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Dengue virus (DENV) is a mosquito-borne flavivirus responsible for dengue disease, a major human health concern for which no specific therapies are available. Like other viruses, DENV relies heavily on the host cellular machinery for productive infection. In this study, we performed a genome-wide CRISPR-Cas9 screen using haploid HAP1 cells to identify host genes important for DENV infection. We identified DPM1 and -3, two subunits of the endoplasmic reticulum (ER) resident dolichol-phosphate mannose synthase (DPMS) complex, as host dependency factors for DENV and other related flaviviruses, such as Zika virus (ZIKV). The DPMS complex catalyzes the synthesis of dolichol-phosphate mannose (DPM), which serves as mannosyl donor in pathways leading to N-glycosylation, glycosylphosphatidylinositol (GPI) anchor biosynthesis, and C- or O-mannosylation of proteins in the ER lumen. Mutation in the DXD motif of DPM1, which is essential for its catalytic activity, abolished DPMS-mediated DENV infection. Similarly, genetic ablation of ALG3, a mannosyltransferase that transfers mannose to lipid-linked oligosaccharide (LLO), rendered cells poorly susceptible to DENV. We also established that in cells deficient for DPMS activity, viral RNA amplification is hampered and truncated oligosaccharides are transferred to the viral prM and E glycoproteins, affecting their proper folding. Overall, our study provides new insights into the host-dependent mechanisms of DENV infection and supports current therapeutic approaches using glycosylation inhibitors to treat DENV infection.IMPORTANCE Dengue disease, which is caused by dengue virus (DENV), has emerged as the most important mosquito-borne viral disease in humans and is a major global health concern. DENV encodes only few proteins and relies on the host cell machinery to accomplish its life cycle. The identification of the host factors important for DENV infection is needed to propose new targets for antiviral intervention. Using a genome-wide CRISPR-Cas9 screen, we identified DPM1 and -3, two subunits of the DPMS complex, as important host factors for the replication of DENV as well as other related viruses such as Zika virus. We established that DPMS complex plays dual roles during viral infection, both regulating viral RNA replication and promoting viral structural glycoprotein folding/stability. These results provide insights into the host molecules exploited by DENV and other flaviviruses to facilitate their life cycle.
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Sistemas CRISPR-Cas , Virus del Dengue/fisiología , Dengue/virología , Manosiltransferasas/metabolismo , Animales , Chlorocebus aethiops , Retículo Endoplásmico/metabolismo , Fibroblastos/metabolismo , Glicoproteínas/metabolismo , Glicosilación , Glicosilfosfatidilinositoles/metabolismo , Células HEK293 , Humanos , Manosa/química , Oligosacáridos/química , ARN Guía de Kinetoplastida/metabolismo , ARN Viral/química , Células Vero , Replicación ViralRESUMEN
BACKGROUND: RBM10 is an RNA binding protein involved in message stabilization and alternative splicing regulation. The objective of the research described herein was to identify novel targets of RBM10-regulated splicing. To accomplish this, we downregulated RBM10 in human cell lines, using small interfering RNAs, then monitored alternative splicing, using a reverse transcription-PCR screening platform. RESULTS: RBM10 knockdown (KD) provoked alterations in splicing events in 10-20% of the pre-mRNAs, most of which had not been previously identified as RBM10 targets. Hierarchical clustering of the genes affected by RBM10 KD revealed good conservation of alternative exon inclusion or exclusion across cell lines. Pathway annotation showed RAS signaling to be most affected by RBM10 KD. Of particular interest was the finding that splicing of SMN pre-mRNA, encoding the survival of motor neuron (SMN) protein, was influenced by RBM10 KD. Inhibition of RBM10 resulted in preferential expression of the full-length, exon 7 retaining, SMN transcript in four cancer cell lines and one normal skin fibroblast cell line. SMN protein is expressed from two genes, SMN1 and SMN2, but the SMN1 gene is homozygously disrupted in people with spinal muscular atrophy; as a consequence, all of the SMN that is expressed in people with this disease is from the SMN2 gene. Expression analyses using primary fibroblasts from control, carrier and spinal muscle atrophy donors demonstrated that RBM10 KD resulted in preferential expression of the full-length, exon 7 retaining, SMN2 transcript. At the protein level, upregulation of the full-length SMN2 was also observed. Re-expression of RBM10, in a stable RBM10 KD cancer cell line, correlated with a reversion of the KD effect, demonstrating specificity. CONCLUSION: Our work has not only expanded the number of pre-mRNA targets for RBM10, but identified RBM10 as a novel regulator of SMN2 alternative inclusion.
