RP11-40C6.2 Inactivates Hippo Signaling by Attenuating YAP1 Ubiquitylation in Hepatitis B Virus-associated Hepatocellular Carcinoma

Background and Aims: Chronic hepatitis caused by hepatitis B virus (HBV) infection is a leading cause of hepatocellular carcinoma (HCC). We investigated the roles of oncogenic HBV infection-associated long noncoding RNAs in HCC. Methods: Bioinformatics analysis of data from the Cancer Genome Atlas (TCGA) was performed to screen potential oncogenic HBV-related lncRNAs. Next, we assessed their expression in clinical samples and investigated their correlation with clinical characteristics. The detailed oncogenic effects were analyzed by performing in vitro and in vivo studies. Results: RP11-40C6.2, an HBV infection-related lncRNA, was identified by analysis of the TCGA-Liver Hepatocellular Carcinoma database. Gene Set Enrichment Analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of differentially expressed genes revealed a strong association of RP11-40C6.2 with the Hippo signaling pathway. RP11-40C6.2 was overexpressed in HCC patients with HBV infection compared to those without HBV infection. RP11-40C6.2 transcription showed a positive association with HBV-X protein (HBx), but not HBV core protein (HBc) expression, both of which are carcinogenic proteins. Luciferase gene reporter and ChIP assays revealed that YAP1/TAZ/TEADs complex enhanced RP11-40C6.2 transcription by binding to its promoter area. RP11-40C6.2 showed oncogenic characteristics in HCC cell lines and in animal models that were mediated via activation of YAP1. In vitro ubiquitylation assay revealed that RP11-40C6.2 can promote the stabilization of YAP1 by stopping phosphorylation at its s127 residue and further stopping its degradation through binding to 14-3-3. Conclusions: RP11-40C6.2 is an HBV infection-related lncRNA that exerts its oncogenic effects by targeting the Hippo signaling pathway.