Objective The HBV HBx regulatory protein is required for transcription from the covalently closed circular DNA (cccDNA) minichromosome and affects the epigenetic control of both viral and host cellular chromatin. Design We explored, in relevant cellular models of HBV replication, the functional consequences of HBx interaction with DLEU2, a long non-coding RNA (lncRNA) expressed in the liver and increased in human hepatocellular carcinoma (HCC), in the regulation of host target genes and the HBV cccDNA. Results We show that HBx binds the promoter region, enhances the transcription and induces the accumulation of DLEU2 in infected hepatocytes. We found that nuclear DLEU2 directly binds HBx and the histone methyltransferase enhancer of zeste homolog 2 (EZH2), the catalytic active subunit of the polycomb repressor complex 2 (PRC2) complex. Computational modelling and biochemical evidence suggest that HBx and EZH2 share two preferential binding sites in DLEU2 intron 1. HBx and DLEU2 co-recruitment on the cccDNA displaces EZH2 from the viral chromatin to boost transcription and viral replication. DLEU2-HBx association with target host promoters relieves EZH2 repression and leads to the transcriptional activation of a subset of EZH2/PRC2 target genes in HBV-infected cells and HBV-related HCCs. Conclusions Our results highlight the ability of HBx to bind RNA to impact on the epigenetic control of both viral cccDNA and host genes and provide a new key to understand the role of DLEU2 and EZH2 overexpression in HBV-related HCCs and HBx contribution to hepatocytes transformation.

The FUS gene has been linked to amyotrophic lateral sclerosis (ALS). FUS is a ubiquitous RNA-binding protein, and the mechanisms leading to selective motoneuron loss downstream of ALS-linked mutations are largely unknown. We report the transcriptome analysis of human purified motoneurons, obtained from FUS wild-type or mutant isogenic induced pluripotent stem cells (iPSCs). Gene ontology analysis of differentially expressed genes identified significant enrichment of pathways previously associated to sporadic ALS and other neurological diseases. Several microRNAs (miRNAs) were also deregulated in FUS mutant motoneurons, including miR-375, involved in motoneuron survival. We report that relevant targets of miR-375, including the neural RNA-binding protein ELAVL4 and apoptotic factors, are aberrantly increased in FUS mutant motoneurons. Characterization of transcriptome changes in the cell type primarily affected by the disease contributes to the definition of the pathogenic mechanisms of FUS-linked ALS.

Amyotrophic lateral sclerosis (ALS) has been genetically linked to mutations in RNA-binding proteins (RBPs), including FUS. Here, we report the RNA interactome of wild-type and mutant FUS in human motor neurons (MNs). This analysis identified a number of RNA targets. Whereas the wild-type protein preferentially binds introns, the ALS mutation causes a shift toward 3' UTRs. Neural ELAV-like RBPs are among mutant FUS targets. As a result, ELAVL4 protein levels are increased in mutant MNs. ELAVL4 and mutant FUS interact and co-localize in cytoplasmic speckles with altered biomechanical properties. Upon oxidative stress, ELAVL4 and mutant FUS are engaged in stress granules. In the spinal cord of FUS ALS patients, ELAVL4 represents a neural-specific component of FUS-positive cytoplasmic aggregates, whereas in sporadic patients it co-localizes with phosphorylated TDP-43-positive inclusions. We propose that pathological mutations in FUS trigger an aberrant crosstalk with ELAVL4 with implications for ALS.

The histone methyltransferase EZH2 as a druggable target in SHH medulloblastoma cancer stem cells The histone methyltransferase EZH2 as a druggable target in SHH medulloblastoma cancer stem cells

The long noncoding RNA linc-NeD125 controls the expression of medulloblastoma driver genes by microRNA sponge activity The long noncoding RNA linc-NeD125 controls the expression of medulloblastoma driver genes by microRNA sponge activity

IDO1 involvement in mTOR pathway: A molecular mechanism of resistance to mTOR targeting in medulloblastoma