RESUMEN
Ten-eleven translocation (TET) proteins are iron-dependent and α-ketoglutarate-dependent dioxygenases that sequentially oxidize the methyl group of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). All three epigenetic modifications are intermediates in DNA demethylation. TET proteins are recruited by transcription factors and by RNA polymerase II to modify 5mC at enhancers and gene bodies, thereby regulating gene expression during development, cell lineage specification, and cell activation. It is not yet clear, however, how the established biochemical activities of TET enzymes in oxidizing 5mC and mediating DNA demethylation relate to the known association of TET deficiency with inflammation, clonal hematopoiesis, and cancer. There are hints that the ability of TET deficiency to promote cell proliferation in a signal-dependent manner may be harnessed for cancer immunotherapy. In this review, we draw upon recent findings in cells of the immune system to illustrate established as well as emerging ideas of how TET proteins influence cellular function.
Asunto(s)
Desmetilación del ADN , Dioxigenasas , Inmunoterapia , Inflamación , Neoplasias , Humanos , Neoplasias/terapia , Neoplasias/inmunología , Neoplasias/etiología , Neoplasias/metabolismo , Animales , Inflamación/metabolismo , Inflamación/inmunología , Inmunoterapia/métodos , Dioxigenasas/metabolismo , Sistema Inmunológico/metabolismo , Sistema Inmunológico/inmunología , Epigénesis Genética , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas/genética , Metilación de ADN , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Oxigenasas de Función Mixta/metabolismo , Oxigenasas de Función Mixta/genéticaRESUMEN
A fundamental question in developmental immunology is how bipotential thymocyte precursors generate both CD4+ helper and CD8+ cytotoxic T cell lineages. The MHC specificity of αß T cell receptors (TCRs) on precursors is closely correlated with cell fate-determining processes, prompting studies to characterize how variations in TCR signaling are linked with genetic programs establishing lineage-specific gene expression signatures, such as exclusive CD4 or CD8 expression. The key transcription factors ThPOK and Runx3 have been identified as mediating development of helper and cytotoxic T cell lineages, respectively. Together with increasing knowledge of epigenetic regulators, these findings have advanced our understanding of the transcription factor network regulating the CD4/CD8 dichotomy. It has also become apparent that CD4+ T cells retain developmental plasticity, allowing them to acquire cytotoxic activity in the periphery. Despite such advances, further studies are necessary to identify the molecular links between TCR signaling and the nuclear machinery regulating expression of ThPOK and Runx3.
Asunto(s)
Diferenciación Celular/inmunología , Linfocitos T Citotóxicos/citología , Linfocitos T Citotóxicos/inmunología , Linfocitos T Colaboradores-Inductores/citología , Linfocitos T Colaboradores-Inductores/inmunología , Animales , Antígenos CD4/genética , Antígenos CD4/metabolismo , Antígenos CD8/genética , Antígenos CD8/metabolismo , Diferenciación Celular/genética , Linaje de la Célula/genética , Linaje de la Célula/inmunología , Subunidad alfa 3 del Factor de Unión al Sitio Principal/genética , Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica , Humanos , Inmunomodulación/genética , Inmunomodulación/inmunología , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/metabolismo , Secuencias Reguladoras de Ácidos Nucleicos , Linfocitos T Citotóxicos/metabolismo , Linfocitos T Colaboradores-Inductores/metabolismo , Factores de Transcripción/genética , Transcripción GenéticaRESUMEN
Covalent DNA-protein crosslinks (DPCs) are pervasive DNA lesions that interfere with essential chromatin processes such as transcription or replication. This review strives to provide an overview of the sources and principles of cellular DPC formation. DPCs are caused by endogenous reactive metabolites and various chemotherapeutic agents. However, in certain conditions DPCs also arise physiologically in cells. We discuss the cellular mechanisms resolving these threats to genomic integrity. Detection and repair of DPCs require not only the action of canonical DNA repair pathways but also the activity of specialized proteolytic enzymes-including proteases of the SPRTN/Wss1 family-to degrade the crosslinked protein. Loss of DPC repair capacity has dramatic consequences, ranging from genome instability in yeast and worms to cancer predisposition and premature aging in mice and humans.
