RESUMEN
Stop codon readthrough events give rise to longer proteins, which may alter the protein's function, thereby generating short-lasting phenotypic variability from a single gene. In order to systematically assess the frequency and origin of stop codon readthrough events, we designed a library of reporters. We introduced premature stop codons into mScarlet, which enabled high-throughput quantification of protein synthesis termination errors in E. coli using fluorescent microscopy. We found that under stress conditions, stop codon readthrough may occur at rates as high as 80%, depending on the nucleotide context, suggesting that evolution frequently samples stop codon readthrough events. The analysis of selected reporters by mass spectrometry and RNA-seq showed that not only translation but also transcription errors contribute to stop codon readthrough. The RNA polymerase was more likely to misincorporate a nucleotide at premature stop codons. Proteome-wide detection of stop codon readthrough by mass spectrometry revealed that temperature regulated the expression of cryptic sequences generated by stop codon readthrough in E. coli. Overall, our findings suggest that the environment affects the accuracy of protein production, which increases protein heterogeneity when the organisms need to adapt to new conditions.
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Codón de Terminación , Proteínas de Escherichia coli , Escherichia coli , Biosíntesis de Proteínas , Escherichia coli/genética , Escherichia coli/metabolismo , Codón de Terminación/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Transcripción Genética , Codón sin Sentido/genética , ARN Polimerasas Dirigidas por ADN/metabolismo , ARN Polimerasas Dirigidas por ADN/genética , Regulación Bacteriana de la Expresión GénicaRESUMEN
Since their discovery, extracellular vesicles (EVs) have changed our view on how organisms interact with their extracellular world. EVs are able to traffic a diverse array of molecules across different species and even domains, facilitating numerous functions. In this study, we investigate EV production in Euryarchaeota, using the model organism Haloferax volcanii. We uncover that EVs enclose RNA, with specific transcripts preferentially enriched, including those with regulatory potential, and conclude that EVs can act as an RNA communication system between haloarchaea. We demonstrate the key role of an EV-associated small GTPase for EV formation in H. volcanii that is also present across other diverse evolutionary branches of Archaea. We propose the name, ArvA, for the identified family of archaeal vesiculating GTPases. Additionally, we show that two genes in the same operon with arvA (arvB and arvC) are also involved in EV formation. Both, arvB and arvC, are closely associated with arvA in the majority of other archaea encoding ArvA. Our work demonstrates that small GTPases involved in membrane deformation and vesiculation, ubiquitous in Eukaryotes, are also present in Archaea and are widely distributed across diverse archaeal phyla.
Asunto(s)
Euryarchaeota , Vesículas Extracelulares , Haloferax volcanii , Proteínas de Unión al GTP Monoméricas , Euryarchaeota/genética , Archaea/genética , ARN , Haloferax volcanii/genética , Vesículas Extracelulares/genéticaRESUMEN
CD1d is an atypical MHC class I molecule which binds endogenous and exogenous lipids and can activate natural killer T (NKT) cells through the presentation of lipid antigens. CD1d surveys different cellular compartments including the secretory and the endolysosomal pathway and broadly binds lipids through its two hydrophobic pockets. Purification of the transmembrane protein CD1d for the analysis of bound lipids is technically challenging as the use of detergents releases CD1d-bound lipids. To address these challenges, we have developed a novel approach based on Sortase A-dependent enzymatic release of CD1d at the cell surface of live mammalian cells, which allows for single step release and affinity tagging of CD1d for shotgun lipidomics. Using this system, we demonstrate that CD1d carrying the Sortase A recognition motif shows unimpaired subcellular trafficking through the secretory and endolysosomal pathway and is able to load lipids in these compartments and present them to NKT cells. Comprehensive shotgun lipidomics demonstrated that the spectrum and abundance of CD1d-associated lipids is not representative of the total cellular lipidome but rather characterized by preferential binding to long chain sphingolipids and glycerophospholipids. As such, sphingomyelin species recently identified as critical negative regulators of NKT cell activation, represented the vast majority of endogenous CD1d-associated lipids. Moreover, we observed that inhibition of endolysosomal trafficking of CD1d surprisingly did not affect the spectrum of CD1d-bound lipids, suggesting that the majority of endogenous CD1d-associated lipids load onto CD1d in the secretory rather than the endolysosomal pathway. In conclusion, we present a novel system for the analysis of CD1d-bound lipids in mammalian cells and provide new insight into the spectrum of CD1d-associated lipids, with important functional implications for NKT cell activation.