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Precursores del ARN/genética , Empalme del ARN , Proteínas de Unión al ARN/metabolismo , Empalme Alternativo , Línea Celular , Análisis por Conglomerados , Biología Computacional/métodos , Exones , Fibroblastos , Perfilación de la Expresión Génica , Humanos , Reproducibilidad de los Resultados , Transducción de Señal , Proteína 2 para la Supervivencia de la Neurona Motora/genética , Proteínas ras/metabolismoRESUMEN
Cordycepin (3' deoxyadenosine) has long been used in the study of in vitro assembled polyadenylation complexes, because it terminates the poly(A) tail and arrests the cleavage complex. It is derived from caterpillar fungi, which are highly prized in Chinese traditional medicine. Here we show that cordycepin specifically inhibits the induction of inflammatory mRNAs by cytokines in human airway smooth muscle cells without affecting the expression of control mRNAs. Cordycepin treatment results in shorter poly(A) tails, and a reduction in the efficiency of mRNA cleavage and transcription termination is observed, indicating that the effects of cordycepin on 3' processing in cells are similar to those described in in vitro reactions. For the CCL2 and CXCL1 mRNAs, the effects of cordycepin are post-transcriptional, with the mRNA disappearing during or immediately after nuclear export. In contrast, although the recruitment of RNA polymerase II to the IL8 promoter is also unaffected, the levels of nascent transcript are reduced, indicating a defect in transcription elongation. We show that a reporter construct with 3' sequences from a histone gene is unaffected by cordycepin, while CXCL1 sequences confer cordycepin sensitivity to the reporter, demonstrating that polyadenylation is indeed required for the effect of cordycepin on gene expression. In addition, treatment with another polyadenyation inhibitor and knockdown of poly(A) polymerase α also specifically reduced the induction of inflammatory mRNAs. These data demonstrate that there are differences in the 3' processing of inflammatory and housekeeping genes and identify polyadenylation as a novel target for anti-inflammatory drugs.
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Desoxiadenosinas/farmacología , Expresión Génica/efectos de los fármacos , Inflamación/genética , Inflamación/prevención & control , Poliadenilación/efectos de los fármacos , Animales , Antiinflamatorios no Esteroideos/farmacología , Línea Celular , Quimiocina CCL2/genética , Quimiocina CXCL1/genética , ARN Polimerasas Dirigidas por ADN/metabolismo , Células HeLa , Humanos , Inflamación/metabolismo , Mediadores de Inflamación/antagonistas & inhibidores , Mediadores de Inflamación/metabolismo , Interleucina-8/genética , Ratones , Miocitos del Músculo Liso/efectos de los fármacos , Miocitos del Músculo Liso/metabolismo , FN-kappa B/metabolismo , Células 3T3 NIH , Regiones Promotoras Genéticas , Estabilidad del ARN/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Músculos Respiratorios/efectos de los fármacos , Músculos Respiratorios/metabolismo , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
Background: Expansion of the scope of pharmacists' activities in hospital is associated with reductions in adverse events and drug-related readmissions. However, the breadth of hospital pharmacists' clinical activities varies widely across Ontario due to provisions in the provincial Public Hospitals Act. Few data exist defining expanded scope in institutions across Ontario. Objectives: The primary objective was to describe the scope of practice of hospital pharmacists in Ontario who were undertaking expanded clinical activities based on policies or medical directives. The secondary objectives included determining benefits, limitations, facilitators, and barriers associated with implementing these activities. Methods: A survey was sent to the pharmacy leadership of Groups A and B public hospitals across Ontario. The survey contained quantitative and qualitative questions focused on 3 domains of expanded-scope activities: adaptation, discontinuation, and renewal of medication orders; prescriptive authority; and drug monitoring. Results: Of 56 hospitals invited, 46 (82%) submitted a survey response, with 1 exclusion (due to no response on some mandatory questions). The most common expanded-scope activity was independent performance of therapeutic drug monitoring (71%, 32/45). Pharmacists had the authority to independently adapt, discontinue, or renew inpatient medication orders in 60% (27/45) of hospitals, and could independently initiate medication orders in 20% (9/45). Barriers to implementing expanded-scope activities included limited time and staffing. Facilitators included proactive leadership, demonstrated clinical value, and strong rapport with other health care providers. Conclusions: Many institutions in Ontario have established polices to expand pharmacists' clinical activities, but there is a great deal of variability in scope of practice. Advocacy at the provincial level to unify scope of practice will help to optimize patient outcomes.