Asunto(s)
Reparación del ADN , Proteínas de Saccharomyces cerevisiae , Animales , ADN/genética , ADN/metabolismo , Daño del ADN , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Inestabilidad Genómica , Ratones , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMEN
In eukaryotes, transcription of protein-coding genes requires the assembly at core promoters of a large preinitiation machinery containing RNA polymerase II (RNAPII) and general transcription factors (GTFs). Transcription is potentiated by regulatory elements called enhancers, which are recognized by specific DNA-binding transcription factors that recruit cofactors and convey, following chromatin remodeling, the activating cues to the preinitiation complex. This review summarizes nearly five decades of work on transcription initiation by describing the sequential recruitment of diverse molecular players including the GTFs, the Mediator complex, and DNA repair factors that support RNAPII to enable RNA synthesis. The elucidation of the transcription initiation mechanism has greatly benefited from the study of altered transcription components associated with human diseases that could be considered transcription syndromes.
Asunto(s)
ARN Polimerasa II/metabolismo , Secuencias Reguladoras de Ácidos Nucleicos , Factor de Transcripción TFIID/genética , Factor de Transcripción TFIIH/genética , Iniciación de la Transcripción Genética/fisiología , Reparación del ADN/fisiología , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Humanos , Complejo Mediador/genética , Complejo Mediador/metabolismo , Mutación , Regiones Promotoras Genéticas , ARN Polimerasa II/genética , SíndromeRESUMEN
Facultative heterochromatin (fHC) concerns the developmentally regulated heterochromatinization of different regions of the genome and, in the case of the mammalian X chromosome and imprinted loci, of only one allele of a homologous pair. The formation of fHC participates in the timely repression of genes, by resisting strong trans activators. In this review, we discuss the molecular mechanisms underlying the establishment and maintenance of fHC in mammals using a mouse model. We focus on X-chromosome inactivation (XCI) as a paradigm for fHC but also relate it to genomic imprinting and homeobox (Hox) gene cluster repression. A vital role for noncoding transcription and/or transcripts emerges as the general principle of triggering XCI and canonical imprinting. However, other types of fHC are established through an unknown mechanism, independent of noncoding transcription (Hox clusters and noncanonical imprinting). We also extensively discuss polycomb-group repressive complexes (PRCs), which frequently play a vital role in fHC maintenance.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Impresión Genómica , Heterocromatina/metabolismo , Proteínas del Grupo Polycomb/genética , Inactivación del Cromosoma X , Cromosoma X/metabolismo , Animales , Ensamble y Desensamble de Cromatina , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Embrión de Mamíferos , Femenino , Silenciador del Gen , Heterocromatina/química , Histona Desacetilasas/genética , Histona Desacetilasas/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Masculino , Oocitos/citología , Oocitos/crecimiento & desarrollo , Oocitos/metabolismo , Proteínas del Grupo Polycomb/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Espermatozoides/citología , Espermatozoides/crecimiento & desarrollo , Espermatozoides/metabolismo , Cromosoma X/químicaRESUMEN
Homologous recombination (HR) helps maintain genome integrity, and HR defects give rise to disease, especially cancer. During HR, damaged DNA must be aligned with an undamaged template through a process referred to as the homology search. Despite decades of study, key aspects of this search remain undefined. Here, we use single-molecule imaging to demonstrate that Rad54, a conserved Snf2-like protein found in all eukaryotes, switches the search from the diffusion-based pathways characteristic of the basal HR machinery to an active process in which DNA sequences are aligned via an ATP-dependent molecular motor-driven mechanism. We further demonstrate that Rad54 disrupts the donor template strands, enabling the search to take place within a migrating DNA bubble-like structure that is bound by replication protein A (RPA). Our results reveal that Rad54, working together with RPA, fundamentally alters how DNA sequences are aligned during HR.
