Expression of microRNA-195 is transactivated by Sp1 but inhibited by histone deacetylase 3 in hepatocellular carcinoma cells.
Expression of microRNA-195 is transactivated by Sp1 but inhibited by histone deacetylase 3 in hepatocellular carcinoma cells.
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DOI：
10.1016/j.bbagrm.2016.05.006
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发表时间：
2016-07
期刊：
影响因子：
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通讯作者：
Na Zhao;Siwen Li;Ruizhi Wang;Manhuan Xiao;Yu Meng;C. Zeng;Jian-Hong Fang;Jin-E Yang;
中科院分区：
文献类型：
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作者：
Na Zhao;Siwen Li;Ruizhi Wang;Manhuan Xiao;Yu Meng;C. Zeng;Jian-Hong Fang;Jin-E Yang;
MIR-195在各种癌症中的表达经常降低，但其潜在机制仍不清楚。为了探讨在肝细胞癌中miR-195基因表达下调是否与转录异常有关，我们将成熟miR-195基因上游的−2165bp片段定位为转录起始点，将−2.4至miR-195基因的2.0kb片段定位为miR-195基因的启动子。随后的研究表明，预测的Sp1结合位点的缺失降低了iR-195启动子的活性；Sp1沉默显著降低了iR-195启动子的活性和内源性miR-195的水平；Sp1在体内外直接与iR-195启动子相互作用。这些数据表明Sp1是iR-195转录的反式激活因子。有趣的是，miR-195的表达也受到表观遗传调控。组蛋白脱乙酰酶3(HDAC3)可通过与Sp1相互作用与iR-195启动子结合，从而通过去乙酰化组蛋白抑制Sp1介导的miR-195反式激活。在人肝癌组织中，HDAC3蛋白表达显著增加，且HDAC3上调与miR-195下调显著相关，提示HDAC3上调可能是肝细胞癌miR-195下调的重要原因。我们的发现揭示了在肝癌细胞中miR-195转录调控和表达解除调控的机制，并为癌细胞中microRNA的生物发生提供了新的见解。
MiR-195 expression is frequently reduced in various cancers, but its underlying mechanisms remain unknown. To explore whether abnormal transcription contributed to miR-195 downregulation in hepatocellular carcinoma (HCC), we characterized the −2165-bp site upstream of mature miR-195 as transcription start site and the −2.4 to −2.0-kb fragment as the promoter ofmiR-195gene. Subsequent investigation showed that deletion of the predicted Sp1 binding site decreased themiR-195promoter activity; Sp1 silencing significantly reduced themiR-195promoter activity and the endogenous miR-195 level; Sp1 directly interacted with themiR-195promoterin vitroandin vivo. These data suggest Sp1 as a transactivator formiR-195transcription. Interestingly,miR-195expression was also subjected to epigenetic regulation. Histone deacetylase 3 (HDAC3) could anchor to themiR-195promoterviainteracting with Sp1 and consequently repress the Sp1-mediated miR-195 transactivation by deacetylating histone in HCC cells. Consistently, substantial increase of HDAC3 protein was detected in human HCC tissues and HDAC3 upregulation was significantly correlated with miR-195 downregulation, suggesting that HDAC3 elevation may represent an important cause for miR-195 reduction in HCC. Our findings uncover the mechanisms underlying the transcriptional regulation and expression deregulation ofmiR-195in HCC cells and provide new insight into microRNA biogenesis in cancer cells.