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Several long-period radio transients have recently been discovered, with strongly polarized coherent radio pulses appearing on timescales between tens to thousands of seconds1,2. In some cases, the radio pulses have been interpreted as coming from rotating neutron stars with extremely strong magnetic fields, known as magnetars; the origin of other, occasionally periodic and less-well-sampled radio transients is still debated3. Coherent periodic radio emission is usually explained by rotating dipolar magnetic fields and pair-production mechanisms, but such models do not easily predict radio emission from such slowly rotating neutron stars and maintain it for extended times. On the other hand, highly magnetic isolated white dwarfs would be expected to have long spin periodicities, but periodic coherent radio emission has not yet been directly detected from these sources. Here we report observations of a long-period (21 min) radio transient, which we have labelled GPM J1839-10. The pulses vary in brightness by two orders of magnitude, last between 30 and 300 s and have quasiperiodic substructure. The observations prompted a search of radio archives and we found that the source has been repeating since at least 1988. The archival data enabled constraint of the period derivative to <3.6 × 10-13 s s-1, which is at the very limit of any classical theoretical model that predicts dipolar radio emission from an isolated neutron star.
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OBJECTIVE: Knowing the important repercussions of menopause for women's health and that female longevity can be better understood through studies based on aging biomarkers, studies on the relationship between menopause and telomere shortening may help to better understand this stage of life. This study aimed to analyze what research has been produced regarding the relationship between menopause and telomere length. METHODS: This integrative literature review included searches in PubMed, CINAHL, LILACS, Web of Science and Scopus databases. Four studies were selected for the final sample. RESULTS: The findings of these studies indicate that older age for menopause and longer reproductive life (difference between age at menopause and menarche) are associated with longer telomeres, that is, with longevity. CONCLUSION: The relationship between menopause and telomere length is uncertain. The small number of studies included in this review, and the fact that the results indicate that the relationship between menopause and telomere length may be dependent on the stage of the menopause and race/ethnicity, suggest that additional research focusing on these variables should be carried out.
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Inhibition of receptor-interacting protein kinase 1 (RIP1) has been recognized as a compelling tool for limiting necroptosis. Recent findings have indicated that RIP1 inhibitor, necrostatin-1 (Nec-1), is also able to modify heart function under non-cell death conditions. In this study, we investigated its underlying molecular mechanisms and compared with those of novel pharmacologically improved agents (Nec-1s and GSK'772) and its inactive analog (Nec-1i). Heart function was examined in Langendorff-perfused rat hearts. Certain proteins regulating myocardial contraction-relaxation cycle and oxidative stress (OS) were evaluated by immunoblotting and as the extent of lipid peroxidation, protein carbonylation and nitration, respectively. In spite of the increase of left ventricular developed pressure (LVDP) due to treatment by both Nec-1 and Nec-1i, only the former agent increased the phosphorylation of Ca2+/calmodulin-dependent protein kinase II delta (CaMKIIδ) at threonine 287 and cardiac myosin-binding protein-C (cMyBPc) at serine 282. In contrast, Nec-1s did not elicit such changes, while it also increased LVDP. GSK'772 activated CaMKIIδ-phospholamban (PLN) axis. Neither protein kinase A (PKA) nor its selected molecular targets, such as serine 16 phosphorylated PLN and sarco/endoplasmic reticulum Ca2+-ATPase 2a (SERCA2a), were affected by either RIP1 inhibitor. Nec-1, like other necrostatins (Nec-1i, Nec-1s), but not GSK'772, elevated protein tyrosine nitration without affecting other markers of OS. In conclusion, this study indicated for the first time that Nec-1 may affect basal heart function by the modulation of OS and activation of some proteins of contraction-relaxation cycle.