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Aminoaciltransferasas , Esfingomielinas , Animales , Antígenos CD1d/metabolismo , Proteínas Bacterianas , Cisteína Endopeptidasas , MamíferosRESUMEN
We studied the consequences of the long-term impact of remediated tailing ponds from the Tyrnyauz tungsten-molybdenum mining and processing factory on the environmental pollution and children living in the area. For more than 60 years, the factory has been engaged in the development of tungsten-molybdenum deposits by open-pit and mine methods and the enrichment of the extracted ore. More than 252,771 thousand tons of waste accumulated in its dumps and tailings ponds. This 170-hectare tailing pond contains more than 125 million tons of waste with arsenic, tungsten, molybdenum and other metals. To examine the possible accumulation of potentially toxic elements in children's bodies, we determined the content of heavy metals in drinking water and in the hair of children. An exfoliated buccal micronucleus test was used to determine the cytogenetic status of children. We did not find significant differences in the content of heavy metals inherent of a tailing pond in children's hair from polluted area compared to the control zone. In buccal cells of children living in the vicinity of the tailings pond, the total number of cytogenetic abnormalities was increased by 4.1 times, the total index of proliferation by 1.5 times, early destruction of the nucleus by 2 times and apoptosis by 1.2 times compared to the clean zone. Thus, we identified a genotoxic and cytotoxic effect on children living in the vicinity of the tailing ponds, which led to an increase in the number of children belonging to the medium- and high-risk groups. No correlations were found between the content of heavy metals in children's hair and the frequency of cells with cytogenetic abnormalities. Weak positive correlation was found between the content of manganese, zinc and copper in children's hair and the indicators of buccal epithelial cell proliferation.
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Metales Pesados , Contaminantes del Suelo , Humanos , Niño , Tungsteno/toxicidad , Molibdeno/toxicidad , Mucosa Bucal , Minería , Contaminación Ambiental , Metales Pesados/análisis , Aberraciones Cromosómicas , Monitoreo del Ambiente/métodos , Contaminantes del Suelo/análisisRESUMEN
Despite recent advances in immune-modulatory drugs, pharmacological therapies have been proven ineffective in severe presentations of multiple sclerosis (MS), including secondary progressive MS. At present, therapeutic interventions' performance is primarily focused on ameliorating symptoms to improve the patient's quality of life (QOL). Among complementary treatments, nutrition has been considered a decisive factor to control symptoms and enhance the wellness of MS patients. Although no special diets are associated with MS, the impact of diet and dietary supplements on the course of progressive forms of the disease has been studied during the last few years. Fatigue is among the most common and disabling symptoms reported by MS patients. Fatigue has been defined in the Multiple Sclerosis Council for Clinical Practice Guidelines (MSCCPG, 1998) as a "subjective lack of physical and/or mental energy that the individual perceives as an interference with habitual and desired activities". This study aimed to compare the psychometric functioning of the "Fatigue Severity Scale" (FSS) and the "Modified Fatigue Impact Scale" (MFIS) in our sample of people with MS. Specifically, during chronic treatment, the change in these two parameters with two vitamin-rich dietary supplements (Citozym® and Ergozym®) was evaluated. The impact of these nutritional supplements revealed differences in antioxidant and anti-inflammatory parameters among the volunteers in the treatment group, with a subsequent improvement in fatigue. In conclusion, the results obtained have confirmed the effectiveness of complementary nutritional therapies, evaluated essentially based on hematological biomarkers, through which it is possible to act on disability to improve the QOL of MS patients.
