RESUMEN
In the vertebrate lineage of the U1A/U2Bâ³/SNF protein family, the U1A and U2Bâ³ proteins bind to RNA stem-loops in the U1 or U2 snRNPs, respectively. However, their specialization is fairly recent, as they evolved from a single ancestral protein. The progress of their specialization (subfunctionalization) can be monitored by the amino acid sequence changes that give rise to their modern RNA-binding specificity. Using ancestral sequence reconstruction to predict the intermediates on the evolutionary branch, a probable path of sequential changes is defined for U1A and U2Bâ³. The RNA-binding affinity for U1A/U2Bâ³ protein ancestors was measured using modern U1 and U2 snRNA stem-loops and RNA stem-loop variants to understand how the proteins' RNA specificities evolved.
Asunto(s)
Evolución Molecular , Especiación Genética , Ribonucleoproteína Nuclear Pequeña U1/genética , Ribonucleoproteína Nuclear Pequeña U2/genética , Vertebrados/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Filogenia , Ribonucleoproteína Nuclear Pequeña U1/química , Ribonucleoproteína Nuclear Pequeña U2/química , Homología de Secuencia de Aminoácido , Vertebrados/clasificación , Proteínas Nucleares snRNP/química , Proteínas Nucleares snRNP/genéticaRESUMEN
The U1A and U2Bâ³ proteins are components of the U1 and U2 snRNPs, respectively, where they bind to snRNA stemloops. While localization of U1A and U2Bâ³ to their respective snRNP is a well-known phenomenon, binding of U2Bâ³ to U2 snRNA is typically thought to be accompanied by the U2A' protein. The molecular mechanisms that lead to formation of the RNA/U2Bâ³/U2A' complex and its localization to the U2 snRNP are investigated here, using a combination of in vitro RNA-protein and protein-protein fluorescence and isothermal titration calorimetry binding experiments. We find that U2A' protein binds to U2Bâ³ with nanomolar affinity but binds to U1A with only micromolar affinity. In addition, there is RNA-dependent cooperativity (linkage) between protein-protein and protein-RNA binding. The unique combination of tight binding and cooperativity ensures that the U2A'/U2Bâ³ complex is partitioned only to the U2 snRNP.
Asunto(s)
Modelos Moleculares , ARN Nuclear Pequeño/metabolismo , Ribonucleoproteína Nuclear Pequeña U2/metabolismo , Proteínas Nucleares snRNP/metabolismo , Secuencia de Aminoácidos , Humanos , Datos de Secuencia Molecular , Motivos de Nucleótidos , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/metabolismo , Dominios y Motivos de Interacción de Proteínas , Multimerización de Proteína , Estabilidad Proteica , Estabilidad del ARN , ARN Nuclear Pequeño/química , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Ribonucleoproteína Nuclear Pequeña U1/química , Ribonucleoproteína Nuclear Pequeña U1/genética , Ribonucleoproteína Nuclear Pequeña U1/metabolismo , Ribonucleoproteína Nuclear Pequeña U2/química , Ribonucleoproteína Nuclear Pequeña U2/genética , Alineación de Secuencia , Termodinámica , Proteínas Nucleares snRNP/química , Proteínas Nucleares snRNP/genéticaRESUMEN
Drosophila SNF is a member of the U1A/U2Bâ³/SNF protein family that is found in U1 and U2 snRNPs, where it binds to Stemloop II and Stemloop IV of U1 and U2 snRNA, respectively. SNF also binds to the U2A' protein, but only in the U2 snRNP. Although previous reports have implicated U2A' as a necessary auxiliary protein for the binding of SNF to Stemloop IV, there are no mechanisms that explain the partitioning of U2A' to the U2 snRNP and its absence from the U1 snRNP. Using in vitro RNA binding isotherms and isothermal titration calorimetry, the thermodynamics of SNF/RNA/U2A' ternary complex formation have now been characterized. There is a very large binding cooperativity unique to Stemloop IV that favors formation of the SLIV/SNF/U2A' complex. The binding cooperativity, or heterotropic linkage, is interpreted with respect to linked conformational equilibria of both SNF and its RNA ligand and so represents an example of protein-RNA allostery.
