Long non-coding RNA TUG1 regulates multiple glycolytic enzymes in hepatocellular carcinoma cells via sponging microRNA-122-5p
Hepatocellular carcinoma (HCC) remains the third leading cause of cancer deaths; however, its therapeutic options are limited. Understanding the molecular mechanisms of HCC could shed light on new therapies. Emerging studies indicate the important role of long-noncoding RNAs (lncRNAs) in the pathogenesis of HCC. One of the early discovered lncRNAs, taurine-upregulated gene 1 (TUG1), has been up-regulated in HCC tissues, but its impact on HCC cells' transcriptomics remains unexplored. We established TUG1-knockdown HCC cells and performed RNA-seq analysis. KEGG analysis revealed the significant enrichment of downregulated genes involved in glycolysis. Accordingly, TUG1-depleted HCC cells showed impairments in glucose uptake, ATP synthesis, and lactate production. Clinical HCC tissue data revealed positive gene expression correlations between TUG1 and glycolysis genes identified by RNA-seq. To identify a molecular function of TUG1 in glycolysis, we explored the competing endogenous (ceRNA) model and identified five microRNAs (miRNAs) with the highest number of TUG1 binding sites using bioinformatic tools. Amongst these miRNAs, microRNA-122-5p (miR-122-5p) displayed an inverse relationship for gene expression with most TUG1-regulated glycolysis genes, including PKM, ALDOA, ENO2, and PFKM. Dual luciferase assays confirmed the direct interaction between TUG1 and miR-122-5p and between miR-122-5p and the 3' untranslated regions (3'UTR) of PKM and ALDOA. We further showed that inhibition of miR-122-5p alleviated the suppression of glycolysis induced by TUG1 depletion. Together, our RNA-seq analysis of TUG1-depleted HCC cells in combination with clinical data reveals the crucial function of TUG1 in promoting glycolysis via sponging miR-122-5p, which is a negative regulator of multiple glycolytic enzymes. Overall design: To investigate the influence and the molecular function of  lncRNA TUG1 on biological pathway in HCC cell lines, we established TUG1-knockdown HepG2 lines with shRNA.  Three technical replicated were performed for each group (shCon,  sh1-TUG1, and sh2-TUG1) to obtaine the expression profile followed by trascriptomic analysis.