Asunto(s)
Adenosina Trifosfato/genética , ADN Helicasas/genética , Enzimas Reparadoras del ADN/genética , ADN/genética , Recombinación Homóloga/genética , Proteínas de Saccharomyces cerevisiae/genética , Adenosina Trifosfatasas/genética , Daño del ADN/genética , Reparación del ADN/genética , Proteínas de Unión al ADN/genética , Hidrólisis , Saccharomyces cerevisiae/genética , Alineación de Secuencia/métodosRESUMEN
The three-dimensional structures of chromosomes are increasingly being recognized as playing a major role in cellular regulatory states. The efficiency and promiscuity of phage Mu transposition was exploited to directly measure in vivo interactions between genomic loci in E. coli. Two global organizing principles have emerged: first, the chromosome is well-mixed and uncompartmentalized, with transpositions occurring freely between all measured loci; second, several gene families/regions show "clustering": strong three-dimensional co-localization regardless of linear genomic distance. The activities of the SMC/condensin protein MukB and nucleoid-compacting protein subunit HU-α are essential for the well-mixed state; HU-α is also needed for clustering of 6/7 ribosomal RNA-encoding loci. The data are explained by a model in which the chromosomal structure is driven by dynamic competition between DNA replication and chromosomal relaxation, providing a foundation for determining how region-specific properties contribute to both chromosomal structure and gene regulation.
Asunto(s)
Bacteriófago mu/genética , Cromosomas Bacterianos/genética , Elementos Transponibles de ADN , Proteínas Cromosómicas no Histona/genética , Proteínas Cromosómicas no Histona/metabolismo , Cromosomas Bacterianos/química , ADN Bacteriano/química , ADN Bacteriano/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Escherichia coli , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Genoma Bacteriano , Conformación de Ácido Nucleico , Transposasas/genética , Transposasas/metabolismoRESUMEN
Inflammatory bowel disease (IBD) is a chronic inflammatory disease associated with increased risk of gastrointestinal cancers. We whole-genome sequenced 446 colonic crypts from 46 IBD patients and compared these to 412 crypts from 41 non-IBD controls from our previous publication on the mutation landscape of the normal colon. The average mutation rate of affected colonic epithelial cells is 2.4-fold that of healthy colon, and this increase is mostly driven by acceleration of mutational processes ubiquitously observed in normal colon. In contrast to the normal colon, where clonal expansions outside the confines of the crypt are rare, we observed widespread millimeter-scale clonal expansions. We discovered non-synonymous mutations in ARID1A, FBXW7, PIGR, ZC3H12A, and genes in the interleukin 17 and Toll-like receptor pathways, under positive selection in IBD. These results suggest distinct selection mechanisms in the colitis-affected colon and that somatic mutations potentially play a causal role in IBD pathogenesis.
Asunto(s)
Evolución Clonal/genética , Colitis/genética , Enfermedades Inflamatorias del Intestino/genética , Tasa de Mutación , Adulto , Anciano , Anciano de 80 o más Años , Envejecimiento/genética , Evolución Clonal/inmunología , Colitis/metabolismo , Colitis Ulcerosa/genética , Colitis Ulcerosa/metabolismo , Enfermedad de Crohn/genética , Enfermedad de Crohn/metabolismo , Proteínas de Unión al ADN/genética , Células Epiteliales/metabolismo , Células Epiteliales/patología , Proteína 7 que Contiene Repeticiones F-Box-WD/genética , Femenino , Humanos , Mutación INDEL , Enfermedades Inflamatorias del Intestino/inmunología , Enfermedades Inflamatorias del Intestino/metabolismo , Enfermedades Inflamatorias del Intestino/patología , Interleucina-17/metabolismo , Mucosa Intestinal/metabolismo , Mucosa Intestinal/patología , Masculino , Persona de Mediana Edad , Filogenia , Mutación Puntual , Receptores de Superficie Celular/genética , Ribonucleasas/genética , Receptores Toll-Like/genética , Factores de Transcripción/genética , Secuenciación Completa del GenomaRESUMEN
Metabolic reprogramming is a key feature of many cancers, but how and when it contributes to tumorigenesis remains unclear. Here we demonstrate that metabolic reprogramming induced by mitochondrial fusion can be rate-limiting for immortalization of tumor-initiating cells (TICs) and trigger their irreversible dedication to tumorigenesis. Using single-cell transcriptomics, we find that Drosophila brain tumors contain a rapidly dividing stem cell population defined by upregulation of oxidative phosphorylation (OxPhos). We combine targeted metabolomics and in vivo genetic screening to demonstrate that OxPhos is required for tumor cell immortalization but dispensable in neural stem cells (NSCs) giving rise to tumors. Employing an in vivo NADH/NAD+ sensor, we show that NSCs precisely increase OxPhos during immortalization. Blocking OxPhos or mitochondrial fusion stalls TICs in quiescence and prevents tumorigenesis through impaired NAD+ regeneration. Our work establishes a unique connection between cellular metabolism and immortalization of tumor-initiating cells.
