RESUMO
Aicardi-Goutières syndrome (AGS) provides a monogenic model of nucleic acid-mediated inflammation relevant to the pathogenesis of systemic autoimmunity. Mutations that impair ribonuclease (RNase) H2 enzyme function are the most frequent cause of this autoinflammatory disorder of childhood and are also associated with systemic lupus erythematosus. Reduced processing of eitherRNA:DNAhybrid or genome-embedded ribonucleotide substrates is thought to lead to activation of a yet undefined nucleic acid-sensing pathway. Here, we establishRnaseh2b(A174T/A174T)knock-in mice as a subclinical model of disease, identifying significant interferon-stimulated gene (ISG) transcript upregulation that recapitulates theISGsignature seen inAGSpatients. The inflammatory response is dependent on the nucleic acid sensor cyclicGMP-AMPsynthase (cGAS) and its adaptorSTINGand is associated with reduced cellular ribonucleotide excision repair activity and increasedDNAdamage. This suggests thatcGAS/STINGis a key nucleic acid-sensing pathway relevant toAGS, providing additional insight into disease pathogenesis relevant to the development of therapeutics for this childhood-onset interferonopathy and adult systemic autoimmune disorders.
Assuntos
Doenças Autoimunes do Sistema Nervoso/genética , Imunidade Inata/genética , Proteínas de Membrana/imunologia , Mutação de Sentido Incorreto , Malformações do Sistema Nervoso/genética , Nucleotidiltransferases/imunologia , Ribonuclease H/genética , Ribonucleases/genética , Animais , Doenças Autoimunes do Sistema Nervoso/imunologia , Doenças Autoimunes do Sistema Nervoso/metabolismo , Autoimunidade/genética , Dano ao DNA , Regulação da Expressão Gênica , Humanos , Interferons/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Malformações do Sistema Nervoso/imunologia , Malformações do Sistema Nervoso/metabolismo , Nucleotidiltransferases/genética , Nucleotidiltransferases/metabolismo , Ribonuclease H/metabolismoRESUMO
Cellular senescence is triggered by diverse stimuli and is characterized by long-term growth arrest and secretion of cytokines and chemokines (termed the SASP-senescence-associated secretory phenotype). Senescence can be organismally beneficial as it can prevent the propagation of damaged or mutated clones and stimulate their clearance by immune cells. However, it has recently become clear that senescence also contributes to the pathophysiology of aging through the accumulation of damaged cells within tissues. Here, we describe that inhibition of the reaction catalysed by LSG1, a GTPase involved in the biogenesis of the 60S ribosomal subunit, leads to a robust induction of cellular senescence. Perhaps surprisingly, this was not due to ribosome depletion or translational insufficiency, but rather through perturbation of endoplasmic reticulum homeostasis and a dramatic upregulation of the cholesterol biosynthesis pathway. The underlying transcriptomic signature is shared with several other forms of senescence, and the cholesterol biosynthesis genes contribute to the cell cycle arrest in oncogene-induced senescence. Furthermore, targeting of LSG1 resulted in amplification of the cholesterol/ER signature and restoration of a robust cellular senescence response in transformed cells, suggesting potential therapeutic uses of LSG1 inhibition.
Assuntos
Senescência Celular/genética , Estresse do Retículo Endoplasmático/genética , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Subunidades Ribossômicas Maiores de Eucariotos/metabolismo , Pontos de Checagem do Ciclo Celular/genética , Colesterol/biossíntese , Retículo Endoplasmático/metabolismo , Fibroblastos/metabolismo , Técnicas de Silenciamento de Genes , Células HEK293 , Homeostase/genética , Humanos , Biossíntese de Proteínas/genética , RNA Interferente Pequeno/genética , Proteínas de Ligação a RNA/antagonistas & inibidores , Proteínas de Ligação a RNA/metabolismo , Transcriptoma , Transfecção , Proteína Supressora de Tumor p53/metabolismoRESUMO
Hundreds of putative enzymes from Mycobacterium tuberculosis as well as other mycobacteria remain categorized as "conserved hypothetical proteins" or "hypothetical proteins", offering little or no information on their functional role in pathogenic and non-pathogenic processes. In this study we have predicted the fold and 3-D structure of more than 99% of all proteins encoded in the genome of M. tuberculosis H37Rv. Fold-recognition, database search, 3-D modelling was performed using Protein Homology/analogy Recognition Engine V 2.0 (Phyre2). These results are used to tentatively assign potential function for unannotated enzymes and proteins. In summary, fold-recognition and structural homology might be used as a complementary tool in genome annotation efforts and furthermore, it can deliver primary sequence-independent information regarding structure, ligands and even substrate specificity for enzymes that display low primary sequence identity with potential homologues in other species.