RESUMEN
Viral and cellular double-stranded RNA (dsRNA) is recognized by cytosolic innate immune sensors, including RIG-I-like receptors. Some cytoplasmic dsRNA is commonly present in cells, and one source is mitochondrial dsRNA, which results from bidirectional transcription of mitochondrial DNA (mtDNA). Here we demonstrate that Trp53 mutant mouse embryonic fibroblasts contain immune-stimulating endogenous dsRNA of mitochondrial origin. We show that the immune response induced by this dsRNA is mediated via RIG-I-like receptors and leads to the expression of type I interferon and proinflammatory cytokine genes. The mitochondrial dsRNA is cleaved by RNase L, which cleaves all cellular RNA including mitochondrial mRNAs, increasing activation of RIG-I-like receptors. When mitochondrial transcription is interrupted there is a subsequent decrease in this immune-stimulatory dsRNA. Our results reveal that the role of p53 in innate immunity is even more versatile and complex than previously anticipated. Our study, therefore, sheds new light on the role of endogenous RNA in diseases featuring aberrant immune responses.
Asunto(s)
Adenosina Desaminasa/genética , Proteína 58 DEAD Box/genética , Inmunidad Innata/genética , ARN Bicatenario/genética , ARN Mitocondrial/genética , Proteína p53 Supresora de Tumor/genética , Proteínas Adaptadoras Transductoras de Señales , Adenosina Desaminasa/deficiencia , Adenosina Desaminasa/inmunología , Animales , Proteínas Portadoras/genética , Proteínas Portadoras/inmunología , Proteína 58 DEAD Box/inmunología , Embrión de Mamíferos , Endorribonucleasas/genética , Endorribonucleasas/inmunología , Fibroblastos/citología , Fibroblastos/inmunología , Factor 7 Regulador del Interferón/genética , Factor 7 Regulador del Interferón/inmunología , Helicasa Inducida por Interferón IFIH1/genética , Helicasa Inducida por Interferón IFIH1/inmunología , Péptidos y Proteínas de Señalización Intracelular , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas/genética , Proteínas/inmunología , ARN Bicatenario/inmunología , ARN Mitocondrial/inmunología , Proteínas de Unión al ARN , Transcripción Genética , Transfección , Proteína p53 Supresora de Tumor/deficiencia , Proteína p53 Supresora de Tumor/inmunologíaRESUMEN
Mouse Hsp70 (70 kDa heat shock protein) is preferentially induced by heat or stress stimuli. We previously found that Hsp70 is constitutively expressed in A6 mouse mesoangioblast stem cells, but its possible role in these cells and the control of its basal transcription remained unexplored. Here we report that in the absence of stress, Ku factor is able to bind the HSE (heat shock element) consensus sequence in vitro, and in vivo it is bound to the proximal hsp70 promoter. In addition, we show that constitutive hsp70 transcription depends on the co-operative interaction of different factors such as Sp1 (specificity protein 1) and GAGA-binding protein with Ku factor, which binds the HSE consensus sequence. We used mRNA interference assays to select knockdown cell clones. These cells were able to respond to heat stress by producing a large amount of Hsp70, and produced the same amount of Hsp70 as that synthesized by stressed A6 cells. However, severe Hsp70 knockdown cells had a longer duplication time, suggesting that constitutive Hsp70 expression has an effect on the rate of proliferation.