Asunto(s)
Neoplasias Encefálicas/metabolismo , Carcinogénesis/metabolismo , Transformación Celular Neoplásica/metabolismo , Dinámicas Mitocondriales , NAD/metabolismo , Células Madre Neoplásicas/metabolismo , Células-Madre Neurales/metabolismo , Fosforilación Oxidativa , Animales , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/mortalidad , Neoplasias Encefálicas/patología , Carcinogénesis/genética , Carcinogénesis/patología , Transformación Celular Neoplásica/patología , Ciclo del Ácido Cítrico/genética , Biología Computacional , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Drosophila , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Glucólisis/genética , Espectrometría de Masas , Metabolómica , Microscopía Electrónica de Transmisión , Familia de Multigenes , Células-Madre Neurales/patología , Consumo de Oxígeno/genética , Interferencia de ARN , Especies Reactivas de Oxígeno/metabolismo , Análisis de la Célula Individual , Transcriptoma/genéticaRESUMEN
The recombination-activating genes (RAG) 1 and 2 are indispensable for diversifying the primary B cell receptor repertoire and pruning self-reactive clones via receptor editing in the bone marrow; however, the impact of RAG1/RAG2 on peripheral tolerance is unknown. Partial RAG deficiency (pRD) manifesting with late-onset immune dysregulation represents an 'experiment of nature' to explore this conundrum. By studying B cell development and subset-specific repertoires in pRD, we demonstrate that reduced RAG activity impinges on peripheral tolerance through the generation of a restricted primary B cell repertoire, persistent antigenic stimulation and an inflammatory milieu with elevated B cell-activating factor. This unique environment gradually provokes profound B cell dysregulation with widespread activation, remarkable extrafollicular maturation and persistence, expansion and somatic diversification of self-reactive clones. Through the model of pRD, we reveal a RAG-dependent 'domino effect' that impacts stringency of tolerance and B cell fate in the periphery.
Asunto(s)
Linfocitos B , Proteínas de Unión al ADN , Proteínas de Homeodominio , Proteínas Nucleares , Diferenciación Celular , Proteínas de Unión al ADN/deficiencia , Proteínas de Unión al ADN/genética , Proteínas de Homeodominio/genética , Humanos , Tolerancia Inmunológica , Recuento de Linfocitos , Proteínas Nucleares/deficienciaRESUMEN
Abasic sites are one of the most common DNA lesions. All known abasic site repair mechanisms operate only when the damage is in double-stranded DNA. Here, we report the discovery of 5-hydroxymethylcytosine (5hmC) binding, ESC-specific (HMCES) as a sensor of abasic sites in single-stranded DNA. HMCES acts at replication forks, binds PCNA and single-stranded DNA, and generates a DNA-protein crosslink to shield abasic sites from error-prone processing. This unusual HMCES DNA-protein crosslink intermediate is resolved by proteasome-mediated degradation. Acting as a suicide enzyme, HMCES prevents translesion DNA synthesis and the action of endonucleases that would otherwise generate mutations and double-strand breaks. HMCES is evolutionarily conserved in all domains of life, and its biochemical properties are shared with its E. coli ortholog. Thus, HMCES is an ancient DNA lesion recognition protein that preserves genome integrity by promoting error-free repair of abasic sites in single-stranded DNA.