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Esclerosis Múltiple , Suplementos Dietéticos , Fatiga/etiología , Humanos , Esclerosis Múltiple/complicaciones , Esclerosis Múltiple Crónica Progresiva , Calidad de VidaRESUMEN
Our objectives were to stabilize a non-clinical suspension for use in toxicological studies and to develop methods to investigate the stability of the formulation in terms of salt disproportionation. The compound under research was a hydrochloride salt of a practically insoluble discovery compound ODM-203. The first of the three formulation approaches was a suspension prepared and stored at room temperature. The second formulation was stabilized by pH adjustment. In the third approach cooling was used to prevent salt disproportionation. 5 mg/mL aqueous suspension consisting of 20 mg/mL PVP/VA and 5 mg/mL Tween 80 was prepared for each of the approaches. The polymer was used as precipitation inhibitor to provide prolonged supersaturation while Tween 80 was used to enhance dissolution and homogeneity of the suspension. The consequences of salt disproportionation were studied by a small-scale in vitro dissolution method and by an in vivo pharmacokinetic study in rats. Our results show that disproportionation was successfully suppressed by applying cooling of the suspension in an ice bath at 2-8 °C. This procedure enabled us to proceed to the toxicological studies in rats. The in vivo study results obtained for the practically insoluble compound showed adequate exposures with acceptable variation at each dose level.
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Química Farmacéutica , Excipientes , Animales , Ácido Clorhídrico , Ratas , Solubilidad , SuspensionesRESUMEN
The shape of nanomaterials affects their colloidal properties, cellular uptake, and fate in the environment. The microbial origin and microenvironment can play a role in altering the shape of the nanomaterial. However, such studies have never been conducted. Here, we demonstrate that the selenium nanomaterials produced by Escherichia coli K-12 are stable and remain as BioSe-Nanospheres under thermophilic conditions, while those produced by anaerobic granular sludge transform to BioSe-Nanorods, due to a lower quantity of proteins coating these nanoparticles, which has been verified by proteomics analysis as well as using chemically synthesized selenium nanomaterials. Furthermore, the presence of Bacillus safensis JG-B5T transform the purified BioSe-Nanospheres produced by E. coli K-12 to BioSe-Nanorods, though they are not transformed in the absence of B. safensis JG-B5T. This is due to the production of peptidases by B. safensis JG-B5T that cleaves the protein coating the BioSe-Nanospheres produced by E. coli K-12, leading to their transformation to trigonal BioSe-Nanorods, which is the thermodynamically more stable state. These findings suggest that the fate of selenium and probably other redox-active elements released from the biological wastewater treatment units needs to be reevaluated and improved by including microbial criteria for better accuracy.
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Escherichia coli K12 , Nanoestructuras , Selenio , Bacillus , Escherichia coliRESUMEN
Proteomics research infrastructures and core facilities within the Core for Life alliance advocate for community policies for quality control to ensure high standards in proteomics services.
Asunto(s)
Proteómica , Espectrometría de MasasRESUMEN
Mutations in cis-regulatory elements play important roles for phenotypic changes during evolution. Eye degeneration in the blind mole rat (BMR; Nannospalax galili) and other subterranean mammals is significantly associated with widespread divergence of eye regulatory elements, but the effect of these regulatory mutations on eye development and function has not been explored. Here, we investigate the effect of mutations observed in the BMR sequence of a conserved noncoding element upstream of Tdrd7, a pleiotropic gene required for lens development and spermatogenesis. We first show that this conserved element is a transcriptional repressor in lens cells and that the BMR sequence partially lost repressor activity. Next, we recapitulated evolutionary changes in this element by precisely replacing the endogenous regulatory element in a mouse line by the orthologous BMR sequence with CRISPR-Cas9. Strikingly, this repressor replacement caused a more than 2-fold upregulation of Tdrd7 in the developing lens; however, increased mRNA level does not result in a corresponding increase in TDRD7 protein nor an obvious lens phenotype, possibly explained by buffering at the posttranscriptional level. Our results are consistent with eye degeneration in subterranean mammals having a polygenic basis where many small-effect mutations in different eye-regulatory elements collectively contribute to phenotypic differences.
