RESUMEN
Hard-to-replicate regions of chromosomes (e.g., pericentromeres, centromeres, and telomeres) impede replication fork progression, eventually leading, in the event of replication stress, to chromosome fragility, aging, and cancer. Our knowledge of the mechanisms controlling the stability of these regions is essentially limited to telomeres, where fragility is counteracted by the shelterin proteins. Here we show that the shelterin subunit TRF2 ensures progression of the replication fork through pericentromeric heterochromatin, but not centromeric chromatin. In a process involving its N-terminal basic domain, TRF2 binds to pericentromeric Satellite III sequences during S phase, allowing the recruitment of the G-quadruplex-resolving helicase RTEL1 to facilitate fork progression. We also show that TRF2 is required for the stability of other heterochromatic regions localized throughout the genome, paving the way for future research on heterochromatic replication and its relationship with aging and cancer.
Asunto(s)
Replicación del ADN/genética , Genoma/genética , Heterocromatina/genética , Telómero/genética , Proteína 2 de Unión a Repeticiones Teloméricas/genética , Línea Celular Tumoral , Centrómero/genética , Cromatina/genética , ADN Helicasas/genética , G-Cuádruplex , Células HeLa , Humanos , Fase S/genéticaRESUMEN
Telomeres protect chromosome ends from degradation and inappropriate DNA damage response activation through their association with specific factors. Interestingly, these telomeric factors are able to localize outside telomeric regions, where they can regulate the transcription of genes involved in metabolism, immunity and differentiation. These findings delineate a signalling pathway by which telomeric changes control the ability of their associated factors to regulate transcription. This mechanism is expected to enable a greater diversity of cellular responses that are adapted to specific cell types and telomeric changes, and may therefore represent a pivotal aspect of development, ageing and telomere-mediated diseases.
Asunto(s)
Reparación del ADN , Transducción de Señal/genética , Telómero/química , Transcripción Genética , Apoptosis , Senescencia Celular , Daño del ADN , Regulación de la Expresión Génica , Humanos , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Complejo Shelterina , Telomerasa/genética , Telomerasa/metabolismo , Telómero/metabolismo , Proteínas de Unión a Telómeros/genética , Proteínas de Unión a Telómeros/metabolismo , Proteína 2 de Unión a Repeticiones Teloméricas/genética , Proteína 2 de Unión a Repeticiones Teloméricas/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Aging is a multifactorial process that results in progressive loss of regenerative capacity and tissue function while simultaneously favoring the development of a large array of age-related diseases. Evidence suggests that the accumulation of senescent cells in tissue promotes both normal and pathological aging. Oxic stress is a key driver of cellular senescence. Because symbiotic long-lived reef corals experience daily hyperoxic and hypoxic transitions, we hypothesized that these long-lived animals have developed specific longevity strategies in response to light. We analyzed transcriptome variation in the reef coral Stylophora pistillata during the day-night cycle and revealed a signature of the FoxO longevity pathway. We confirmed this pathway by immunofluorescence using antibodies against coral FoxO to demonstrate its nuclear translocation. Through qPCR analysis of nycthemeral variations of candidate genes under different light regimens, we found that, among genes that were specifically up- or downregulated upon exposure to light, human orthologs of two "light-up" genes (HEY1 and LONF3) exhibited anti-senescence properties in primary human fibroblasts. Therefore, these genes are interesting candidates for counteracting skin aging. We propose a large screen for other light-up genes and an investigation of the biological response of reef corals to light (e.g., metabolic switching) to elucidate these processes and identify effective interventions for promoting healthy aging in humans.
Asunto(s)
Antozoos/fisiología , Arrecifes de Coral , Factores de Transcripción Forkhead/metabolismo , Luz , Longevidad , Fotosíntesis , Animales , Antozoos/efectos de la radiación , Factores de Transcripción Forkhead/genéticaRESUMEN
Dysfunctional telomeres suppress tumour progression by activating cell-intrinsic programs that lead to growth arrest. Increased levels of TRF2, a key factor in telomere protection, are observed in various human malignancies and contribute to oncogenesis. We demonstrate here that a high level of TRF2 in tumour cells decreased their ability to recruit and activate natural killer (NK) cells. Conversely, a reduced dose of TRF2 enabled tumour cells to be more easily eliminated by NK cells. Consistent with these results, a progressive upregulation of TRF2 correlated with decreased NK cell density during the early development of human colon cancer. By screening for TRF2-bound genes, we found that HS3ST4--a gene encoding for the heparan sulphate (glucosamine) 3-O-sulphotransferase 4--was regulated by TRF2 and inhibited the recruitment of NK cells in an epistatic relationship with TRF2. Overall, these results reveal a TRF2-dependent pathway that is tumour-cell extrinsic and regulates NK cell immunity.
Asunto(s)
Neoplasias de la Mama/prevención & control , Neoplasias del Colon/prevención & control , Células Asesinas Naturales/inmunología , Linfocitos Infiltrantes de Tumor/inmunología , Melanoma Experimental/prevención & control , Sulfotransferasas/metabolismo , Proteína 2 de Unión a Repeticiones Teloméricas/metabolismo , Animales , Apoptosis , Western Blotting , Neoplasias de la Mama/inmunología , Neoplasias de la Mama/metabolismo , Adhesión Celular , Proliferación Celular , Neoplasias del Colon/inmunología , Neoplasias del Colon/metabolismo , Cartilla de ADN/química , Receptor con Dominio Discoidina 1 , Femenino , Citometría de Flujo , Células HeLa , Humanos , Células Asesinas Naturales/metabolismo , Células Asesinas Naturales/patología , Linfocitos Infiltrantes de Tumor/patología , Melanoma Experimental/inmunología , Melanoma Experimental/metabolismo , Ratones , Ratones Desnudos , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Tirosina Quinasas Receptoras/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Sulfotransferasas/genética , Proteína 2 de Unión a Repeticiones Teloméricas/antagonistas & inhibidores , Proteína 2 de Unión a Repeticiones Teloméricas/genética , Células Tumorales CultivadasRESUMEN
Mutant screens have proven powerful for genetic dissection of a myriad of biological processes, but subsequent identification and isolation of the causative mutations are usually complex and time consuming. We have made the process easier by establishing a novel strategy that employs whole-genome sequencing to simultaneously map and identify mutations without the need for any prior genetic mapping.