RESUMO
Facioscapulohumeral dystrophy (FSHD) is caused by the mis-expression of DUX4 in skeletal muscle cells. DUX4 is a transcription factor that activates genes normally associated with stem cell biology and its mis-expression in FSHD cells results in apoptosis. To identify genes and pathways necessary for DUX4-mediated apoptosis, we performed an siRNA screen in an RD rhabdomyosarcoma cell line with an inducible DUX4 transgene. Our screen identified components of the MYC-mediated apoptotic pathway and the double-stranded RNA (dsRNA) innate immune response pathway as mediators of DUX4-induced apoptosis. Further investigation revealed that DUX4 expression led to increased MYC mRNA, accumulation of nuclear dsRNA foci, and activation of the dsRNA response pathway in both RD cells and human myoblasts. Nuclear dsRNA foci were associated with aggregation of the exon junction complex component EIF4A3. The elevation of MYC mRNA, dsRNA accumulation, and EIF4A3 nuclear aggregates in FSHD muscle cells suggest that these processes might contribute to FSHD pathophysiology.
Assuntos
Apoptose , Proteínas de Homeodomínio/genética , Distrofia Muscular Facioescapuloumeral/genética , Distrofia Muscular Facioescapuloumeral/patologia , Proteínas Proto-Oncogênicas c-myc/genética , RNA de Cadeia Dupla/genética , Rabdomiossarcoma/genética , Caspases/metabolismo , Morte Celular , Linhagem Celular , Sobrevivência Celular , RNA Helicases DEAD-box/genética , Fator de Iniciação 4A em Eucariotos/genética , Éxons , Regulação da Expressão Gênica , Humanos , Imunidade Inata , Mutação , Mioblastos/metabolismo , RNA de Cadeia Dupla/metabolismo , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Proteína Supressora de Tumor p53/genéticaRESUMO
The accumulation of damage caused by oxidative stress has been linked to aging and to the etiology of numerous age-related diseases. The longevity gene, sirtuin 6 (SIRT6), promotes genome stability by facilitating DNA repair, especially under oxidative stress conditions. Here we uncover the mechanism by which SIRT6 is activated by oxidative stress to promote DNA double-strand break (DSB) repair. We show that the stress-activated protein kinase, c-Jun N-terminal kinase (JNK), phosphorylates SIRT6 on serine 10 in response to oxidative stress. This post-translational modification facilitates the mobilization of SIRT6 to DNA damage sites and is required for efficient recruitment of poly (ADP-ribose) polymerase 1 (PARP1) to DNA break sites and for efficient repair of DSBs. Our results demonstrate a post-translational mechanism regulating SIRT6, and they provide the link between oxidative stress signaling and DNA repair pathways that may be critical for hormetic response and longevity assurance.
Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Estresse Oxidativo , Poli(ADP-Ribose) Polimerase-1/metabolismo , Sirtuínas/metabolismo , Adenosina Difosfato Ribose/metabolismo , Animais , Células HEK293 , Humanos , Camundongos Knockout , Modelos Biológicos , Fosforilação , Fosfosserina/metabolismoRESUMO
L1 retrotransposons are an abundant class of transposable elements that pose a threat to genome stability and may have a role in age-related pathologies such as cancer. Recent evidence indicates that L1s become more active in somatic tissues during the course of ageing; however the mechanisms underlying this phenomenon remain unknown. Here we report that the longevity regulating protein, SIRT6, is a powerful repressor of L1 activity. Specifically, SIRT6 binds to the 5'-UTR of L1 loci, where it mono-ADP ribosylates the nuclear corepressor protein, KAP1, and facilitates KAP1 interaction with the heterochromatin factor, HP1α, thereby contributing to the packaging of L1 elements into transcriptionally repressive heterochromatin. During the course of ageing, and also in response to DNA damage, however, we find that SIRT6 is depleted from L1 loci, allowing the activation of these previously silenced retroelements.