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Evolución Molecular , Cristalino/metabolismo , Ratas Topo/genética , Elementos Reguladores de la Transcripción/genética , Ribonucleoproteínas/genética , Animales , Femenino , Cristalino/crecimiento & desarrollo , Masculino , Ratones Transgénicos , Ribonucleoproteínas/metabolismoRESUMEN
Weight loss in patients with cancer is caused by cancer cachexia and chemotherapy-induced nausea and vomiting. Recent developments in antiemetic drugs have substantially improved nausea and vomiting, but this intervention did not reduce weight loss and other more severe side effects of chemotherapy, like anorexia, weakness, cough, dyspnea, hemoptysis, and pain. This study aimed to investigate the effects of nutrition intervention with a food supplement, during chemotherapy in patients with advanced nonsquamous non-small cell lung cancer (NSCLC). Patients received individualized nutrition counseling by a registered dietitian and were provided with oral supplements of Texidrofolico® for 90 days. Bodyweight and the mentioned other side effects were evaluated at baseline and after 90 days of intervention. To assess the effects of this dietary supplement, a total of 30 patients were retrospectively enrolled as controls, and the bodyweight and change in side effects of chemotherapy were compared with those observed in 30 Texidrofolico®-treated patients. After 90-day intervention, by oral supplement of Texidrofolico®, the patients, during the course of cytotoxic chemotherapy, showed an improved quality of life and not significant weight and BMI loss respect the control group. Furthermore, the number of patients, treated with Texidrofolico® who maintained or increased their body weight, after 90 days of treatment was significantly higher than in the control group. The effects of treatment with the food supplement have also been studied from a metabolic point of view. It was possible to find that one of the known markers of tumor growth, plasma polyamines, was reduced after the treatment. A possible relationship between these biogenic amines and the folate cycle is discussed. In conclusion, early intensive nutrition intervention with oral supplements of Texidrofolico® during chemotherapy of NSCLC patients prevents weight loss and it is beneficial for their quality of life.
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Peso Corporal , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Suplementos Dietéticos , Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos/dietoterapia , Neoplasias Pulmonares/tratamiento farmacológico , Pérdida de Peso , Anciano , Quimioterapia , Humanos , Persona de Mediana Edad , Estado Nutricional , Calidad de Vida , Estudios RetrospectivosRESUMEN
The human-specific gene ARHGAP11B is preferentially expressed in neural progenitors of fetal human neocortex and increases abundance and proliferation of basal progenitors (BPs), which have a key role in neocortex expansion. ARHGAP11B has therefore been implicated in the evolutionary expansion of the human neocortex, but its mode of action has been unknown. Here, we show that ARHGAP11B is imported into mitochondria, where it interacts with the adenine nucleotide translocase (ANT) and inhibits the mitochondrial permeability transition pore (mPTP). BP expansion by ARHGAP11B requires its presence in mitochondria, and pharmacological inhibition of ANT function or mPTP opening mimic BP expansion by ARHGAP11B. Searching for the underlying metabolic basis, we find that BP expansion by ARHGAP11B requires glutaminolysis, the conversion of glutamine to glutamate for the tricarboxylic acid (TCA) cycle. Hence, an ARHGAP11B-induced, mitochondria-based effect on BP metabolism that is a hallmark of highly mitotically active cells appears to underlie its role in neocortex expansion.
Asunto(s)
Proteínas Activadoras de GTPasa/metabolismo , Glutamina/metabolismo , Mitocondrias/metabolismo , Neocórtex/metabolismo , Células-Madre Neurales/metabolismo , Células 3T3 , Animales , Evolución Biológica , Proliferación Celular/genética , Ciclo del Ácido Cítrico , Proteínas Activadoras de GTPasa/genética , Regulación del Desarrollo de la Expresión Génica/genética , Ácido Glutámico/metabolismo , Humanos , Ratones , Translocasas Mitocondriales de ADP y ATP/metabolismo , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Poro de Transición de la Permeabilidad Mitocondrial , Neocórtex/embriología , Neurogénesis/genéticaRESUMEN
Understanding the impact of microorganisms on the mobility of selenium (Se) is important for predicting the fate of toxic Se in the environment and improving wastewater treatment technologies. The bacteria strain Bacillus safensis JG-B5T, isolated from soil in a uranium mining waste pile, can influence the Se speciation in the environment and engineered systems. However, the mechanism and conditions of this process remain unknown. This study found that the B. safensis JG-B5T is an obligate aerobic microorganism with an ability to reduce 70% of 2.5 mM selenite to produce red spherical biogenic elemental selenium nanoparticles (BioSeNPs). Only extracellular production of BioSeNPs was observed using transmission electron microscopy. The two-chamber reactor experiments, genome analysis and corona proteins identified on BioSeNPs suggested that the selenite reduction process was primarily mediated through membrane-associated proteins, like succinate dehydrogenase. Extracellular presence and low colloidal stability of BioSeNPs as indicated by ζ-potential measurements, render B. safensis JG-B5T an attractive candidate in wastewater treatment as it provides easy way of recovering Se while maintaining low Se discharge. As this microorganism decreases Se mobility, it will affect Se bioavailability in the environment and decreases its toxicity.
