genética , Glucógeno Sintasa Quinasa 3/metabolismo , ARN Polimerasa II/genética , ARN Polimerasa II/metabolismoRESUMEN
Nucleic acid and histone modifications critically depend on the tricarboxylic acid (TCA) cycle for substrates and cofactors. Although a few TCA cycle enzymes have been reported in the nucleus, the corresponding pathways are considered to operate in mitochondria. Here, we show that a part of the TCA cycle is operational also in the nucleus. Using 13C-tracer analysis, we identified activity of glutamine-to-fumarate, citrate-to-succinate, and glutamine-to-aspartate routes in the nuclei of HeLa cells. Proximity labeling mass spectrometry revealed a spatial vicinity of the involved enzymes with core nuclear proteins. We further show nuclear localization of aconitase 2 and 2-oxoglutarate dehydrogenase in mouse embryonic stem cells. Nuclear localization of the latter enzyme, which produces succinyl-CoA, changed from pluripotency to a differentiated state with accompanying changes in the nuclear protein succinylation. Together, our results demonstrate operation of an extended metabolic pathway in the nucleus, warranting a revision of the canonical view on metabolic compartmentalization.