Asunto(s)
5-Metilcitosina/análogos & derivados , Reparación del ADN/fisiología , ADN de Cadena Simple/fisiología , 5-Metilcitosina/metabolismo , Ácido Apurínico/metabolismo , ADN/metabolismo , Daño del ADN/fisiología , Replicación del ADN/fisiología , ADN de Cadena Simple/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Endonucleasas , Escherichia coli/metabolismo , Polinucleótidos/metabolismo , Antígeno Nuclear de Célula en Proliferación/metabolismoRESUMEN
Expansion of CAG trinucleotide repeats in ATXN1 causes spinocerebellar ataxia type 1 (SCA1), a neurodegenerative disease that impairs coordination and cognition. While ATXN1 is associated with increased Alzheimer's disease (AD) risk, CAG repeat number in AD patients is not changed. Here, we investigated the consequences of ataxin-1 loss of function and discovered that knockout of Atxn1 reduced CIC-ETV4/5-mediated inhibition of Bace1 transcription, leading to increased BACE1 levels and enhanced amyloidogenic cleavage of APP, selectively in AD-vulnerable brain regions. Elevated BACE1 expression exacerbated Aß deposition and gliosis in AD mouse models and impaired hippocampal neurogenesis and olfactory axonal targeting. In SCA1 mice, polyglutamine-expanded mutant ataxin-1 led to the increase of BACE1 post-transcriptionally, both in cerebrum and cerebellum, and caused axonal-targeting deficit and neurodegeneration in the hippocampal CA2 region. These findings suggest that loss of ataxin-1 elevates BACE1 expression and Aß pathology, rendering it a potential contributor to AD risk and pathogenesis.
Asunto(s)
Enfermedad de Alzheimer/patología , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Ataxina-1/metabolismo , Encéfalo/metabolismo , Enfermedad de Alzheimer/metabolismo , Secretasas de la Proteína Precursora del Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Ataxina-1/deficiencia , Ataxina-1/genética , Encéfalo/patología , Región CA2 Hipocampal/metabolismo , Región CA2 Hipocampal/patología , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Modelos Animales de Enfermedad , Femenino , Frecuencia de los Genes , Humanos , Masculino , Ratones , Ratones Transgénicos , Neurogénesis , Proteínas Proto-Oncogénicas c-ets/genética , Proteínas Proto-Oncogénicas c-ets/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción Genética , Repeticiones de Trinucleótidos/genética , Regulación hacia ArribaRESUMEN
Normal tissues accumulate genetic changes with age, but it is unknown if somatic mutations promote clonal expansion of non-malignant cells in the setting of chronic degenerative diseases. Exome sequencing of diseased liver samples from 82 patients revealed a complex mutational landscape in cirrhosis. Additional ultra-deep sequencing identified recurrent mutations in PKD1, PPARGC1B, KMT2D, and ARID1A. The number and size of mutant clones increased as a function of fibrosis stage and tissue damage. To interrogate the functional impact of mutated genes, a pooled in vivo CRISPR screening approach was established. In agreement with sequencing results, examination of 147 genes again revealed that loss of Pkd1, Kmt2d, and Arid1a promoted clonal expansion. Conditional heterozygous deletion of these genes in mice was also hepatoprotective in injury assays. Pre-malignant somatic alterations are often viewed through the lens of cancer, but we show that mutations can promote regeneration, likely independent of carcinogenesis.
