RESUMEN
Ageing is a degenerative process that leads to tissue dysfunction and death. A proposed cause of ageing is the accumulation of epigenetic noise that disrupts gene expression patterns, leading to decreases in tissue function and regenerative capacity1-3. Changes to DNA methylation patterns over time form the basis of ageing clocks4, but whether older individuals retain the information needed to restore these patterns-and, if so, whether this could improve tissue function-is not known. Over time, the central nervous system (CNS) loses function and regenerative capacity5-7. Using the eye as a model CNS tissue, here we show that ectopic expression of Oct4 (also known as Pou5f1), Sox2 and Klf4 genes (OSK) in mouse retinal ganglion cells restores youthful DNA methylation patterns and transcriptomes, promotes axon regeneration after injury, and reverses vision loss in a mouse model of glaucoma and in aged mice. The beneficial effects of OSK-induced reprogramming in axon regeneration and vision require the DNA demethylases TET1 and TET2. These data indicate that mammalian tissues retain a record of youthful epigenetic information-encoded in part by DNA methylation-that can be accessed to improve tissue function and promote regeneration in vivo.
Asunto(s)
Envejecimiento/genética , Reprogramación Celular/genética , Metilación de ADN , Epigénesis Genética , Ojo , Regeneración Nerviosa/genética , Visión Ocular/genética , Visión Ocular/fisiología , Envejecimiento/fisiología , Animales , Axones/fisiología , Línea Celular Tumoral , Supervivencia Celular , Proteínas de Unión al ADN/genética , Dependovirus/genética , Dioxigenasas , Modelos Animales de Enfermedad , Ojo/citología , Ojo/inervación , Ojo/patología , Femenino , Vectores Genéticos/genética , Glaucoma/genética , Glaucoma/patología , Humanos , Factor 4 Similar a Kruppel , Factores de Transcripción de Tipo Kruppel/genética , Ratones , Ratones Endogámicos C57BL , Factor 3 de Transcripción de Unión a Octámeros/genética , Traumatismos del Nervio Óptico/genética , Proteínas Proto-Oncogénicas/genética , Células Ganglionares de la Retina/citología , Factores de Transcripción SOXB1/genética , Transcriptoma/genéticaRESUMEN
DNA repair is essential for life, yet its efficiency declines with age for reasons that are unclear. Numerous proteins possess Nudix homology domains (NHDs) that have no known function. We show that NHDs are NAD+ (oxidized form of nicotinamide adenine dinucleotide) binding domains that regulate protein-protein interactions. The binding of NAD+ to the NHD domain of DBC1 (deleted in breast cancer 1) prevents it from inhibiting PARP1 [poly(adenosine diphosphate-ribose) polymerase], a critical DNA repair protein. As mice age and NAD+ concentrations decline, DBC1 is increasingly bound to PARP1, causing DNA damage to accumulate, a process rapidly reversed by restoring the abundance of NAD+ Thus, NAD+ directly regulates protein-protein interactions, the modulation of which may protect against cancer, radiation, and aging.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Envejecimiento/metabolismo , Reparación del ADN , NAD/metabolismo , Poli(ADP-Ribosa) Polimerasa-1/metabolismo , Proteínas Adaptadoras Transductoras de Señales/química , Proteínas Adaptadoras Transductoras de Señales/genética , Envejecimiento/genética , Animales , Secuencia Conservada , Daño del ADN/genética , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Células HEK293 , Humanos , Ratones , Modelos Moleculares , Neoplasias/genética , Neoplasias/metabolismo , Paraquat/farmacología , Poli(ADP-Ribosa) Polimerasa-1/química , Poli(ADP-Ribosa) Polimerasa-1/genética , Dominios y Motivos de Interacción de Proteínas , ARN Interferente Pequeño/genética , Tolerancia a Radiación/genética , Homología de Secuencia de Ácido NucleicoRESUMEN
Rearrangements between tandemly repeated DNA sequences are a common source of genetic instability. Such rearrangements underlie several human genetic diseases. In many organisms, the mismatch-repair (MMR) system functions to stabilize repeats when the repeat unit is short or when sequence imperfections are present between the repeats. We show here that the action of single-stranded DNA (ssDNA) exonucleases plays an additional, important role in stabilizing tandem repeats, independent of their role in MMR. For perfect repeats of approximately 100 bp in Escherichia coli that are not susceptible to MMR, exonuclease (Exo)-I, ExoX, and RecJ exonuclease redundantly inhibit deletion. Our data suggest that >90% of potential deletion events are avoided by the combined action of these three exonucleases. Imperfect tandem repeats, less prone to rearrangements, are stabilized by both the MMR-pathway and ssDNA-specific exonucleases. For 100-bp repeats containing four mispairs, ExoI alone aborts most deletion events, even in the presence of a functional MMR system. By genetic analysis, we show that the inhibitory effect of ssDNA exonucleases on deletion formation is independent of the MutS and UvrD proteins. Exonuclease degradation of DNA displaced during the deletion process may abort slipped misalignment. Exonuclease action is therefore a significant force in genetic stabilization of many forms of repetitive DNA.