RESUMO
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.
Assuntos
Desmetilação do DNA , Dioxigenases , Imunoterapia , Inflamação , Neoplasias , Humanos , Neoplasias/terapia , Neoplasias/imunologia , Neoplasias/etiologia , Neoplasias/metabolismo , Animais , Inflamação/metabolismo , Inflamação/imunologia , Imunoterapia/métodos , Dioxigenases/metabolismo , Sistema Imunitário/metabolismo , Sistema Imunitário/imunologia , Epigênese Genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas/genética , Metilação de DNA , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Oxigenases de Função Mista/metabolismo , Oxigenases de Função Mista/genéticaRESUMO
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.
Assuntos
Diferenciação Celular/imunologia , Linfócitos T Citotóxicos/citologia , Linfócitos T Citotóxicos/imunologia , Linfócitos T Auxiliares-Indutores/citologia , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Antígenos CD4/genética , Antígenos CD4/metabolismo , Antígenos CD8/genética , Antígenos CD8/metabolismo , Diferenciação Celular/genética , Linhagem da Célula/genética , Linhagem da Célula/imunologia , Subunidade alfa 3 de Fator de Ligação ao Core/genética , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica , Humanos , Imunomodulação/genética , Imunomodulação/imunologia , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/metabolismo , Sequências Reguladoras de Ácido Nucleico , Linfócitos T Citotóxicos/metabolismo , Linfócitos T Auxiliares-Indutores/metabolismo , Fatores de Transcrição/genética , Transcrição GênicaRESUMO
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.
Assuntos
Reparo do DNA , Proteínas de Saccharomyces cerevisiae , Animais , DNA/genética , DNA/metabolismo , Dano ao DNA , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Instabilidade Genômica , Camundongos , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
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.
Assuntos
RNA Polimerase II/metabolismo , Sequências Reguladoras de Ácido Nucleico , Fator de Transcrição TFIID/genética , Fator de Transcrição TFIIH/genética , Iniciação da Transcrição Genética/fisiologia , Reparo do DNA/fisiologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Humanos , Complexo Mediador/genética , Complexo Mediador/metabolismo , Mutação , Regiões Promotoras Genéticas , RNA Polimerase II/genética , SíndromeRESUMO
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.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Impressão Genômica , Heterocromatina/metabolismo , Proteínas do Grupo Polycomb/genética , Inativação do Cromossomo X , Cromossomo X/metabolismo , Animais , Montagem e Desmontagem da Cromatina , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Embrião de Mamíferos , Feminino , Inativação Gênica , Heterocromatina/química , Histona Desacetilases/genética , Histona Desacetilases/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Masculino , Oócitos/citologia , Oócitos/crescimento & desenvolvimento , Oócitos/metabolismo , Proteínas do Grupo Polycomb/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Espermatozoides/citologia , Espermatozoides/crescimento & desenvolvimento , Espermatozoides/metabolismo , Cromossomo X/químicaRESUMO
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.
Assuntos
Trifosfato de Adenosina/genética , DNA Helicases/genética , Enzimas Reparadoras do DNA/genética , DNA/genética , Recombinação Homóloga/genética , Proteínas de Saccharomyces cerevisiae/genética , Adenosina Trifosfatases/genética , Dano ao DNA/genética , Reparo do DNA/genética , Proteínas de Ligação a DNA/genética , Hidrólise , Saccharomyces cerevisiae/genética , Alinhamento de Sequência/métodosRESUMO
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.
Assuntos
Bacteriófago mu/genética , Cromossomos Bacterianos/genética , Elementos de DNA Transponíveis , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Cromossomos Bacterianos/química , DNA Bacteriano/química , DNA Bacteriano/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Escherichia coli , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Genoma Bacteriano , Conformação de Ácido Nucleico , Transposases/genética , Transposases/metabolismoRESUMO
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.
Assuntos
Evolução Clonal/genética , Colite/genética , Doenças Inflamatórias Intestinais/genética , Taxa de Mutação , Adulto , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/genética , Evolução Clonal/imunologia , Colite/metabolismo , Colite Ulcerativa/genética , Colite Ulcerativa/metabolismo , Doença de Crohn/genética , Doença de Crohn/metabolismo , Proteínas de Ligação a DNA/genética , Células Epiteliais/metabolismo , Células Epiteliais/patologia , Proteína 7 com Repetições F-Box-WD/genética , Feminino , Humanos , Mutação INDEL , Doenças Inflamatórias Intestinais/imunologia , Doenças Inflamatórias Intestinais/metabolismo , Doenças Inflamatórias Intestinais/patologia , Interleucina-17/metabolismo , Mucosa Intestinal/metabolismo , Mucosa Intestinal/patologia , Masculino , Pessoa de Meia-Idade , Filogenia , Mutação Puntual , Receptores de Superfície Celular/genética , Ribonucleases/genética , Receptores Toll-Like/genética , Fatores de Transcrição/genética , Sequenciamento Completo do GenomaRESUMO
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.