Asunto(s)
Hepatopatías/patología , Hígado/metabolismo , Regeneración , Animales , Enfermedad Crónica , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Femenino , Humanos , Hidrolasas/deficiencia , Hidrolasas/genética , Hígado/patología , Cirrosis Hepática/inducido químicamente , Cirrosis Hepática/genética , Cirrosis Hepática/patología , Hepatopatías/genética , Masculino , Ratones , Ratones Noqueados , Persona de Mediana Edad , Mutación , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Regeneración/fisiología , Canales Catiónicos TRPP/genética , Canales Catiónicos TRPP/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Secuenciación del ExomaRESUMEN
The proteasome mediates selective protein degradation and is dynamically regulated in response to proteotoxic challenges. SKN-1A/Nrf1, an endoplasmic reticulum (ER)-associated transcription factor that undergoes N-linked glycosylation, serves as a sensor of proteasome dysfunction and triggers compensatory upregulation of proteasome subunit genes. Here, we show that the PNG-1/NGLY1 peptide:N-glycanase edits the sequence of SKN-1A protein by converting particular N-glycosylated asparagine residues to aspartic acid. Genetically introducing aspartates at these N-glycosylation sites bypasses the requirement for PNG-1/NGLY1, showing that protein sequence editing rather than deglycosylation is key to SKN-1A function. This pathway is required to maintain sufficient proteasome expression and activity, and SKN-1A hyperactivation confers resistance to the proteotoxicity of human amyloid beta peptide. Deglycosylation-dependent protein sequence editing explains how ER-associated and cytosolic isoforms of SKN-1 perform distinct cytoprotective functions corresponding to those of mammalian Nrf1 and Nrf2. Thus, we uncover an unexpected mechanism by which N-linked glycosylation regulates protein function and proteostasis.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Unión al ADN/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Factores de Transcripción/metabolismo , Secuencia de Aminoácidos , Animales , Asparagina/metabolismo , Bortezomib/farmacología , Sistemas CRISPR-Cas/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/química , Proteínas de Caenorhabditis elegans/genética , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Retículo Endoplásmico/metabolismo , Edición Génica , Regulación de la Expresión Génica/efectos de los fármacos , Estrés Oxidativo , Complejo de la Endopetidasa Proteasomal/genética , Subunidades de Proteína/química , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , Alineación de Secuencia , Factores de Transcripción/química , Factores de Transcripción/genéticaRESUMEN
Genomic instability in disease and its fidelity in health depend on the DNA damage response (DDR), regulated in part from the complex of meiotic recombination 11 homolog 1 (MRE11), ATP-binding cassette-ATPase (RAD50), and phosphopeptide-binding Nijmegen breakage syndrome protein 1 (NBS1). The MRE11-RAD50-NBS1 (MRN) complex forms a multifunctional DDR machine. Within its network assemblies, MRN is the core conductor for the initial and sustained responses to DNA double-strand breaks, stalled replication forks, dysfunctional telomeres, and viral DNA infection. MRN can interfere with cancer therapy and is an attractive target for precision medicine. Its conformations change the paradigm whereby kinases initiate damage sensing. Delineated results reveal kinase activation, posttranslational targeting, functional scaffolding, conformations storing binding energy and enabling access, interactions with hub proteins such as replication protein A (RPA), and distinct networks at DNA breaks and forks. MRN biochemistry provides prototypic insights into how it initiates, implements, and regulates multifunctional responses to genomic stress.
Asunto(s)
Daño del ADN , Reparación del ADN , Replicación del ADN , Proteína Homóloga de MRE11/metabolismo , Enzimas Reparadoras del ADN/química , Enzimas Reparadoras del ADN/genética , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Humanos , Inmunidad Innata , Proteína Homóloga de MRE11/química , Proteína Homóloga de MRE11/genética , Modelos Biológicos , Modelos Moleculares , Transducción de Señal , Telómero/metabolismoRESUMEN