Contexte: L'expansion du champ d'activité des pharmaciens à l'hôpital est associée à une réduction des événements indésirables et des réadmissions liées aux médicaments. Cependant, l'étendue des activités cliniques des pharmaciens d'hôpitaux en Ontario varie considérablement en raison des dispositions de la Loi sur les hôpitaux publics de l'Ontario. Il existe peu de données définissant une portée élargie dans les établissements de l'Ontario. Objectifs: L'objectif principal consistait à décrire le champ d'exercice des pharmaciens d'hôpitaux en Ontario qui entreprenaient des activités cliniques élargies en fonction de politiques ou de directives médicales. Les objectifs secondaires comprenaient la définition des avantages, des limites, des facilitateurs et des obstacles associés à la mise en Åuvre de ces activités. Méthodes: Un sondage a été envoyé aux responsables des pharmacies des hôpitaux publics des groupes A et B de l'Ontario. Il comprenait des questions quantitatives et qualitatives axées sur 3 domaines d'activités liés à une portée élargie: l'adaptation, l'interruption et le renouvellement des ordonnances de médicaments; le pouvoir prescriptif; et la surveillance des médicaments. Résultats: Sur 56 hôpitaux invités, 46 (82 %) ont soumis une réponse au sondage, avec 1 exclusion (en raison de l'absence de réponse à certaines questions obligatoires). L'activité à portée élargie la plus courante était la réalisation indépendante de la surveillance thérapeutique des médicaments (32/45, 71 %). Les pharmaciens avaient la capacité d'adapter, d'interrompre ou de renouveler de manière indépendante les ordonnances de médicaments pour les patients hospitalisés dans 60 % (27/45) des hôpitaux, et pouvaient les initier de manière indépendante dans 20 % (9/45) des hôpitaux. Les obstacles à la mise en Åuvre d'activités à portée élargie comprenaient le manque de temps et de personnel. Les éléments facilitant la mise en Åuvre d'activités à portée élargie comprenaient le leadership proactif, la valeur clinique démontrée et les relations solides avec les autres prestataires de soins de santé. Conclusions: De nombreux établissements en Ontario ont établi des politiques liées à l'expansion des activités cliniques des pharmaciens, mais il existe une grande variabilité dans le champ d'exercice. Le plaidoyer au niveau provincial pour unifier le champ de pratique contribuera à optimiser les résultats pour les patients.
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PURPOSE: High-throughput screening (HTS) platforms have been widely used to identify candidate anticancer drugs and drug-drug combinations; however, HTS-based identification of new drug-ionizing radiation (IR) combinations has rarely been reported. Herein, we developed an integrated approach including cell-based HTS and computational large-scale isobolographic analysis to accelerate the identification of radiosensitizing compounds acting strongly and more specifically on cancer cells. METHODS AND MATERIALS: In a 384-well plate format, 160 compounds likely to interfere with the cell response to radiation were screened on human glioblastoma (U251-MG) and cervix carcinoma (ME-180) cell lines, as well as on normal fibroblasts (CCD-19Lu). After drug exposure, cells were irradiated or not and short-term cell survival was assessed by high-throughput cell microscopy. Computational large-scale dose-response and isobolographic approach were used to identify promising synergistic drugs radiosensitizing cancer cells rather than normal cells. Synergy of a promising compound was confirmed on ME-180 cells by an independent 96-well assay protocol, and finally, by the gold-standard colony forming assay. RESULTS: We retained 4 compounds synergistic at 2 isoeffects in U251-MG and ME-180 cell lines and 11 compounds synergistically effective in only one cancer cell line. Among these 15 promising radiosensitizers, 5 compounds showed limited toxicity combined or not with IR on normal fibroblasts. CONCLUSIONS: Overall, this study demonstrated that HTS chemoradiation screening together with large-scale computational analysis is an efficient tool to identify synergistic drug-IR combinations, with concomitant assessment of unwanted toxicity on normal fibroblasts. It sparks expectations to accelerate the discovery of highly desired agents improving the therapeutic index of radiation therapy.
