RESUMO
There are still gaps in our understanding of the complex processes by which p53 suppresses tumorigenesis. Here we describe a novel role for p53 in suppressing the mevalonate pathway, which is responsible for biosynthesis of cholesterol and nonsterol isoprenoids. p53 blocks activation of SREBP-2, the master transcriptional regulator of this pathway, by transcriptionally inducing the ABCA1 cholesterol transporter gene. A mouse model of liver cancer reveals that downregulation of mevalonate pathway gene expression by p53 occurs in premalignant hepatocytes, when p53 is needed to actively suppress tumorigenesis. Furthermore, pharmacological or RNAi inhibition of the mevalonate pathway restricts the development of murine hepatocellular carcinomas driven by p53 loss. Like p53 loss, ablation of ABCA1 promotes murine liver tumorigenesis and is associated with increased SREBP-2 maturation. Our findings demonstrate that repression of the mevalonate pathway is a crucial component of p53-mediated liver tumor suppression and outline the mechanism by which this occurs.
Assuntos
Ácido Mevalônico/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Transportador 1 de Cassete de Ligação de ATP/metabolismo , Animais , Linhagem Celular , Colesterol/metabolismo , Feminino , Genes Supressores de Tumor , Células HCT116 , Hepatócitos/metabolismo , Humanos , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neoplasias/genética , Regiões Promotoras Genéticas , Proteína de Ligação a Elemento Regulador de Esterol 2/metabolismo , Terpenos/metabolismoRESUMO
Although TP53 is the most commonly mutated gene in human cancers, the p53-dependent transcriptional programs mediating tumor suppression remain incompletely understood. Here, to uncover critical components downstream of p53 in tumor suppression, we perform unbiased RNAi and CRISPR-Cas9-based genetic screens in vivo. These screens converge upon the p53-inducible gene Zmat3, encoding an RNA-binding protein, and we demonstrate that ZMAT3 is an important tumor suppressor downstream of p53 in mouse KrasG12D-driven lung and liver cancers and human carcinomas. Integrative analysis of the ZMAT3 RNA-binding landscape and transcriptomic profiling reveals that ZMAT3 directly modulates exon inclusion in transcripts encoding proteins of diverse functions, including the p53 inhibitors MDM4 and MDM2, splicing regulators, and components of varied cellular processes. Interestingly, these exons are enriched in NMD signals, and, accordingly, ZMAT3 broadly affects target transcript stability. Collectively, these studies reveal ZMAT3 as a novel RNA-splicing and homeostasis regulator and a key component of p53-mediated tumor suppression.
Assuntos
Proteínas de Ligação a RNA/genética , Proteína Supressora de Tumor p53/genética , Adenocarcinoma/genética , Processamento Alternativo , Animais , Proteínas de Ciclo Celular/metabolismo , Éxons , Perfilação da Expressão Gênica/métodos , Genes Supressores de Tumor , Humanos , Neoplasias Hepáticas/genética , Masculino , Camundongos , Camundongos Endogâmicos ICR , Camundongos SCID , Interferência de RNA , Splicing de RNA , Proteínas de Ligação a RNA/metabolismo , Proteína Supressora de Tumor p53/metabolismoRESUMO
A segmental deletion resulting in DNAJB1-PRKACA gene fusion is now recognized as the signature genetic event of fibrolamellar hepatocellular carcinoma (FL-HCC), a rare but lethal liver cancer that primarily affects adolescents and young adults. Here we implement CRISPR-Cas9 genome editing and transposon-mediated somatic gene transfer to demonstrate that expression of either the endogenous fusion protein or a chimeric cDNA leads to the formation of indolent liver tumors in mice that closely resemble human FL-HCC. Notably, overexpression of the wild-type PRKACA was unable to fully recapitulate the oncogenic activity of DNAJB1-PRKACA, implying that FL-HCC does not simply result from enhanced PRKACA expression. Tumorigenesis was significantly enhanced by genetic activation of ß-catenin, an observation supported by evidence of recurrent Wnt pathway mutations in human FL-HCC, as well as treatment with the hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine, which causes tissue injury, inflammation, and fibrosis. Our study validates the DNAJB1-PRKACA fusion kinase as an oncogenic driver and candidate drug target for FL-HCC, and establishes a practical model for preclinical studies to identify strategies to treat this disease.