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Coração/efeitos dos fármacos , Imidazóis/farmacologia , Indóis/farmacologia , Contração Miocárdica , Necrose , Estresse Oxidativo , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Animais , Masculino , Ratos , Ratos Wistar , Proteína Serina-Treonina Quinases de Interação com ReceptoresRESUMO
Rheumatoid arthritis (RA) has been associated with osteoporosis. Quantitative computed tomography (QCT) is capable of assessing bone density and composition. We found lower bone density in RA compared to controls. Age and RA duration influenced bone density. QCT may be useful to assess bone metabolism in RA. INTRODUCTION: RA is associated with generalized and periarticular osteoporosis. In addition to DXA that determines areal bone mineral density (BMD), peripheral QCT also detects volumetric BMD. QCT differentiates between total, trabecular, and cortical BMD. Here, we compared DXA and QCT in RA patients and healthy controls. METHODS: BMD of 57 female RA patients and 32 age-matched healthy female controls were assessed by DXA. QCT of the forearm ultradistal region was also performed. Densitometry data were correlated with age, disease duration, disease activity, serum CRP, and anti-CCP levels. RESULTS: Total bone density (310.4 ± 79.7 versus 354.0 ± 54.1 mg/cm3; p = 0.007) and attenuation (0.37 ± 0.05 versus 0.40 ± 0.03 1/cm; p = 0.001), trabecular density (157.6 ± 57.0 versus 193.8 ± 48.7 mg/cm3; p = 0.005) and attenuation (0.28 ± 0.03 versus 0.32 ± 0.04 1/cm; p < 0.0001), and cortical density (434.3 ± 115.8 versus 492.5 ± 64.0 mg/cm3; p = 0.006) and attenuation (0.44 ± 0.07 versus 0.47 ± 0.04 1/cm; p = 0.004) were significantly lower in RA. Both lumbar and femoral neck BMD, as well as T-scores, were significantly lower in RA versus controls (p < 0.001 in all cases). In RA, total and cortical QCT attenuation and density were associated with age, the presence of RA, and their combination. In contrast, trabecular density and attenuation were only affected by the presence of the disease but not by age. Also in RA, total trabecular and cortical density as determined by QCT significantly correlated with lumbar and/or femoral neck BMD as measured by DXA. Finally, anti-CCP seropositivity was associated with lower trabecular density and attenuation. CONCLUSIONS: Both DXA and QCT may be suitable to study bone metabolism in RA. Areal BMD determined by DXA may correlate with volumetric bone density measured by QCT. Moreover, trabecular osteoporosis may be associated by the underlying autoimmune-inflammatory disease, while cortical osteoporosis may rather be age-related.
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Artrite Reumatoide/complicações , Densidade Óssea/fisiologia , Antebraço/fisiopatologia , Osteoporose/diagnóstico por imagem , Osteoporose/etiologia , Absorciometria de Fóton/métodos , Adulto , Fatores Etários , Idoso , Artrite Reumatoide/fisiopatologia , Estudos de Casos e Controles , Feminino , Colo do Fêmur/diagnóstico por imagem , Colo do Fêmur/fisiopatologia , Antebraço/diagnóstico por imagem , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/fisiopatologia , Pessoa de Meia-Idade , Osteoporose/fisiopatologia , Tomografia Computadorizada por Raios X/métodos , Adulto JovemRESUMO
UNLABELLED: The study demonstrates that wintertime surgeries are associated with impaired fracture healing and increases the risk of conversion to hip arthroplasty after osteosynthesis of femoral neck fracture. Furthermore, the results raise the possibility of association between seasonal changes in vitamin D levels and impaired fracture healing of femoral neck fracture. INTRODUCTION: Although the changes of vitamin D level and calcitropic hormones influencing bone metabolism are seasonal, the effect of seasons on hip fracture healing is unknown. We assessed the effects of seasonal periodicity on conversion to hip arthroplasty after primary osteosynthesis of femoral neck fracture. METHODS: This nationwide retrospective observational cohort study involved 2779 patients aged ≥ 60 years who underwent internal screw fixation for primary femoral neck fracture and were discharged in 2000. Cases requiring conversion to arthroplasty during the 8-year follow-up derived from the Hungarian health insurance database were registered. Risk factors assessed included sex, age, fracture type, season of primary surgery and surgical delay. Competing-risks regression analysis was used for data analyses. RESULTS: During the observation period, 190 conversions to hip arthroplasty (6.8%) were identified, yielding an overall incidence of 19.5 per 1000 person-years. The crude incidence rates of conversions after osteosynthesis in winter, spring, summer and fall were 28.6, 17.8, 16.9 and 14.7 per 1000 person-years, respectively. Besides younger age, female sex and intracapsular fracture displacement, wintertime primary osteosynthesis significantly increased the risk of conversion (fall vs. winter, hazard ratio (HR): 0.50, 95% confidence interval [95% CI 0.33-0.76]; spring vs. winter, HR: 0.63, [95% CI 0.44-0.92]; summer vs. winter, HR: 0.62, [95% CI 0.42-0.91]). CONCLUSIONS: Our study demonstrate that wintertime primary osteosynthesis increases the risk of conversion surgeries. The results may help improving the outcome of primary fixation of femoral neck fractures.