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Antineoplásicos , Neoplasias , Fármacos Sensibilizantes a Radiaciones , Femenino , Humanos , Ensayos Analíticos de Alto Rendimiento/métodos , Detección Precoz del Cáncer , Fármacos Sensibilizantes a Radiaciones/farmacología , Antineoplásicos/farmacología , Línea Celular , Línea Celular TumoralRESUMEN
Membrane-less organelles are condensates formed by phase separation whose functions often remain enigmatic. Upon oxidative stress, PML scaffolds Nuclear Bodies (NBs) to regulate senescence or metabolic adaptation. PML NBs recruit many partner proteins, but the actual biochemical mechanism underlying their pleiotropic functions remains elusive. Similarly, PML role in embryonic stem cell (ESC) and retro-element biology is unsettled. Here we demonstrate that PML is essential for oxidative stress-driven partner SUMO2/3 conjugation in mouse ESCs (mESCs) or leukemia, a process often followed by their poly-ubiquitination and degradation. Functionally, PML is required for stress responses in mESCs. Differential proteomics unravel the KAP1 complex as a PML NB-dependent SUMO2-target in arsenic-treated APL mice or mESCs. PML-driven KAP1 sumoylation enables activation of this key epigenetic repressor implicated in retro-element silencing. Accordingly, Pml-/- mESCs re-express transposable elements and display 2-Cell-Like features, the latter enforced by PML-controlled SUMO2-conjugation of DPPA2. Thus, PML orchestrates mESC state by coordinating SUMO2-conjugation of different transcriptional regulators, raising new hypotheses about PML roles in cancer.
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Arsénico , Sumoilación , Animales , Elementos Transponibles de ADN , Células Madre Embrionarias , Ratones , Cuerpos Nucleares , Factores de TranscripciónRESUMEN
The steady-state localization of Golgi-resident glycosylation enzymes in the Golgi apparatus depends on a balance between anterograde and retrograde transport. Using the Retention Using Selective Hooks (RUSH) assay and high-content screening, we identified small molecules that perturb the localization of Mannosidase II (ManII) used as a model cargo for Golgi resident enzymes. In particular, we found that two compounds known as EGFR tyrosine kinase inhibitors, namely BML-265 and Tyrphostin AG1478 disrupt Golgi integrity and abolish secretory protein transport of diverse cargos, thus inducing brefeldin A-like effects. Interestingly, BML-265 and Tyrphostin AG1478 affect Golgi integrity and transport in human cells but not in rodent cells. The effects of BML-265 are reversible since Golgi integrity and protein transport are quickly restored upon washout of the compounds. BML-265 and Tyrphostin AG1478 do not lead to endosomal tubulation suggesting that, contrary to brefeldin A, they do not target the trans-Golgi ARF GEF BIG1 and BIG2. They quickly induce COPI dissociation from Golgi membranes suggesting that, in addition to EGFR kinase, the cis-Golgi ARF GEF GBF1 might also be a target of these molecules. Accordingly, overexpression of GBF1 prevents the effects of BML-265 and Tyrphostin AG1478 on Golgi integrity.
