■细胞转录组的稳态取决于转录和剪接机制。此外,基因表达的保真度,通过不同的质量控制机制,包括无义介导的RNA衰变(NMD),可以确保保持细胞身份和功能。在这种情况下,交替拼接耦合到NMD,已知导致异常基因同种型积累的这些机制中的一些改变与包括癌症在内的人类疾病有关。
■RNA测序,西方印迹,在多个沉默的培养细胞系(重复n≥4)中进行qPCR和免疫共沉淀,原代肝细胞和动物模型样本(Jo2,APAP,Mdr2-/-小鼠,n≥3)。
■在这里,我们表明在肝损伤的动物模型和人类肝癌(TCGA,非肿瘤=50vs.HCC=374),NMD的进程受到抑制。此外,我们证明剪接因子SLU7与NMD效应子UPF1相互作用并保留其水平,并且SLU7是正确的NMD所必需的。我们先前的发现表明,SLU7在患病的肝脏中表达减少,在疾病进展过程中导致肝细胞去分化和基因组不稳定。在这里,我们通过提供在肝损伤期间激活的胱天蛋白酶负责SLU7的裂解和降解的证据来建立这一点。
■在这里,我们将UPF1的下调和NMD的抑制确定为有助于肝脏转录组恶性重塑的新分子途径。此外,而且重要的是,我们发现caspase激活是肝脏疾病进展过程中SLU7表达下调的机制,这是细胞凋亡与肝癌发生之间的新联系。
■涉及重塑肝细胞转录组,从而驱动肝脏疾病中细胞身份和功能的进行性丧失的机制尚未完全了解。在这种情况下,我们提供了一个关键的mRNA监测机制受损的证据,该机制被称为无义介导的mRNA衰减(NMD).机械上,我们发现剪接因子SLU7在NMD调节中的新作用,包括其相互作用和保持关键NMD因子UPF1水平的能力。此外,我们证明,肝损伤过程中半胱天冬酶的激活介导SLU7和UPF1蛋白降解和NMD抑制。我们的发现确定了肝病进展的潜在新标志物,和SLU7作为新的治疗靶点,以防止慢性损伤器官的功能衰退。
UNASSIGNED: The homeostasis of the cellular transcriptome depends on transcription and splicing mechanisms. Moreover, the fidelity of gene expression, essential to preserve cellular identity and function is secured by different quality control mechanisms including nonsense-mediated RNA decay (NMD). In this context, alternative splicing is coupled to NMD, and several alterations in these mechanisms leading to the accumulation of aberrant gene isoforms are known to be involved in human disease including cancer.
UNASSIGNED: RNA sequencing, western blotting, qPCR and co-immunoprecipitation were performed in multiple silenced culture cell lines (replicates n ≥4), primary hepatocytes and samples of animal models (Jo2, APAP, Mdr2 -/- mice, n ≥3).
UNASSIGNED: Here we show that in animal models of liver injury and in human HCC (TCGA, non-tumoral = 50 vs. HCC = 374), the process of NMD is inhibited. Moreover, we demonstrate that the splicing factor SLU7 interacts with and preserves the levels of the NMD effector UPF1, and that SLU7 is required for correct NMD. Our previous findings demonstrated that SLU7 expression is reduced in the diseased liver, contributing to hepatocellular dedifferentiation and genome instability during disease progression. Here we build on this by providing evidence that caspases activated during liver damage are responsible for the cleavage and degradation of SLU7.
UNASSIGNED: Here we identify the downregulation of UPF1 and the inhibition of NMD as a new molecular pathway contributing to the malignant reshaping of the liver transcriptome. Moreover, and importantly, we uncover caspase activation as the mechanism responsible for the downregulation of SLU7 expression during liver disease progression, which is a new link between apoptosis and hepatocarcinogenesis.
UNASSIGNED: The mechanisms involved in reshaping the hepatocellular transcriptome and thereby driving the progressive loss of cell identity and function in liver disease are not completely understood. In this context, we provide evidence on the impairment of a key mRNA surveillance mechanism known as nonsense-mediated mRNA decay (NMD). Mechanistically, we uncover a novel role for the splicing factor SLU7 in the regulation of NMD, including its ability to interact and preserve the levels of the key NMD factor UPF1. Moreover, we demonstrate that the activation of caspases during liver damage mediates SLU7 and UPF1 protein degradation and NMD inhibition. Our findings identify potential new markers of liver disease progression, and SLU7 as a novel therapeutic target to prevent the functional decay of the chronically injured organ.