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Artroplastia de Quadril/estatística & dados numéricos , Fraturas do Colo Femoral/cirurgia , Fixação Interna de Fraturas/estatística & dados numéricos , Consolidação da Fratura , Estações do Ano , Idoso , Idoso de 80 Anos ou mais , Parafusos Ósseos , Feminino , Fixação Interna de Fraturas/métodos , Humanos , Incidência , Masculino , Reoperação/estatística & dados numéricos , Estudos Retrospectivos , Fatores de Risco , Resultado do TratamentoRESUMO
Petroleum aspiration as a reason for lipid pneumonia is a rare complication. Mostly children are affected and mortality rates are low. In most case series, virtually every subject survived.We describe here the case of a patient who developed ARDS and pneumatoceles with a fatal outcome. Due to the undulant nature of the disease, multipe thoracic CT were performed, enabling us to describe the precise radiologic course of the disease.
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Petróleo/intoxicação , Pneumonia Lipoide/induzido quimicamente , Pneumonia Lipoide/diagnóstico por imagem , Síndrome do Desconforto Respiratório/induzido quimicamente , Síndrome do Desconforto Respiratório/diagnóstico por imagem , Idoso , Diagnóstico Diferencial , Evolução Fatal , Humanos , MasculinoRESUMO
Leptin, a hormone secreted by adipocytes, regulates the size of the adipose tissue mass through effects on satiety and energy metabolism. Leptin's precise sites of action are not known. The leptin receptor (Ob-R) is found in many tissues in several alternatively spliced forms raising the possibility that leptin exerts effects on many tissues including the hypothalamus. Ob-R is a member of the gp130 family of cytokine receptors which are known to stimulate gene transcription via activation of cytosolic STAT proteins. In order to identify the sites of leptin action in vivo, we assayed for activation of STAT proteins in mice treated with leptin. The STAT proteins bind to phosphotyrosine residues in the cytoplasmic domain of the ligand-activated receptor where they are phosphorylated. The activated STAT proteins dimerize and translocate to the nucleus where they bind DNA and activate transcription. The activation of STAT proteins in response to leptin was assayed in a variety of mouse tissues known to express Ob-R. Leptin injection activated Stat3 but no other STAT protein in the hypothalamus of ob/ob and wild-type mice but not db/db mice, mutants that lack an isoform of the leptin receptor. Leptin did not induce STAT activation in any of the other tissues tested. Activation of Stat3 by leptin was dose dependent and first observed after 15 minutes and maximal at 30 minutes. Our data indicate the hypothalamus is a direct target of leptin action and that this activation is critically dependent on the gp-130-like leptin receptor isoform missing in C57BLKS/J db/db mice. This is the first in vivo demonstration of leptin signal transduction.