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Using a cell-based assay monitoring differential protein transport in the secretory pathway coupled to high-content screening, we have identified three molecules that specifically reduce the delivery of the major co-receptor for HIV-1, CCR5, to the plasma membrane. They have no effect on the closely related receptors CCR1 and CXCR4. These molecules are also potent in primary macrophages as they markedly decrease HIV entry. At the molecular level, two of these molecules inhibit the critical palmitoylation of CCR5 and thereby block CCR5 in the early secretory pathway. Our results open a clear therapeutics avenue based on trafficking control and demonstrate that preventing HIV infection can be performed at the level of its receptor delivery.
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Infecciones por VIH/metabolismo , Infecciones por VIH/virología , VIH-1/patogenicidad , Transporte de Proteínas/fisiología , Receptores CCR5/metabolismo , Secuencia de Aminoácidos , Línea Celular , Línea Celular Tumoral , Células HEK293 , Células HeLa , Humanos , Macrófagos/metabolismo , Macrófagos/virología , Receptores CCR1/metabolismo , Receptores CXCR4/metabolismo , Vías Secretoras/fisiologíaRESUMEN
Purpose: Physiotherapists have been acknowledged as playing a vital role in the care of people living with chronic obstructive pulmonary disease (COPD), and this care includes providing patient education (PE). Yet very little is known about the issues critical to providing this PE. The purpose of this scoping review was to identify and map out the current knowledge about the content, processes, and overall effectiveness of the PE provided by physiotherapists for people living with COPD. Method: Using the guidelines developed by Arksey and O'Malley in 2005 and by Levac in 2010, key databases were searched. A total of 447 articles were identified and screened for the following inclusion criteria: adults living with COPD, published in English or French between 1995 and 2015, and describing the PE provided by physiotherapists. Fourteen studies matched these criteria. Results: In the majority of studies, both physiotherapists and nurses provided PE to patients. Common PE topics included energy conservation, exacerbations, and breathlessness. None of the studies included measures for evaluating the effectiveness of the PE. Conclusions: Even though physiotherapists routinely provide PE to people living with COPD, this PE varies substantially. The heterogeneity of the studies and lack of measures of effectiveness prevented them from providing any evidence-based recommendations for physiotherapists.
Objectif : les physiothérapeutes sont reconnus pour leur rôle capital dans les soins aux personnes qui sont atteintes d'une maladie pulmonaire obstructive chronique (MPOC), ce qui inclut l'éducation aux patients (ÉP). On ne sait pourtant pas grand-chose des enjeux essentiels à la prestation de cette ÉP. La présente analyse de portée visait à cerner et à schématiser les connaissances sur le contenu, les processus et l'efficacité globale de l'ÉP que transmettent les physiothérapeutes aux personnes atteintes d'une MPOC. Méthodologie : à l'aide des lignes directrices d'Arksey et O'Malley (2005) et de Levac (2010), les chercheurs ont exploré les principales bases de données. Au total, ils ont extrait et examiné 447 articles afin de déterminer s'ils respectaient les critères d'inclusion : adultes atteints d'une MPOC, publication en français ou en anglais entre 1995 et 2015, description de l'ÉP fournie par les physiothérapeutes. Quatorze études respectaient ces critères. Résultats : dans la majorité des études, tant les physiothérapeutes que les infirmières offraient de l'ÉP aux patients. Les thèmes courants incluaient la conservation de l'énergie, les exacerbations et l'essoufflement. Aucune étude ne comportait de mesures pour évaluer l'efficacité de l'ÉP. Conclusions : même si les physiothérapeutes offrent systématiquement de l'ÉP aux personnes atteintes d'une MPOC, cette éducation est extrêmement variable. À cause de l'hétérogénéité des études et de l'absence de mesures d'efficacité, les études ne pouvaient fournir de recommandations fondées sur des données probantes aux physiothérapeutes.
