Mesh : Binding Sites Carcinoma, Hepatocellular / genetics metabolism Cell Line, Tumor Chromatin / chemistry Cyclic AMP Response Element-Binding Protein / metabolism Cyclic AMP-Dependent Protein Kinase Catalytic Subunits / genetics Cyclic AMP-Dependent Protein Kinases / metabolism Gene Expression Regulation, Neoplastic Histones / metabolism Humans Liver Neoplasms / genetics metabolism MicroRNAs / metabolism Promoter Regions, Genetic RNA, Untranslated / biosynthesis genetics Transcription Factors / metabolism Transcription Initiation Site Transcription, Genetic Transcriptional Activation Up-Regulation

来  源:   DOI:10.1093/nar/gkq285   PDF(Pubmed)

Abstract:
Long non-coding RNA (lncRNA), highly up-regulated in liver cancer (HULC) plays an important role in tumorigenesis. Depletion of HULC resulted in a significant deregulation of several genes involved in liver cancer. Although up-regulation of HULC expression in hepatocellular carcinoma has been reported, the molecular mechanisms remain unknown. In this study, we used in vivo and in vitro approaches to characterize cancer-dependent alterations in the chromatin organization and find a CREB binding site (encompassing from -67 to -53 nt) in the core promoter. Besides, we also provided evidence that PKA pathway may involved in up-regulation of HULC. Furthermore, we demonstrated HULC may act as an endogenous \'sponge\', which down-regulates a series of microRNAs (miRNAs) activities, including miR-372. Inhibition of miR-372 leads to reducing translational repression of its target gene, PRKACB, which in turn induces phosphorylation of CREB. Over-expression of miR-372 decreases the association of CREB with the proximal promoter, followed by the dissociation of P300, resulting in a change of the histone \'code\', such as in deacetylation and methylation. The study elucidates that fine tuning of HULC expression is part of an auto-regulatory loop in which it\'s inhibitory to expression and activity of miR-372 allows lncRNA up-regulated expression in liver cancer.
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