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Proteínas de Ligação a DNA/metabolismo , Hipotálamo/metabolismo , Proteínas/fisiologia , Receptores de Superfície Celular , Transativadores/metabolismo , Animais , Sequência de Bases , Proteínas de Transporte/metabolismo , Primers do DNA , Leptina , Camundongos , Camundongos Obesos , Dados de Sequência Molecular , Receptores para Leptina , Fator de Transcrição STAT3 , Transdução de Sinais , Fatores de TempoRESUMO
Despite the fact that bone mineral density (BMD) is an important fracture risk predictor in human medicine, studies in equine orthopedic research are still lacking. We hypothesized that BMD correlates with bone failure and fatigue fractures of this bone. Thus, the objectives of this study were to measure the structural and mechanical properties of the proximal phalanx with dual energy X-ray absorptiometry (DXA), to correlate the data obtained from DXA and computer tomography (CT) measurements to those obtained by loading pressure examination and to establish representative region of interest (ROI) for in vitro BMD measurements of the equine proximal phalanx for predicting bone failure force. DXA was used to measure the whole bone BMD and additional three ROI sites in 14 equine proximal phalanges. Following evaluation of the bone density, whole bone, cortical width and area in the mid-diaphyseal plane were measured on CT images. Bones were broken using a manually controlled universal bone crusher to measure bone failure force and reevaluated for the site of fractures on follow-up CT images. Compressive load was applied at a constant displacement rate of 2 mm/min until failure, defined as the first clear drop in the load measurement. The lowest BMD was measured at the trabecular region (mean +/- SD: 1.52 +/- 0.12 g/cm2; median: 1.48 g/cm2; range: 1.38-1.83 g/cm2). There was a significant positive linear correlation between trabelcular BMD and the breaking strength (P = 0.023, r = 0.62). The trabecular region of the proximal phalanx appears to be the only significant indicator of failure of strength in vitro. This finding should be reassessed to further reveal the prognostic value of trabecular BMD in an in vivo fracture risk model.
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Densidade Óssea/fisiologia , Fraturas Ósseas/veterinária , Cavalos , Tomografia Computadorizada por Raios X/veterinária , Absorciometria de Fóton , Animais , Fenômenos Biomecânicos , Cadáver , Força Compressiva , Membro AnteriorRESUMO
Diabetes mellitus is known to produce various cell-damaging events and thereby underlie heart dysfunction and remodeling. However, very little is known about its inflammation-associated pathomechanisms due to necrosis-like cell death. For this purpose, we aimed to investigate signaling pathways of necroptosis and pyroptosis, known to produce plasma membrane rupture with the resultant promotion of inflammation. One-year old Zucker diabetic fatty (ZDF) rats did not exhibit significant heart dysfunction as revealed by echocardiographic measurement. On the other hand, there was a decrease in heart rate due to diabetes. Immunoblotting analysis showed that the left ventricles of ZDF rats overexpress neither the main necroptotic proteins including receptor-interacting protein kinase 3 (RIP3) and mixed lineage domain kinase-like pseudokinase (MLKL), nor the pyroptotic regulators including NLR family pyrin domain containing 3 protein (NLRP3), caspase-1, interleukin-1 beta (IL-1beta and the N-terminal gasdermin D (GSDMD-N). On the other hand, the increased activation of the RIP3 kinase due to phosphorylation was found in such hearts. In summary, we showed for the first time that the activation of cardiac RIP3 is upregulated due to disturbances in glucose metabolism which, however, did not proceed to necrosis-like cell death. These data can indicate that the activated RIP3 might also underlie other pleiotropic, non-necroptotic signaling pathways under basal conditions.
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Diabetes Mellitus Tipo 2 , Piroptose , Ratos , Animais , Apoptose , Proteínas Quinases/metabolismo , Ratos Zucker , Necrose , Transdução de Sinais , InflamaçãoRESUMO
The STATs (signal transducers and activators of transcription) are latent cytoplasmic proteins that, upon activation by cell surface bound polypeptide ligands, move to the nucleus to direct transcription. A variety of protein-protein interactions that affect the function of STATs has been recently recognized. It has become clear that the STATs are functional mosaics, or mixtures of signal transduction and transcription modules.