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SIGNIFICANCE: Cellular metabolic activity impacts the production of reactive oxygen species (ROS), both positively through mitochondrial oxidative processes and negatively by promoting the production of reducing agents (including NADPH and reduced glutathione). A defined metabolic state in cancer cells is critical for cell growth and long-term self-renewal, and such state is intrinsically associated with redox balance. Promyelocytic leukemia protein (PML) regulates several biological processes, at least in part, through its ability to control the assembly of PML nuclear bodies (PML NBs). Recent Advances: PML is oxidation-prone, and oxidative stress promotes NB biogenesis. These nuclear subdomains recruit many nuclear proteins and regulate their SUMOylation and other post-translational modifications. Some of these cargos-such as p53, SIRT1, AKT, and mammalian target of rapamycin (mTOR)-are key regulators of cell fate. PML was also recently shown to regulate oxidation. CRITICAL ISSUES: While it was long considered primarily as a tumor suppressor protein, PML-regulated metabolic switch uncovered that this protein could promote survival and/or stemness of some normal or cancer cells. In this study, we review the recent findings on this multifunctional protein. FUTURE DIRECTIONS: Studying PML scaffolding functions as well as its fine role in the activation of p53 or fatty acid oxidation will bring new insights in how PML could bridge oxidative stress, senescence, cell death, and metabolism. Antioxid. Redox Signal. 26, 432-444.
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Oxidación-Reducción , Estrés Oxidativo , Proteína de la Leucemia Promielocítica/metabolismo , Transducción de Señal , Animales , Autofagia , Metabolismo Energético , Humanos , Cuerpos de Inclusión Intranucleares/química , Cuerpos de Inclusión Intranucleares/genética , Cuerpos de Inclusión Intranucleares/metabolismo , Proteínas Nucleares/química , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteína de la Leucemia Promielocítica/química , Proteína de la Leucemia Promielocítica/genética , Unión Proteica , Dominios y Motivos de Interacción de Proteínas , Procesamiento Proteico-Postraduccional , Transporte de Proteínas , Especies Reactivas de Oxígeno/metabolismo , Sumoilación , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
We previously examined the expression of Rbm5 during myoblast differentiation and found significantly more protein in the early stages of skeletal myoblast differentiation than during the later stages. We decided to determine if this elevated level was necessary for differentiation. Our hypothesis was that if high levels of Rbm5 protein expression were necessary for the initiation of skeletal myoblast differentiation, then inhibition of expression would prevent differentiation. Our long-term objective is to inhibit Rbm5 expression and examine the effect on H9c2 differentiation. Towards this end, stable knockdown clones and transient knockdown populations were generated. Expression analyses in H9c2 myoblasts demonstrated significant Rbm5 messenger RNA (mRNA) inhibition but, surprisingly, no effect on RBM5 protein levels. Expression of the Rbm5 paralogue Rbm10 was examined in order to (a) ensure no off-target knockdown effect, and (b) investigate any possible compensatory effects. RBM10 protein levels were found to be elevated, in both the clonal and transiently transfected populations. These results suggest that myoblast RBM5 expression is regulated by a process that includes RNA sequestration and/or controlled translation, and that (a) RBM5 function is compensated for by RBM10, and/or (b) RBM5 regulates RBM10 expression. We have developed a model to describe our findings, and suggest further experiments for testing its validity. Since upregulation of Rbm10 might compensate for downregulated Rbm5, and consequently might mask any potential knockdown effect, it could lead to incorrect conclusions regarding the importance of Rbm5 for differentiation. It is therefore imperative to determine how both RBM5 and RBM10 protein expression is regulated.
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Proteínas de Ciclo Celular/biosíntesis , Proteínas de Ciclo Celular/genética , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica/genética , Mioblastos/citología , Proteínas Nucleares/biosíntesis , Proteínas de Unión al ARN/biosíntesis , Proteínas de Unión al ARN/genética , Activación Transcripcional/genética , Proteínas Supresoras de Tumor/biosíntesis , Proteínas Supresoras de Tumor/genética , Animales , Proteínas de Ciclo Celular/metabolismo , Diferenciación Celular/genética , Línea Celular , Proteínas de Unión al ADN/metabolismo , Perfilación de la Expresión Génica , Interferencia de ARN , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Proteínas de Unión al ARN/metabolismo , Ratas , Proteínas Supresoras de Tumor/metabolismoRESUMEN
Fasci et al proposed that a SENP1-mediated switch from SUMO2 to SUMO1 conjugation on Lys(65) in promyelocytic leukemia protein (PML) is required for arsenic-induced PML degradation, the basis for the antileukemic activity of arsenic. We found that PML or PML/RARA (retinoic acid receptor α) mutants that cannot be SUMO-conjugated on this specific site nevertheless underwent immediate arsenic-triggered SUMO modification. Moreover, these mutants were efficiently degraded in cells and even in vivo, demonstrating that SUMOylation of Lys(65) was dispensable for arsenic response. The existence and putative role of a SUMO switch on PML should thus be reassessed.