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Bacillus/metabolismo , Nanopartículas/metabolismo , Ácido Selenioso/metabolismo , Selenio/metabolismo , Bacillus/genética , Reactores Biológicos , Coloides , Filogenia , ARN Ribosómico 16S , ARN Ribosómico 23S , Ácido Selénico/metabolismoRESUMEN
The evolutionary expansion of the mammalian neocortex (Ncx) is thought to be linked to increased proliferative capacity of basal progenitors (BPs) and their neurogenic capacity. Here, by quantifying BP morphology in the developing Ncx of mouse, ferret, and human, we show that increased BP proliferative capacity is linked to an increase in BP process number. We identify human membrane-bound PALMDELPHIN (PALMD-Caax) as an underlying factor, and we show that it drives BP process growth and proliferation when expressed in developing mouse and ferret Ncx. Conversely, CRISPR/Cas9-mediated disruption of PALMD or its binding partner ADDUCIN-γ in fetal human Ncx reduces BP process numbers and proliferation. We further show that PALMD-induced processes enable BPs to receive pro-proliferative integrin-dependent signals. These findings provide a link between BP morphology and proliferation, suggesting that changes in BP morphology may have contributed to the evolutionary expansion of the Ncx.
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Neocórtex/anatomía & histología , Neocórtex/citología , Células-Madre Neurales/citología , Neuronas/citología , Animales , Proliferación Celular , Células Cultivadas , Hurones , Humanos , Integrinas/metabolismo , Ratones , Ratones Endogámicos C57BL , Neocórtex/metabolismo , Células-Madre Neurales/metabolismo , Neuronas/metabolismo , Transducción de SeñalRESUMEN
The role of aquatic resources in ancient economies and paleodiet is important for understanding the evolution of prehistorical societies. Charred food remains from ancient pottery are valuable molecular evidence of dietary habits in antiquity. However, conventional archaeometric approaches applied in their analysis lack organismal specificity, are affected by abundant environmental contaminants, do not elucidate food processing recipes and are limited in the inland regions where diverse dietary resources are available. We performed proteomics analysis of charred organic deposits adhered on early ceramics from Mesolithic-Neolithic inland site Friesack 4 (Brandenburg, Germany). One of pots-a small coarse bowl radiocarbon dated to the end of the 5th millennium BC-was attributed to Endmesolithic pottery. Proteomics of foodcrust from this vessel identified fine carp roe meal and revealed details of a prehistorical culinary recipe. Ancient proteins were unequivocally distinguished from contemporary contaminants by computing deamidation ratios of glutamine residues. These data paint a broader picture of the site-specific exploitation of aquatic resources and contribute to better understanding of the dietary context of Neolithic transition in European inland.
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Arqueología , Dieta , Peces , Proteómica , Secuencia de Aminoácidos , Animales , Cerámica , AlemaniaRESUMEN
Shotgun analysis provides a quantitative snapshot of the lipidome composition of cells, tissues, or model organisms; however, it does not elucidate the spatial distribution of lipids. Here we demonstrate that shotgun analysis could quantify low-picomole amounts of lipids isolated by laser capture microdissection (LCM) of hundred micrometer-sized histological zones visualized at the cryosections of tissues. We identified metabolically distinct periportal (pp) and pericentral (pc) zones by immunostaining of 20 µm thick cryosections of a healthy mouse liver. LCM was used to ablate, catapult, and collect the tissue material from 10 to 20 individual zones covering a total area of 0.3-0.5 mm2 and containing ca. 500 cells. Top-down shotgun profiling relying upon computational stitching of 61 targeted selective ion monitoring ( t-SIM) spectra quantified more than 200 lipid species from 17 lipid classes including glycero- and glycerophospholipids, sphingolipids, cholesterol esters, and cholesterol. Shotgun LCM revealed the overall commonality of the full lipidome composition of pp and pc zones along with significant ( p < 0.001) difference in the relative abundance of 13 lipid species. Follow-up proteomics analyses of pellets recovered from an aqueous phase saved after the lipid extraction identified 13 known and 7 new protein markers exclusively present in pp or in pc zones and independently validated the specificity of their visualization, isolation, and histological assignment.