Assuntos
Carcinoma Hepatocelular/genética , Subunidades Catalíticas da Proteína Quinase Dependente de AMP Cíclico/genética , Proteínas de Choque Térmico HSP40/genética , Neoplasias Hepáticas Experimentais/genética , Neoplasias Hepáticas/genética , Regeneração Hepática/genética , Fígado/fisiologia , Proteínas de Fusão Oncogênica/genética , beta Catenina/genética , Adulto , Animais , Sequência de Bases , Carcinogênese/induzido quimicamente , Carcinogênese/genética , Carcinoma Hepatocelular/patologia , Cromossomos Humanos Par 19/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Estudos de Coortes , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Fígado/efeitos dos fármacos , Fígado/patologia , Neoplasias Hepáticas/patologia , Neoplasias Hepáticas Experimentais/induzido quimicamente , Camundongos , Camundongos Endogâmicos C57BL , Piridinas/toxicidade , Deleção de Sequência/genética , Adulto JovemRESUMO
PI5P4Ks are a class of phosphoinositide kinases that phosphorylate PI-5-P to PI-4,5-P2. Distinct localization of phosphoinositides is fundamental for a multitude of cellular functions. Here, we identify a role for peroxisomal PI-4,5-P2 generated by the PI5P4Ks in maintaining energy balance. We demonstrate that PI-4,5-P2 regulates peroxisomal fatty acid oxidation by mediating trafficking of lipid droplets to peroxisomes, which is essential for sustaining mitochondrial metabolism. Using fluorescent-tagged lipids and metabolite tracing, we show that loss of the PI5P4Ks significantly impairs lipid uptake and ß-oxidation in the mitochondria. Further, loss of PI5P4Ks results in dramatic alterations in mitochondrial structural and functional integrity, which under nutrient deprivation is further exacerbated, causing cell death. Notably, inhibition of the PI5P4Ks in cancer cells and mouse tumor models leads to decreased cell viability and tumor growth, respectively. Together, these studies reveal an unexplored role for PI5P4Ks in preserving metabolic homeostasis, which is necessary for tumorigenesis.
Assuntos
Carcinogênese/genética , Mitocôndrias/genética , Neoplasias/metabolismo , Peroxissomos/metabolismo , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Animais , Linhagem Celular Tumoral , Metabolismo Energético/genética , Feminino , Homeostase/genética , Humanos , Gotículas Lipídicas/metabolismo , Metabolismo dos Lipídeos/genética , Masculino , Camundongos , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Neoplasias/genética , Neoplasias/patologia , Peroxissomos/genéticaRESUMO
Neuronal fate-restricted intermediate progenitors (IPs) are derived from the multipotent radial glia (RGs) and serve as the direct precursors for cerebral cortical neurons, but factors that control their neurogenic plasticity remain elusive. Here we report that IPs' neuron production is enhanced by abrogating filamin function, leading to the generation of periventricular neurons independent of normal neocortical neurogenesis and neuronal migration. Loss of Flna in neural progenitor cells (NPCs) led RGs to undergo changes resembling epithelial-mesenchymal transition (EMT) along with exuberant angiogenesis that together changed the microenvironment and increased neurogenesis of IPs. We show that by collaborating with ß-arrestin, Flna maintains the homeostatic signaling between the vasculature and NPCs, and loss of this function results in escalated Vegfa and Igf2 signaling, which exacerbates both EMT and angiogenesis to further potentiate IPs' neurogenesis. These results suggest that the neurogenic potential of IPs may be boosted in vivo by manipulating Flna-mediated neurovascular communication.
Assuntos
Filaminas/metabolismo , Neurogênese , Neuroglia/fisiologia , Células-Tronco/fisiologia , Regulação para Cima , Animais , Filaminas/deficiência , Camundongos , Camundongos Knockout , Neovascularização FisiológicaRESUMO
Successfully completing the S phase of each cell cycle ensures genome integrity. Impediment of DNA replication can lead to DNA damage and genomic disorders. In this study, we show a novel function for NDE1, whose mutations cause brain developmental disorders, in safeguarding the genome through S phase during early steps of neural progenitor fate restrictive differentiation. Nde1 mutant neural progenitors showed catastrophic DNA double strand breaks concurrent with the DNA replication. This evoked DNA damage responses, led to the activation of p53-dependent apoptosis, and resulted in the reduction of neurons in cortical layer II/III. We discovered a nuclear pool of Nde1, identified the interaction of Nde1 with cohesin and its associated chromatin remodeler, and showed that stalled DNA replication in Nde1 mutants specifically occurred in mid-late S phase at heterochromatin domains. These findings suggest that NDE1-mediated heterochromatin replication is indispensible for neuronal differentiation, and that the loss of NDE1 function may lead to genomic neurological disorders.