Asunto(s)
Proteínas de Drosophila/química , Proteínas de Drosophila/metabolismo , ARN/química , ARN/metabolismo , Ribonucleoproteína Nuclear Pequeña U2/química , Ribonucleoproteína Nuclear Pequeña U2/metabolismo , Regulación Alostérica , Animales , Drosophila , Humanos , Unión Proteica/fisiología , Ribonucleoproteína Nuclear Pequeña U1RESUMEN
Although autoimmunity and autoimmune disease (AID) are relatively common, the repertoire of autoantigens is paradoxically very limited. Highly enriched in this autoantigen repertoire are nucleic acids and their binding proteins, which together form large macromolecular structures. Most of these complexes are of ancient evolutionary origin, with homologs throughout multiple kingdoms of life. Why and if these nucleic acid-protein particles drive the development of autoimmunity remains unresolved. Recent advances in our understanding of the microbiome may provide clues about the origins of autoimmunity - and the particular puzzle of why the autoantigen repertoire is so particularly enriched in ribonucleoprotein particles (RNPs). We discuss the possibility that autoimmunity to some RNPs may arise from molecular mimicry to microbial orthologs.
Asunto(s)
Autoantígenos , Autoinmunidad , Microbiota , Ribonucleoproteínas/genética , Autoantígenos/genética , Autoantígenos/inmunología , Enfermedades Autoinmunes , Autoinmunidad/genética , Autoinmunidad/inmunología , Genes Bacterianos , Humanos , Inmunidad , Microbiota/genética , Microbiota/inmunología , Imitación MolecularRESUMEN
OBJECTIVE: Latino patients are overrepresented among cases of coronavirus disease 2019 (COVID-19) and are at an increased risk of severe disease. Prevalence of COVID-19 in Latinos with rheumatic diseases is poorly reported. This study was undertaken to characterize COVID-19 clinical features and outcomes in Latino patients with rheumatic diseases. METHODS: We conducted a retrospective study of Latino patients with rheumatic diseases from an existing observational cohort in the Washington, DC area. Patients seen between April 1, 2020 and October 15, 2020 were analyzed in this study. We reviewed demographic characteristics, body mass index (BMI), comorbidities, and use of immunomodulatory therapies. An exploratory classification and regression tree (CART) analysis along with logistic regression analyses were performed to identify risk factors for COVID-19 and rheumatic disease flare. RESULTS: Of 178 Latino patients with rheumatic diseases, 32 (18%) were identified as having COVID-19, and the incidence rate of infection was found to be 3-fold higher than in the general Latino population. No patients required intensive care unit-level care. A CART analysis and multivariable logistic regression analysis identified a BMI of >30.35 as a risk factor for COVID-19 (odds ratio [OR] 3.37 [95% confidence interval (95% CI) 1.5-7.7]; P = 0.004). COVID-19 positivity was a risk factor for rheumatic disease flare (OR 4.57 [95% CI 1.2-17.4]; P = 0.02). CONCLUSION: Our findings indicate that Latino patients with rheumatic diseases have a higher rate of COVID-19 compared with the general Latino population. Obesity is a risk factor for COVID-19, and COVID-19 is a risk factor for rheumatic disease flare. Latino patients with risk factors should be closely followed up, especially post-COVID-19 in anticipation of disease flare.
Asunto(s)
COVID-19/diagnóstico , Enfermedades Reumáticas/epidemiología , Adulto , COVID-19/epidemiología , Estudios de Cohortes , Comorbilidad , Femenino , Hispánicos o Latinos , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Factores de Riesgo , Índice de Severidad de la Enfermedad , Estados UnidosRESUMEN
SNF is a protein that is found in the U1 and U2 snRNPs (small nuclear ribonucleoproteins) of Drosophila. Its mammalian counterparts are two homologous proteins, U1A and U2B''. In vivo, these proteins segregate to the U1 and U2 snRNPs, respectively, where they bind distinct RNA hairpins. The RNA binding properties and mechanism of U1A have been studied extensively, but much less is known about SNF and U2B'' binding to their RNA targets. By comparing thermodynamic aspects of SNF-RNA interactions with those of U1A-RNA interactions, we find that SNF binds its RNA targets in a manner that is distinct from that of U1A. In vitro, SNF is able to bind both Drosophila U1 stem-loop II and U2 stem-loop IV with high affinity, although it binds stem-loop II more tightly than it binds stem-loop IV. Intriguingly, SNF is unable to bind human U2 stem-loop IV, which suggests that both the protein and RNAs have coevolved to interact with each other such that a single protein can bind RNAs that are more commonly bound by two distinct proteins.