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Bioquímica/métodos , Captura por Microdisección con Láser/métodos , Lípidos/sangre , Hígado/citología , Animales , Humanos , Masculino , Ratones , ProteómicaRESUMEN
Limb amputation in the newt induces myofibers to dedifferentiate and re-enter the cell cycle to generate proliferative myogenic precursors in the regeneration blastema. Here we show that bone morphogenetic proteins (BMPs) and mature BMPs that have been further cleaved by serum proteases induce cell cycle entry by dedifferentiating newt muscle cells. Protease-activated BMP4/7 heterodimers that are present in serum strongly induced myotube cell cycle re-entry with protease cleavage yielding a 30-fold potency increase of BMP4/7 compared with canonical BMP4/7. Inhibition of BMP signaling via muscle-specific dominant-negative receptor expression reduced cell cycle entry in vitro and in vivo. In vivo inhibition of serine protease activity depressed cell cycle re-entry, which in turn was rescued by cleaved-mimic BMP. This work identifies a mechanism of BMP activation that generates blastema cells from differentiated muscle.
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Proteínas Morfogenéticas Óseas/farmacología , Ciclo Celular/efectos de los fármacos , Desdiferenciación Celular/efectos de los fármacos , Extremidades/fisiología , Células Musculares/citología , Péptido Hidrolasas/farmacología , Regeneración/efectos de los fármacos , Salamandridae/fisiología , Animales , Bovinos , Fibrinolisina/farmacología , Células HEK293 , Humanos , Células Musculares/efectos de los fármacos , Fibras Musculares Esqueléticas/efectos de los fármacos , Fibras Musculares Esqueléticas/metabolismo , Multimerización de Proteína/efectos de los fármacos , Receptores de Superficie Celular/metabolismo , Proteínas Recombinantes/farmacología , Fase S/efectos de los fármacos , Suero/metabolismo , Transducción de Señal/efectos de los fármacos , Proteínas Smad/metabolismo , Trombina/farmacologíaRESUMEN
Lamp illuminants evidence the exploitation of natural resources, animal and plant domestication, commerce, religious practices and nutrition of ancient populations. However, the physicochemical analysis of their major constituent-burned, degraded and aged mixture of triacylglycerols is imprecise and may lead to ambiguous interpretations. We applied proteomics to analyze fuel deposits from eight lamps dated by 6th to 8th centuries AD that were excavated at the Astana necropolis (Xinjiang, China) and determined their origin by identifying organism-specific proteins. Proteomics evidence corroborated and detailed the assignments of source organism relying upon comparative profiling of intact triacylglycerols by shotgun lipidomics. We found that ruminant (mostly, sheep) fat, cattle ghee and sesame oil were common combustibles in Astana and concluded that sesame as an oilseed appeared in China under Tang Dynasty concomitantly with the expansion of Buddhism.
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Proteínas/química , Proteómica , Aceite de Sésamo/química , Hollín/química , Animales , Bovinos , China , Historia Antigua , Humanos , Tinta , Paleontología , Proteínas/aislamiento & purificación , OvinosRESUMEN
The nano- and micropatterned biosilica cell walls of diatoms are remarkable examples of biological morphogenesis and possess highly interesting material properties. Only recently has it been demonstrated that biosilica-associated organic structures with specific nanopatterns (termed insoluble organic matrices) are general components of diatom biosilica. The model diatom Thalassiosira pseudonana contains three types of insoluble organic matrices: chitin meshworks, organic microrings, and organic microplates, the latter being described in the present study for the first time. To date, little is known about the molecular composition, intracellular assembly, and biological functions of organic matrices. Here we have performed structural and functional analyses of the organic microrings and organic microplates from T. pseudonana. Proteomics analysis yielded seven proteins of unknown function (termed SiMat proteins) together with five known silica biomineralization proteins (four cingulins and one silaffin). The location of SiMat1-GFP in the insoluble organic microrings and the similarity of tyrosine- and lysine-rich functional domains identifies this protein as a new member of the cingulin protein family. Mass spectrometric analysis indicates that most of the lysine residues of cingulins and the other insoluble organic matrix proteins are post-translationally modified by short polyamine groups, which are known to enhance the silica formation activity of proteins. Studies with recombinant cingulins (rCinY2 and rCinW2) demonstrate that acidic conditions (pH 5.5) trigger the assembly of mixed cingulin aggregates that have silica formation activity. Our results suggest an important role for cingulins in the biogenesis of organic microrings and support the hypothesis that this type of insoluble organic matrix functions in biosilica morphogenesis.