Assuntos
Neoplasias Encefálicas/metabolismo , Carcinogênese/metabolismo , Transformação Celular Neoplásica/metabolismo , Dinâmica Mitocondrial , NAD/metabolismo , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neurais/metabolismo , Fosforilação Oxidativa , Animais , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/mortalidade , Neoplasias Encefálicas/patologia , Carcinogênese/genética , Carcinogênese/patologia , Transformação Celular Neoplásica/patologia , Ciclo do Ácido Cítrico/genética , Biologia Computacional , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Drosophila , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Glicólise/genética , Espectrometria de Massas , Metabolômica , Microscopia Eletrônica de Transmissão , Família Multigênica , Células-Tronco Neurais/patologia , Consumo de Oxigênio/genética , Interferência de RNA , Espécies Reativas de Oxigênio/metabolismo , Análise de Célula Única , Transcriptoma/genéticaRESUMO
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.
Assuntos
Linfócitos B , Proteínas de Ligação a DNA , Proteínas de Homeodomínio , Proteínas Nucleares , Diferenciação Celular , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/genética , Proteínas de Homeodomínio/genética , Humanos , Tolerância Imunológica , Contagem de Linfócitos , Proteínas Nucleares/deficiênciaRESUMO
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.
Assuntos
5-Metilcitosina/análogos & derivados , Reparo do DNA/fisiologia , DNA de Cadeia Simples/fisiologia , 5-Metilcitosina/metabolismo , Ácido Apurínico/metabolismo , DNA/metabolismo , Dano ao DNA/fisiologia , Replicação do DNA/fisiologia , DNA de Cadeia Simples/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Endonucleases , Escherichia coli/metabolismo , Polinucleotídeos/metabolismo , Antígeno Nuclear de Célula em Proliferação/metabolismoRESUMO
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.
Assuntos
Doença de Alzheimer/patologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Ataxina-1/metabolismo , Encéfalo/metabolismo , Doença de Alzheimer/metabolismo , Secretases da Proteína Precursora do Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Ataxina-1/deficiência , Ataxina-1/genética , Encéfalo/patologia , Região CA2 Hipocampal/metabolismo , Região CA2 Hipocampal/patologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Modelos Animais de Doenças , Feminino , Frequência do Gene , Humanos , Masculino , Camundongos , Camundongos Transgênicos , Neurogênese , Proteínas Proto-Oncogênicas c-ets/genética , Proteínas Proto-Oncogênicas c-ets/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica , Repetições de Trinucleotídeos/genética , Regulação para CimaRESUMO
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.
Assuntos
Hepatopatias/patologia , Fígado/metabolismo , Regeneração , Animais , Doença Crônica , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Feminino , Humanos , Hidrolases/deficiência , Hidrolases/genética , Fígado/patologia , Cirrose Hepática/induzido quimicamente , Cirrose Hepática/genética , Cirrose Hepática/patologia , Hepatopatias/genética , Masculino , Camundongos , Camundongos Knockout , Pessoa de Meia-Idade , Mutação , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Regeneração/fisiologia , Canais de Cátion TRPP/genética , Canais de Cátion TRPP/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Sequenciamento do ExomaRESUMO
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.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Ligação a DNA/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Animais , Asparagina/metabolismo , Bortezomib/farmacologia , Sistemas CRISPR-Cas/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/química , Proteínas de Caenorhabditis elegans/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Retículo Endoplasmático/metabolismo , Edição de Genes , Regulação da Expressão Gênica/efeitos dos fármacos , Estresse Oxidativo , Complexo de Endopeptidases do Proteassoma/genética , Subunidades Proteicas/química , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Alinhamento de Sequência , Fatores de Transcrição/química , Fatores de Transcrição/genéticaRESUMO
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.