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Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas Quinases Ativadas por Mitógeno , Transdução de Sinais , Transativadores/metabolismo , Animais , Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Humanos , Proteínas Quinases JNK Ativadas por Mitógeno , Fator de Transcrição STAT1 , Domínios de Homologia de srcRESUMO
Expression of Q205L Galphao (Galphao*), an alpha subunit of heterotrimeric guanine nucleotide-binding proteins (G proteins) that lacks guanosine triphosphatase (GTPase) activity in NIH-3T3 cells, results in transformation. Expression of Galphao* in NIH-3T3 cells activated signal transducer and activator of transcription 3 (Stat3) but not mitogen-activated protein (MAP) kinases 1 or 2. Coexpression of dominant negative Stat3 inhibited Galphao*-induced transformation of NIH-3T3 cells and activation of endogenous Stat3. Furthermore, Galphao* expression increased activity of the tyrosine kinase c-Src, and the Galphao*-induced activation of Stat3 was blocked by expression of Csk (carboxyl-terminal Src kinase), which inactivates c-Src. The results indicate that Stat3 can function as a downstream effector for Galphao* and mediate its biological effects.
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Transformação Celular Neoplásica , Proteínas de Ligação a DNA/metabolismo , Proteínas Heterotriméricas de Ligação ao GTP/metabolismo , Transativadores/metabolismo , Células 3T3 , Animais , Proteína Tirosina Quinase CSK , Linhagem Celular Transformada , Ativação Enzimática , Subunidades alfa de Proteínas de Ligação ao GTP , Genes Reporter , Proteínas Heterotriméricas de Ligação ao GTP/genética , Sistema de Sinalização das MAP Quinases , Camundongos , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Neuritos/fisiologia , Plasticidade Neuronal , Neurônios/metabolismo , Neurônios/fisiologia , Fosforilação , Fosfotirosina/metabolismo , Proteínas Tirosina Quinases/metabolismo , Fator de Transcrição STAT3 , Transdução de Sinais , Transfecção , Quinases da Família srcRESUMO
A sample of lunar material from Apollo 11 was subjected to analysis by several techniques, which included mass spectrometry, gas chromatography, liquid chromatography, and nuclear magnetic resonance and their variations, in an effort to detect the presence of organic compounds. None were found. On the basis of the sensitivity ascribed to certain of the methods employed, it is assumed that if organic matter were present it would exist in concentrations less than 1 part per million. phere.
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Signal transducers and activators of transcription (STATs) enhance transcription of specific genes in response to cytokines and growth factors. STAT1 is also required for efficient constitutive expression of the caspases Ice, Cpp32, and Ich-1 in human fibroblasts. As a consequence, STAT1-null cells are resistant to apoptosis by tumor necrosis factor alpha (TNF-alpha). Reintroduction of STAT1alpha restored both TNF-alpha-induced apoptosis and the expression of Ice, Cpp32, and Ich-1. Variant STAT1 proteins carrying point mutations that inactivate domains required for STAT dimer formation nevertheless restored protease expression and sensitivity to apoptosis, indicating that the functions of STAT1 required for these activities are different from those that mediate induced gene expression.
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Apoptose , Caspases , Cisteína Endopeptidases/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas/metabolismo , Transativadores/metabolismo , Fator de Necrose Tumoral alfa/farmacologia , Caspase 1 , Caspase 2 , Caspase 3 , Linhagem Celular , Cisteína Endopeptidases/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Dactinomicina/farmacologia , Dimerização , Regulação Enzimológica da Expressão Gênica , Humanos , Interferon gama/farmacologia , Fosforilação , Mutação Puntual , Proteínas/genética , Fator de Transcrição STAT1 , Transdução de Sinais , Transativadores/química , Transativadores/genética , TransfecçãoRESUMO
Multitubular enzyme reactors with immobilized phenylalanine ammonia lyase were tested in vitro and in vivo for depletion of phenylalanine in circulating blood. Sustained reduction of phenylalanine was achieved in less than 30 minutes. A 50% decrease of phenylalanine was obtained with a 2-hour application of enzyme reactors and was maintained for more than 2 days. Similar enzyme reactors have therapeutic potential for temporary management of phenylketonuric patients when their circulating phenylalanine becomes exceedingly high because of infection, fever, or pregnancy.