The transcription factor ThPOK (encoded by the Zbtb7b gene) controls homeostasis and differentiation of mature helper T cells, while opposing their differentiation to CD4+ intraepithelial lymphocytes (IELs) in the intestinal mucosa. Thus CD4 IEL differentiation requires ThPOK transcriptional repression via reactivation of the ThPOK transcriptional silencer element (SilThPOK). In the present study, we describe a new autoregulatory loop whereby ThPOK binds to the SilThPOK to maintain its own long-term expression in CD4 T cells. Disruption of this loop in vivo prevents persistent ThPOK expression, leads to genome-wide changes in chromatin accessibility and derepresses the colonic regulatory T (Treg) cell gene expression signature. This promotes selective differentiation of naive CD4 T cells into GITRloPD-1loCD25lo (Triplelo) Treg cells and conversion to CD4+ IELs in the gut, thereby providing dominant protection from colitis. Hence, the ThPOK autoregulatory loop represents a key mechanism to physiologically control ThPOK expression and T cell differentiation in the gut, with potential therapeutic relevance.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Linfocitos Intraepiteliales/citología , Linfocitos T Colaboradores-Inductores/citología , Linfocitos T Reguladores/citología , Factores de Transcripción/metabolismo , Animales , Diferenciación Celular/inmunología , Colitis/inmunología , Colitis/prevención & control , Proteínas de Unión al ADN/genética , Modelos Animales de Enfermedad , Femenino , Mucosa Intestinal/citología , Mucosa Intestinal/inmunología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Linfocitos T Colaboradores-Inductores/inmunología , Linfocitos T Reguladores/inmunología , Factores de Transcripción/genética , Transcripción Genética/genéticaRESUMEN
Transcription factors specialized to limit the destructive potential of inflammatory immune cells remain ill-defined. We discovered loss-of-function variants in the X-linked ETS transcription factor gene ELF4 in multiple unrelated male patients with early onset mucosal autoinflammation and inflammatory bowel disease (IBD) characteristics, including fevers and ulcers that responded to interleukin-1 (IL-1), tumor necrosis factor or IL-12p40 blockade. Using cells from patients and newly generated mouse models, we uncovered ELF4-mutant macrophages having hyperinflammatory responses to a range of innate stimuli. In mouse macrophages, Elf4 both sustained the expression of anti-inflammatory genes, such as Il1rn, and limited the upregulation of inflammation amplifiers, including S100A8, Lcn2, Trem1 and neutrophil chemoattractants. Blockade of Trem1 reversed inflammation and intestine pathology after in vivo lipopolysaccharide challenge in mice carrying patient-derived variants in Elf4. Thus, ELF4 restrains inflammation and protects against mucosal disease, a discovery with broad translational relevance for human inflammatory disorders such as IBD.
Asunto(s)
Proteínas de Unión al ADN/genética , Enfermedades Autoinflamatorias Hereditarias/genética , Enfermedades Inflamatorias del Intestino/genética , Macrófagos/inmunología , Factores de Transcripción/genética , Animales , Calgranulina A/metabolismo , Femenino , Regulación de la Expresión Génica/genética , Enfermedades Autoinflamatorias Hereditarias/inmunología , Enfermedades Autoinflamatorias Hereditarias/patología , Humanos , Enfermedades Inflamatorias del Intestino/inmunología , Enfermedades Inflamatorias del Intestino/patología , Proteína Antagonista del Receptor de Interleucina 1/inmunología , Lipocalina 2/metabolismo , Lipopolisacáridos/toxicidad , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Células Th17/inmunología , Transcripción Genética/genética , Receptor Activador Expresado en Células Mieloides 1/antagonistas & inhibidores , Receptor Activador Expresado en Células Mieloides 1/metabolismoRESUMEN
During the germinal center (GC) reaction, B cells undergo extensive redistribution of cohesin complex and three-dimensional reorganization of their genomes. Yet, the significance of cohesin and architectural programming in the humoral immune response is unknown. Herein we report that homozygous deletion of Smc3, encoding the cohesin ATPase subunit, abrogated GC formation, while, in marked contrast, Smc3 haploinsufficiency resulted in GC hyperplasia, skewing of GC polarity and impaired plasma cell (PC) differentiation. Genome-wide chromosomal conformation and transcriptional profiling revealed defects in GC B cell terminal differentiation programs controlled by the lymphoma epigenetic tumor suppressors Tet2 and Kmt2d and failure of Smc3-haploinsufficient GC B cells to switch from B cell- to PC-defining transcription factors. Smc3 haploinsufficiency preferentially impaired the connectivity of enhancer elements controlling various lymphoma tumor suppressor genes, and, accordingly, Smc3 haploinsufficiency accelerated lymphomagenesis in mice with constitutive Bcl6 expression. Collectively, our data indicate a dose-dependent function for cohesin in humoral immunity to facilitate the B cell to PC phenotypic switch while restricting malignant transformation.