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Arsénico , Proteínas Nucleares/genética , Proteína de la Leucemia Promielocítica , Proteínas Supresoras de Tumor/genética , UbiquitinaciónRESUMEN
BACKGROUND: RBM10 is an RNA binding protein involved in the regulation of transcription, alternative splicing and message stabilization. Mutations in RBM10, which maps to the X chromosome, are associated with TARP syndrome, lung and pancreatic cancers. Two predominant isoforms of RBM10 exist, RBM10v1 and RBM10v2. Both variants have alternate isoforms that differ by one valine residue, at amino acid 354 (RBM10v1) or 277 (RBM10v2). It was recently observed that a novel point mutation at amino acid 354 of RBM10v1, replacing valine with glutamic acid, correlated with preferential expression of an exon 11 inclusion variant of the proliferation regulatory protein NUMB, which is upregulated in lung cancer. FINDINGS: We demonstrate, using the GLC20 male-derived small cell lung cancer cell line - confirmed to have only one X chromosome - that the two (+/-) valine isoforms of RBM10v1 and RBM10v2 result from alternative splicing. Protein modeling of the RNA Recognition Motif (RRM) within which the alteration occurs, shows that the presence of valine inhibits the formation of one of the two α-helices associated with RRM tertiary structure, whereas the absence of valine supports the α-helical configuration. We then show 2-fold elevated expression of the transcripts encoding the minus valine RBM10v1 isoform in GLC20 cells, compared to those encoding the plus valine isoform. This expression correlates with preferential expression of the lung cancer-associated NUMB exon 11 inclusion variant. CONCLUSIONS: Our observations suggest that the ability of RBM10v1 to regulate alternative splicing depends, at least in part, on a structural alteration within the second RRM domain, which influences whether RBM10v1 functions to support or repress splicing. A model is presented.
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Empalme Alternativo , Regulación Neoplásica de la Expresión Génica , Neoplasias Pulmonares/genética , Proteínas de la Membrana/genética , Proteínas del Tejido Nervioso/genética , ARN Mensajero/genética , Proteínas de Unión al ARN/genética , Carcinoma Pulmonar de Células Pequeñas/genética , Línea Celular Tumoral , Exones , Ácido Glutámico/genética , Ácido Glutámico/metabolismo , Humanos , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Masculino , Proteínas de la Membrana/metabolismo , Datos de Secuencia Molecular , Proteínas del Tejido Nervioso/metabolismo , Motivos de Nucleótidos , Mutación Puntual , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/metabolismo , Transducción de Señal , Carcinoma Pulmonar de Células Pequeñas/metabolismo , Carcinoma Pulmonar de Células Pequeñas/patología , Valina/genética , Valina/metabolismoRESUMEN
Centrosome amplification is a hallmark of human tumours. In flies, extra centrosomes cause spindle position defects that result in the expansion of the neural stem cell (NSC) pool and consequently in tumour formation. Here we investigated the consequences of centrosome amplification during mouse brain development and homeostasis. We show that centrosome amplification causes microcephaly due to inefficient clustering mechanisms, where NSCs divide in a multipolar fashion producing aneuploid cells that enter apoptosis. Importantly, we show that apoptosis inhibition causes the accumulation of highly aneuploid cells that lose their proliferative capacity and differentiate, thus depleting the pool of progenitors. Even if these conditions are not sufficient to halt brain development, they cause premature death due to tissue degeneration. Our results support an alternative concept to explain the etiology of microcephaly and show that centrosome amplification and aneuploidy can result in tissue degeneration rather than overproliferation and cancer.