Assuntos
Dano ao DNA , Reparo do DNA , Replicação do DNA , Proteína Homóloga a MRE11/metabolismo , Enzimas Reparadoras do DNA/química , Enzimas Reparadoras do DNA/genética , Enzimas Reparadoras do DNA/metabolismo , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Humanos , Imunidade Inata , Proteína Homóloga a MRE11/química , Proteína Homóloga a MRE11/genética , Modelos Biológicos , Modelos Moleculares , Transdução de Sinais , Telômero/metabolismoRESUMO
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.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Linfócitos Intraepiteliais/citologia , Linfócitos T Auxiliares-Indutores/citologia , Linfócitos T Reguladores/citologia , Fatores de Transcrição/metabolismo , Animais , Diferenciação Celular/imunologia , Colite/imunologia , Colite/prevenção & controle , Proteínas de Ligação a DNA/genética , Modelos Animais de Doenças , Feminino , Mucosa Intestinal/citologia , Mucosa Intestinal/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Reguladores/imunologia , Fatores de Transcrição/genética , Transcrição Gênica/genéticaRESUMO
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.
Assuntos
Proteínas de Ligação a DNA/genética , Doenças Hereditárias Autoinflamatórias/genética , Doenças Inflamatórias Intestinais/genética , Macrófagos/imunologia , Fatores de Transcrição/genética , Animais , Calgranulina A/metabolismo , Feminino , Regulação da Expressão Gênica/genética , Doenças Hereditárias Autoinflamatórias/imunologia , Doenças Hereditárias Autoinflamatórias/patologia , Humanos , Doenças Inflamatórias Intestinais/imunologia , Doenças Inflamatórias Intestinais/patologia , Proteína Antagonista do Receptor de Interleucina 1/imunologia , Lipocalina-2/metabolismo , Lipopolissacarídeos/toxicidade , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células Th17/imunologia , Transcrição Gênica/genética , Receptor Gatilho 1 Expresso em Células Mieloides/antagonistas & inibidores , Receptor Gatilho 1 Expresso em Células Mieloides/metabolismoRESUMO
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.
Assuntos
Linfócitos B/metabolismo , Proteínas de Ciclo Celular/deficiência , Proteínas de Ciclo Celular/genética , Transformação Celular Neoplásica/genética , Proteoglicanas de Sulfatos de Condroitina/genética , Proteínas Cromossômicas não Histona/deficiência , Proteínas Cromossômicas não Histona/genética , Dosagem de Genes , Centro Germinativo/metabolismo , Imunidade Humoral , Linfoma de Células B/genética , Animais , Linfócitos B/imunologia , Linfócitos B/patologia , Proteínas de Ciclo Celular/metabolismo , Diferenciação Celular , Proliferação de Células , Transformação Celular Neoplásica/imunologia , Transformação Celular Neoplásica/metabolismo , Transformação Celular Neoplásica/patologia , Células Cultivadas , Proteoglicanas de Sulfatos de Condroitina/deficiência , Proteoglicanas de Sulfatos de Condroitina/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Dioxigenases , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Centro Germinativo/imunologia , Centro Germinativo/patologia , Haploinsuficiência , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Humanos , Linfoma de Células B/imunologia , Linfoma de Células B/metabolismo , Linfoma de Células B/patologia , Linfoma Difuso de Grandes Células B/genética , Linfoma Difuso de Grandes Células B/imunologia , Linfoma Difuso de Grandes Células B/metabolismo , Linfoma Difuso de Grandes Células B/patologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína de Leucina Linfoide-Mieloide/genética , Proteína de Leucina Linfoide-Mieloide/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Transdução de Sinais , CoesinasRESUMO
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.
Assuntos
Centro Germinativo , Memória Imunológica , Células B de Memória , Mitocôndrias , Animais , Mitocôndrias/metabolismo , Mitocôndrias/imunologia , Camundongos , Memória Imunológica/genética , Memória Imunológica/imunologia , Células B de Memória/imunologia , Células B de Memória/metabolismo , Centro Germinativo/imunologia , Receptores de Antígenos de Linfócitos B/metabolismo , Receptores de Antígenos de Linfócitos B/genética , Regulação da Expressão Gênica , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Transdução de Sinais/imunologia , Antígenos CD40/metabolismo , Antígenos CD40/genética , Antígenos CD40/imunologia , Imunidade Humoral , Transcrição Gênica , Proteínas de Membrana , Proteínas MitocondriaisRESUMO
Mitochondrial DNA is compacted into nucleoprotein complexes denoted mitochondrial nucleoids, the focus of this SnapShot.