Asunto(s)
Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Evolución Molecular , Marcación de Gen , ARN Nuclear Pequeño/química , ARN Nuclear Pequeño/metabolismo , Ribonucleoproteína Nuclear Pequeña U1/química , Ribonucleoproteína Nuclear Pequeña U1/genética , Secuencias de Aminoácidos/genética , Secuencia de Aminoácidos , Animales , Proteínas de Drosophila/metabolismo , Humanos , Datos de Secuencia Molecular , Unión Proteica/genética , Pliegue de Proteína , Estructura Terciaria de Proteína/genética , ARN Nuclear Pequeño/genética , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Ribonucleoproteína Nuclear Pequeña U1/metabolismo , TermodinámicaRESUMEN
INTRODUCTION: Immune checkpoint inhibitors (ICIs) have proved to be groundbreaking in the field of oncology. However, immune system overactivation from ICIs has introduced a novel medical entity known as immune-related adverse events (irAEs), that can affect any organ or tissue. ICI-induced inflammatory arthritis (ICI-IIA) is the most common musculoskeletal irAE and can lead to significant morbidity and limitation in anti-cancer therapy. AREAS COVERED: In this review, the authors focus on ICI-IIA. Relevant articles were identified through PubMed searches, spanning 2010 to the present. The authors detail the current understanding of its pathogenesis, diagnostic evaluation, and management strategies. EXPERT OPINION: ICI-IIA is a complex irAE that we are just beginning to understand mechanistically and pathologically. It often presents later in the disease course than other irAEs and, due to various reasons, is under-recognized. In some patients, ICI-IIA may become a chronic disease, which distinguishes it from most irAEs that resolve after ICI discontinuation. Multiple important questions still demand further research including which patients may develop ICI-IIA? What are possible diagnostic and prognostic markers? Do anti-arthritis therapies interfere with the anti-tumor response? and when should steroid-sparing agents be initiated? Close collaboration and shared decision-making between oncologists, rheumatologists, and the patient are essential when managing this particular irAE.
Asunto(s)
Artritis/inducido químicamente , Inhibidores de Puntos de Control Inmunológico/efectos adversos , Artritis/diagnóstico , Artritis/epidemiología , Artritis/terapia , Enfermedades Autoinmunes/complicaciones , Humanos , Inhibidores de Puntos de Control Inmunológico/farmacologíaRESUMEN
PURPOSE: To characterize rheumatological manifestations of GATA2 deficiency. METHODS: Single-center, retrospective review of 157 patients with GATA2 deficiency. Disease course, laboratory results, and imaging findings were extracted. In-person rheumatological assessments were performed on selected, available patients. A literature search of four databases was conducted to identify additional cases. RESULTS: Rheumatological findings were identified in 28 patients, out of 157 cases reviewed (17.8%). Twenty-two of those patients (78.6%) reported symptom onset prior to or in conjunction with the molecular diagnosis of GATA2 deficiency. Notable rheumatological manifestations included: piezogenic pedal papules (PPP), joint hyperextensibility, early onset osteoarthritis, ankylosing spondylitis, and seronegative erosive rheumatoid arthritis. In peripheral blood of patients with rheumatological manifestations and GATA2 deficiency, CD4+ CD3+ helper T cells and naïve CD3+ CD4+ CD62L+ CD45RA+ helper T cell subpopulation fractions were significantly lower, while CD8+ cytotoxic T cell fractions were significantly higher, compared to those without rheumatological manifestations and with GATA2 deficiency. No changes in CD19, CD3, or NK populations were observed. CONCLUSION: GATA2 deficiency is associated with a broad spectrum of rheumatological disease manifestations. Low total helper T lymphocyte proportions and low naïve helper T cell proportions are associated with those most at risk of overt rheumatological manifestations. Further, PPP and joint hyperextensibility may explain some of the nonimmunologically-mediated joint problems encountered in patients with GATA2 deficiency. This catalogue suggests that rheumatological manifestations and immune dysregulation are relatively common in GATA2 deficiency.