Asunto(s)
Linfocitos B/metabolismo , Proteínas de Ciclo Celular/deficiencia , Proteínas de Ciclo Celular/genética , Transformación Celular Neoplásica/genética , Proteoglicanos Tipo Condroitín Sulfato/genética , Proteínas Cromosómicas no Histona/deficiencia , Proteínas Cromosómicas no Histona/genética , Dosificación de Gen , Centro Germinal/metabolismo , Inmunidad Humoral , Linfoma de Células B/genética , Animales , Linfocitos B/inmunología , Linfocitos B/patología , Proteínas de Ciclo Celular/metabolismo , Diferenciación Celular , Proliferación Celular , Transformación Celular Neoplásica/inmunología , Transformación Celular Neoplásica/metabolismo , Transformación Celular Neoplásica/patología , Células Cultivadas , Proteoglicanos Tipo Condroitín Sulfato/deficiencia , Proteoglicanos Tipo Condroitín Sulfato/metabolismo , Proteínas Cromosómicas no Histona/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Dioxigenasas , Eliminación de Gen , Regulación Neoplásica de la Expresión Génica , Centro Germinal/inmunología , Centro Germinal/patología , Haploinsuficiencia , N-Metiltransferasa de Histona-Lisina/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , Humanos , Linfoma de Células B/inmunología , Linfoma de Células B/metabolismo , Linfoma de Células B/patología , Linfoma de Células B Grandes Difuso/genética , Linfoma de Células B Grandes Difuso/inmunología , Linfoma de Células B Grandes Difuso/metabolismo , Linfoma de Células B Grandes Difuso/patología , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína de la Leucemia Mieloide-Linfoide/genética , Proteína de la Leucemia Mieloide-Linfoide/metabolismo , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/metabolismo , Transducción de Señal , CohesinasRESUMEN
Expression of the transcriptional regulator ZFP318 is induced in germinal center (GC)-exiting memory B cell precursors and memory B cells (MBCs). Using a conditional ZFP318 fluorescence reporter that also enables ablation of ZFP318-expressing cells, we found that ZFP318-expressing MBCs were highly enriched with GC-derived cells. Although ZFP318-expressing MBCs constituted only a minority of the antigen-specific MBC compartment, their ablation severely impaired recall responses. Deletion of Zfp318 did not alter the magnitude of primary responses but markedly reduced MBC participation in recall. CD40 ligation promoted Zfp318 expression, whereas B cell receptor (BCR) signaling was inhibitory. Enforced ZFP318 expression enhanced recall performance of MBCs that otherwise responded poorly. ZFP318-deficient MBCs expressed less mitochondrial genes, had structurally compromised mitochondria, and were susceptible to reactivation-induced cell death. The abundance of ZFP318-expressing MBCs, instead of the number of antigen-specific MBCs, correlated with the potency of prime-boost vaccination. Therefore, ZFP318 controls the MBC recallability and represents a quality checkpoint of humoral immune memory.
Asunto(s)
Centro Germinal , Memoria Inmunológica , Células B de Memoria , Mitocondrias , Animales , Mitocondrias/metabolismo , Mitocondrias/inmunología , Ratones , Memoria Inmunológica/genética , Memoria Inmunológica/inmunología , Células B de Memoria/inmunología , Células B de Memoria/metabolismo , Centro Germinal/inmunología , Receptores de Antígenos de Linfocitos B/metabolismo , Receptores de Antígenos de Linfocitos B/genética , Regulación de la Expresión Génica , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Ratones Endogámicos C57BL , Ratones Noqueados , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Transducción de Señal/inmunología , Antígenos CD40/metabolismo , Antígenos CD40/genética , Antígenos CD40/inmunología , Inmunidad Humoral , Transcripción Genética , Proteínas de la Membrana , Proteínas MitocondrialesRESUMEN
Mitochondrial DNA is compacted into nucleoprotein complexes denoted mitochondrial nucleoids, the focus of this SnapShot.