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Amônia-Liases/uso terapêutico , Modelos Animais de Doenças , Enzimas Imobilizadas/uso terapêutico , Fenilalanina Amônia-Liase/uso terapêutico , Fenilcetonúrias/terapia , Animais , Cães , Circulação Extracorpórea , Humanos , Fenilalanina/sangueRESUMO
Signal transducer and activator of transcription (STAT) transcription factors are implicated in programming gene expression in biological events as diverse as embryonic development, programmed cell death, organogenesis, innate immunity, adaptive immunity and cell growth regulation in organisms ranging from slime molds to insects to man. Rapid progress has unearthed much about the activation of STATs by Janus kinases (JAKs) and other tyrosine kinases and their ability to interface with other signaling systems. Once inside the nucleus, the STATs bind to promoters and join other transcriptional activators in the regulation of gene expression.
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Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas do Leite , Transativadores/genética , Transativadores/metabolismo , Transcrição Gênica , Animais , Proteínas de Ligação a DNA/química , Matriz Extracelular/metabolismo , Humanos , Fator de Transcrição STAT1 , Fator de Transcrição STAT2 , Fator de Transcrição STAT3 , Fator de Transcrição STAT4 , Fator de Transcrição STAT5 , Fator de Transcrição STAT6 , Transdução de Sinais , Transativadores/química , Ativação TranscricionalRESUMO
Influenza viruses have exploited a variety of strategies to increase their genome coding capacities. These include unspliced, spliced, alternatively spliced and bicistronic mRNAs, translation from overlapping reading frames and a coupled stop-start translation of tandem cistrons.
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Regulação Viral da Expressão Gênica , Genes Virais , Orthomyxoviridae/genética , RNA Viral/genética , Sequência de Bases , Homologia de Genes , Dados de Sequência Molecular , Fases de Leitura Aberta , Biossíntese de Proteínas , Splicing de RNA , RNA Mensageiro/genética , Transcrição Gênica , Proteínas Virais/genéticaRESUMO
BACKGROUND: Human papillomavirus (HPV) plays a critical role in the carcinogenesis of squamous cervical carcinoma. Integration of viral DNA into the host genome is a major contributing factor to malignant transformation. Viral load may influence integration. AIMS: To compare HPV status (type, viral load, integration status) between normal samples, carcinoma in situ and invasive carcinoma in order to elucidate the role of HPV in progression to invasive lesions. METHODS: The study population comprised 10 biopsy samples from each diagnostic group. Laminin-5 immunohistochemistry was performed to distinguish invasive carcinoma from non-invasive high-grade lesions. Real-time PCR was used to detect specific HPV types, viral load and integrated HPV, with quantification of viral E2 and E6 genes. RESULTS: Invasive carcinomas contained a higher number of laminin-5 immunoreactive cells as compared to non-invasive lesions. Almost all samples contained HPV, with a higher viral load and copy number of HPV16 integrated in E2 in cases of laminin-5 immunoreactivity and cases of invasive carcinoma. High HPV16 viral load was associated with more integrated copies in E2. CONCLUSIONS: HPV is important in progression from carcinoma in situ to invasive carcinoma. Viral load and HPV integration influence the development of cervical cancer towards invasiveness. Overall HPV status may be more predictive of patient outcome and may influence patient management.