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Diatomeas/ultraestructura , Matriz Extracelular/metabolismo , Dióxido de Silicio/metabolismo , Pared Celular/química , Pared Celular/ultraestructura , Diatomeas/química , Matriz Extracelular/química , Dióxido de Silicio/químicaRESUMEN
Treslin helps to trigger the initiation of DNA replication by promoting integration of Cdc45 into the replicative helicase. Treslin is a key positive-regulatory target of cell-cycle control mechanisms; activation of Treslin by cyclin-dependent kinase is essential for the initiation of replication. Here we demonstrate that Treslin is also a critical locus for negative regulatory mechanisms that suppress initiation. We found that the checkpoint-regulatory kinase Chk1 associates specifically with a C-terminal domain of Treslin (designated TRCT). Mutations in the TRCT domain abolish binding of Chk1 to Treslin and thereby eliminate Chk1-catalyzed phosphorylation of Treslin. Significantly, abolition of the Treslin-Chk1 interaction results in elevated initiation of chromosomal DNA replication during an unperturbed cell cycle, which reveals a function for Chk1 during a normal S phase. This increase is due to enhanced loading of Cdc45 onto potential replication origins. These studies provide important insights into how vertebrate cells orchestrate proper initiation of replication.
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Proteínas de Ciclo Celular/metabolismo , Replicación del ADN , Proteínas Quinasas/metabolismo , Proteínas de Xenopus/metabolismo , Xenopus laevis/metabolismo , Animales , Sitios de Unión , Proteínas de Ciclo Celular/genética , Línea Celular Tumoral , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1) , Cromosomas/metabolismo , Células HEK293 , Humanos , Fosforilación , Proteínas de Xenopus/genética , Xenopus laevis/embriología , Xenopus laevis/genéticaRESUMEN
OBJECTIVES: The HIV restriction factor, SAMHD1 (SAM domain and HD domain-containing protein 1), is a triphosphohydrolase that degrades deoxyribonucleoside triphosphates (dNTPs). Mutations in SAMHD1 cause Aicardi-Goutières syndrome (AGS), an inflammatory disorder that shares phenotypic similarity with systemic lupus erythematosus, including activation of antiviral type 1 interferon (IFN). To further define the pathomechanisms underlying autoimmunity in AGS due to SAMHD1 mutations, we investigated the physiological properties of SAMHD1. METHODS: Primary patient fibroblasts were examined for dNTP levels, proliferation, senescence, cell cycle progression and DNA damage. Genome-wide transcriptional profiles were generated by RNA sequencing. Interaction of SAMHD1 with cyclin A was assessed by coimmunoprecipitation and fluorescence cross-correlation spectroscopy. Cell cycle-dependent phosphorylation of SAMHD1 was examined in synchronised HeLa cells and using recombinant SAMHD1. SAMHD1 was knocked down by RNA interference. RESULTS: We show that increased dNTP pools due to SAMHD1 deficiency cause genome instability in fibroblasts of patients with AGS. Constitutive DNA damage signalling is associated with cell cycle delay, cellular senescence, and upregulation of IFN-stimulated genes. SAMHD1 is phosphorylated by cyclin A/cyclin-dependent kinase 1 in a cell cycle-dependent manner, and its level fluctuates during the cell cycle, with the lowest levels observed in G1/S phase. Knockdown of SAMHD1 by RNA interference recapitulates activation of DNA damage signalling and type 1 IFN activation. CONCLUSIONS: SAMHD1 is required for genome integrity by maintaining balanced dNTP pools. dNTP imbalances due to SAMHD1 deficiency cause DNA damage, leading to intrinsic activation of IFN signalling. These findings establish a novel link between DNA damage signalling and innate immune activation in the pathogenesis of autoimmunity.