Ubiquitin-like posttranslational modifications in NAFLD progression and treatment

Nonalcoholic fatty liver disease(NAFLD)is a long-lasting condition that affects the liver,destroying its function.Liver injury can cause steatosis and inflammation,and further activation of hepatic stellate cells(HSCs)often leads to the development of nonalcoholic liver fibrosis.The patient with NAFLD is at risk of developing advanced liver disease and complications,such as liver failure,hepatocellular carcinoma(HCC),and portal hypertension.Although our understanding of the cellular and molecular mechanisms of NAFLD has greatly improved in recent years,treatment remains limited.Analysis and characterization of protein posttranslational modifications(PTMs)could improve our understanding of NAFLD pathology and leading to the development of new and more effective treatments.In recent years,a number of studies have described how ubiquitin-like(Ubl)-PTMs change during NAFLD and how treatments targeting specific enzymes mediating these Ubl-PTMs can improve various liver diseases,particularly in relation to NAFLD and nonalcoholic liver fibrosis.New strategies for evaluating modified proteomes could provide novel insights into the roles of Ubl-PTMs in NAFLD progression and the therapeutic value of targeting the proteins involved in these Ubl-PTMs.

Regulatory factor X5 promotes hepatocellular carcinoma progression by transactivating tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein theta and suppressing apoptosis

Background:Our previous studies have shown that regulatory factor X5(RFX5),a classical transcription regulator of MHCⅡ genes,was obviously overexpressed in hepatocellular carcinoma(HCC)tumors.However,the role of RFX5 in the carcinogenesis and progress of HCC remains unknown.This study aimed to reveal its biological significance and the underlying mechanism in HCC.Methods:RFX5 mRNA expression level and copy number variation in HCC tumors and cell lines were determined by analyzing deposited data sets in the Cancer Genome Atlas and Gene Expression Omnibus database.The biological significance of RFX5 in HCC was investigated by monitoring the colony formation and subcutaneous tumor growth capacity when RFX5 was silenced with lentiviral short hairpin RNA and CRISPR7Cas9 system in HCC cell lines.The downstream gene transcriptionally activated by RFX5 in HCC cells was determined by chromatin immunoprecipitation and luciferase reporter assay.The involvement of tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein theta(YWHAQ)in HCC development was further determined by performing colony formation rescue assay and subcutaneous tumor growth rescue experiment.The association of YWHAQ with recurrence-free survival of patients with HCC was assessed by Kaplan-Meier analysis.Moreover,apoptosis level and the protein level of p53 pathway were determined to reveal the mechanism of RFX5 in driving HCC development.Results:RFX5 was amplified and highly overexpressed in HCC tumor tissues compared with the corresponding non-tumor tissues.The mRNA expression level of RFX5 was significantly correlated with its DNA copy number(r=0.4,P<0.001).Functional study demonstrated that RFX5 was required for both clonogenic forming in vitro and subcutaneous tumor growth in vivo of HCC cells.Further study identified YWHAQ,namely 14-3-3 tau,as a key downstream transcriptional target gene of RFX5,which was tightly regulated by RFX5 in HCC.Moreover,overexpression of YWHAQ largely rescued the clonogenic growth of HCC cells that was suppressed by RFX5 knockdown.In addition,overexpression of YWHAQ in primary tumor was linked to poor prognosis of patients with HCC.These results demonstrated that YWHAQ was a downstream effector of RFX5 in HCC.Notably,RFX5-YWHAQ pathway could protect cells from apoptosis by suppressing the p53 and Bax in HCC.Conclusion:RFX5 is a putative HCC driver gene that plays an important role in the development and progression of HCC by transactivating YWHAQ and suppressing apoptosis.