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Carcinoma de Células Escamosas/imunologia , Moléculas de Adesão Celular/imunologia , Infecções por Papillomavirus/genética , Neoplasias do Colo do Útero/imunologia , Carcinoma de Células Escamosas/complicações , Carcinoma de Células Escamosas/virologia , DNA Viral/genética , Progressão da Doença , Feminino , Genes Virais , Células HeLa , Papillomavirus Humano 6/genética , Humanos , Imuno-Histoquímica/métodos , Invasividade Neoplásica , Papillomaviridae/genética , Infecções por Papillomavirus/complicações , Infecções por Papillomavirus/imunologia , Neoplasias do Colo do Útero/complicações , Neoplasias do Colo do Útero/virologia , Carga Viral , Displasia do Colo do Útero/complicações , Displasia do Colo do Útero/imunologia , Displasia do Colo do Útero/virologia , CalininaRESUMO
Independent but closely spaced DNA binding sites for Stat3 and c-Jun are required for maximal enhancer function in a number of genes, including the gene encoding the interleukin-6 (IL-6)-induced acute-phase response protein, alpha(2)-macroglobulin. In addition, a physical interaction of Stat3 with c-Jun, based on yeast two-hybrid interaction experiments, has been reported. Here we confirm the existence of an interaction between Stat3 and c-Jun both in vitro, with recombinant proteins, and in vivo, during transient transfection. Using fragments of both proteins, we mapped the interactive sites to the C-terminal region of c-Jun and to two regions in Stat3, within the coiled-coil domain and in a portion of the DNA binding domain distant from DNA contact sites. In transient-transfection experiments with the alpha(2)-macroglobulin enhancer, Stat3 and c-Jun cooperated to yield maximal enhancer function. Point mutations of Stat3 within the interacting domains blocked both physical interaction of Stat3 with c-Jun and their cooperation in IL-6-induced transcription directed by the alpha(2)-macroglobulin enhancer. While the amino acid sequences and the three-dimensional structures of Stat3 and Stat1 cores are very similar, fragments of Stat1 failed to bind c-Jun in vitro. Although Stat1 binds in vitro to the gamma interferon gene response (GAS) element in the alpha(2)-macroglobulin enhancer, Stat1 did not stimulate transcription, nor did Stat1 and c-Jun cooperate in driving transcription controlled by the alpha(2)-macroglobulin enhancer.
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Proteínas de Ligação a DNA/metabolismo , Proteínas Proto-Oncogênicas c-jun/metabolismo , Transativadores/metabolismo , Ativação Transcricional , Sequência de Aminoácidos , Sítios de Ligação/genética , Proteínas de Ligação a DNA/genética , Humanos , Interleucina-6/farmacologia , Modelos Moleculares , Dados de Sequência Molecular , Ligação Proteica , Fator de Transcrição STAT3 , Transativadores/genética , alfa-Macroglobulinas/genéticaRESUMO
The first STAT-containing transcription factor to be studied, the alpha-interferon-induced ISGF3, is composed of a Stat1:2 heterodimer and a weak DNA-binding protein, p48, that is a member of a growing family of proteins similar to the so-called interferon regulatory factor (IRF-1). The p48 and Stat1:2 heterodimer do not associate stably in the absence of DNA, but we show that amino acids approximately 150 to 250 of Stat1 and a COOH-terminal portion of p48 exhibit physical interaction, implying contact that stabilizes ISGF3. Moreover, amino acid exchanges within the Stat1 contact region diminish or abolish the functional activity of Stat1. This protein interaction domain may be important in other STAT proteins to recruit partners to multiprotein transcription factors.
Assuntos
Proteínas de Ligação a DNA/genética , Transativadores/genética , Fatores de Transcrição/genética , Transcrição Gênica , Fator Gênico 3 Estimulado por Interferon , Fator Gênico 3 Estimulado por Interferon, Subunidade gama , Ligação Proteica/genética , Fator de Transcrição STAT1 , Fator de Transcrição STAT2RESUMO
Stat3 activation has been associated with cytokine-induced proliferation, anti-apoptosis, and transformation. Constitutively activated Stat3 has been found in many human tumors as well as v-abl- and v-src-transformed cell lines. Because of these correlations, we examined directly the relationship of activated Stat3 to cellular transformation and found that wild-type Stat3 enhances the transforming potential of v-src while three dominant negative Stat3 mutants inhibit v-src transformation. Stat3 wild-type or mutant proteins did not affect v-ras transformation. We conclude that Stat3 has a necessary role in v-src transformation.