Asunto(s)
Deficiencia GATA2/complicaciones , Enfermedades Reumáticas/etiología , Femenino , Deficiencia GATA2/inmunología , Humanos , Enfermedades del Sistema Inmune/etiología , Masculino , Estudios RetrospectivosRESUMEN
Importance: Immune checkpoint inhibitors (ICIs) have transformed the treatment paradigm for an ever-increasing number of cancers. However, their use has also led to the emergence of immune-related adverse events, such as ICI-induced inflammatory arthritis. A reproducible, reliable, and accessible modality is needed to assess and distinguish early ICI-induced inflammatory arthritis and help in management. Magnetic resonance imaging (MRI) of joints may be helpful for early diagnosis, guiding therapeutic decision-making, and identifying patients at high risk for erosive disease. Objective: To assess the role of MRI of joints in patients with ICI-induced inflammatory arthritis. Design, Setting, and Participants: This retrospective case series included patients enrolled at the National Institutes of Health Clinical Center in Bethesda, Maryland. Patients were evaluated by the rheumatology consultation service between December 27, 2016, and May 28, 2019. A retrospective health record review was performed to determine demographic characteristics, clinical characteristics of inflammatory arthritis and malignant tumors, and imaging findings. Inclusion criteria were patients who were enrolled on various institutional review board-approved protocols of ICIs, developed joint-related symptoms, and had MRI data for at least 1 joint. Data were analyzed from June 1, 2019, to September 1, 2019. Exposures: Undergoing MRI of at least 1 joint. Main Outcomes and Measures: All MRIs were reviewed for synovitis, tenosynovitis, bone marrow edema, and soft tissue conditions. Results: A total of 8 patients (mean [SD] age, 58.8 [5.2] years; 6 women and 2 men) between the ages of 50 and 65 years who were undergoing ICI therapy for a variety of malignant tumors were included in this study. Only 1 patient was receiving combined ICI therapy. The results of 13 separate MRI examinations were reviewed. The most commonly performed MRIs were of the hands and wrists (9 MRIs), followed by knee examinations (3 MRIs). Tenosynovitis and synovitis were frequently seen in the hands and wrists. Bone marrow edema and erosions were also found in 3 patients, suggesting early damage. In larger joints (ie, knees and ankles), joint effusions and synovial thickening were characteristic. Most patients (5 patients) were treated with corticosteroids and had good responses. In patients with high-risk features on MRI imaging (eg, bone marrow edema, erosions), disease-modifying antirheumatic drug therapy was also discussed as a treatment option. Conclusions and Relevance: These findings suggest that advanced imaging may help to distinguish ICI-induced inflammatory arthritis from other causes of joint pain, aid in identifying patients at increased risk of joint damage, and provide utility in monitoring inflammatory arthritis treatment response in patients receiving ICI therapy.
Asunto(s)
Antineoplásicos Inmunológicos/efectos adversos , Artritis Reumatoide/diagnóstico , Inmunoterapia/efectos adversos , Articulaciones/diagnóstico por imagen , Neoplasias/tratamiento farmacológico , Anciano , Artritis Reumatoide/inducido químicamente , Diagnóstico Precoz , Femenino , Humanos , Articulaciones/patología , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Estudios RetrospectivosRESUMEN
The U1A/U2Bâ³/SNF family of proteins found in the U1 and U2 spliceosomal small nuclear ribonucleoproteins is highly conserved. In spite of the high degree of sequence and structural conservation, modern members of this protein family have unique RNA binding properties. These differences have necessarily resulted from evolutionary processes, and therefore, we reconstructed the protein phylogeny in order to understand how and when divergence occurred and how protein function has been modulated. Contrary to the conventional understanding of an ancient human U1A/U2Bâ³ gene duplication, we show that the last common ancestor of bilaterians contained a single ancestral protein (URB). The gene for URB was synthesized, the protein was overexpressed and purified, and we assessed RNA binding to modern snRNA sequences. We find that URB binds human and Drosophila U1 snRNA SLII and U2 snRNA SLIV with higher affinity than do modern homologs, suggesting that both Drosophila SNF and human U1A/U2Bâ³ have evolved into weaker binders of one RNA or both RNAs.
Asunto(s)
Ribonucleoproteína Nuclear Pequeña U1/metabolismo , Proteínas Nucleares snRNP/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Drosophila , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Evolución Molecular , Duplicación de Gen , Humanos , Secuencias Invertidas Repetidas , Modelos Moleculares , Datos de Secuencia Molecular , Conformación de Ácido Nucleico , Filogenia , Unión Proteica , Conformación Proteica , ARN Nuclear Pequeño/química , ARN Nuclear Pequeño/genética , ARN Nuclear Pequeño/metabolismo , Ribonucleoproteína Nuclear Pequeña U1/química , Ribonucleoproteína Nuclear Pequeña U1/genética , Ribonucleoproteínas Nucleares Pequeñas/química , Ribonucleoproteínas Nucleares Pequeñas/genética , Ribonucleoproteínas Nucleares Pequeñas/metabolismo , Alineación de Secuencia , Empalmosomas/metabolismo , Proteínas Nucleares snRNP/química , Proteínas Nucleares snRNP/genéticaRESUMEN
The human U2Bâ³ protein is one of the unique proteins that comprise the U2 snRNP, but it is also a representative of the U1A/U2Bâ³ protein family. In the U2 snRNP, it is bound to Stem-Loop IV (SLIV) of the U2 snRNA. We find that in vitro it binds not only to human SLIV, but also to Stem-Loop II (SLII) from human U1 snRNA and to Drosophila U2 snRNA SLIV. The thermodynamics of these binding interactions show a striking similarity, leading to the conclusion that U2Bâ³ has a relaxed specificity for its RNA targets. The binding properties of U2Bâ³ are distinct from those of human U1A and of Drosophila SNF, despite its high homology to those proteins, and so provide important new information on how this protein family has modulated its target preferences.