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Nature ; 560(7717): 238-242, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30046113

RESUMO

Mitochondria are descendants of endosymbiotic bacteria and retain essential prokaryotic features such as a compact circular genome. Consequently, in mammals, mitochondrial DNA is subjected to bidirectional transcription that generates overlapping transcripts, which are capable of forming long double-stranded RNA structures1,2. However, to our knowledge, mitochondrial double-stranded RNA has not been previously characterized in vivo. Here we describe the presence of a highly unstable native mitochondrial double-stranded RNA species at single-cell level and identify key roles for the degradosome components mitochondrial RNA helicase SUV3 and polynucleotide phosphorylase PNPase in restricting the levels of mitochondrial double-stranded RNA. Loss of either enzyme results in massive accumulation of mitochondrial double-stranded RNA that escapes into the cytoplasm in a PNPase-dependent manner. This process engages an MDA5-driven antiviral signalling pathway that triggers a type I interferon response. Consistent with these data, patients carrying hypomorphic mutations in the gene PNPT1, which encodes PNPase, display mitochondrial double-stranded RNA accumulation coupled with upregulation of interferon-stimulated genes and other markers of immune activation. The localization of PNPase to the mitochondrial inter-membrane space and matrix suggests that it has a dual role in preventing the formation and release of mitochondrial double-stranded RNA into the cytoplasm. This in turn prevents the activation of potent innate immune defence mechanisms that have evolved to protect vertebrates against microbial and viral attack.


Assuntos
Herpesvirus Humano 1/imunologia , RNA de Cadeia Dupla/imunologia , RNA Mitocondrial/imunologia , Animais , RNA Helicases DEAD-box/deficiência , RNA Helicases DEAD-box/genética , RNA Helicases DEAD-box/metabolismo , Endorribonucleases/metabolismo , Exorribonucleases/deficiência , Exorribonucleases/genética , Exorribonucleases/metabolismo , Regulação da Expressão Gênica/imunologia , Células HeLa , Herpesvirus Humano 1/genética , Humanos , Interferon Tipo I/antagonistas & inibidores , Interferon Tipo I/imunologia , Helicase IFIH1 Induzida por Interferon/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Complexos Multienzimáticos/metabolismo , Mutação , Polirribonucleotídeo Nucleotidiltransferase/metabolismo , RNA Helicases/metabolismo , Análise de Célula Única , Proteína Killer-Antagonista Homóloga a bcl-2/metabolismo , Proteína X Associada a bcl-2/metabolismo
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