The regulation of miR-122 which is involved in Hepatitis C virus replication and interferon treatment response

Mir-122是一种高度丰富的肝脏特异性miRNA，据报道可增强丙型肝炎病毒（HCV）的复制，并与干扰素治疗反应和肝癌发生有关。在本研究中，我们研究了miR-122的调控机制。首先，我们通过real - time PCR检测了miR-122在各种肝癌细胞系中的表达水平与miR-122的主要转录物pri-miR-122的相关性。结果显示miR-122与pri-miR-122呈正相关。因此，pri-miR-122的表达水平被认为是决定miR-122表达水平的主要因素。接下来，我们在pri-miR-122启动子中进行了整合截断的报告基因检测，并确定了具有高反式激活效应的区域。接下来，我们通过亚硫酸氢钠DNA测序检测了pri-miR-122启动子区域的DNA甲基化状态，发现在pri-miR-122低表达的肝癌细胞系中，pri-miR-122的启动子区域发生了超甲基化。此外，在5-aza-CdR处理下，pri-miR-122在这些细胞系中的表达水平升高。因此，表观遗传调控可能在miR-122的表达中发挥重要作用。

Mir-122 is a highly abundant and liver-specific miRNA, and reported to enhance Hepatitis C virus (HCV) replication and be associated with interferon treatment response and hepatocarcinogenesis. In this study, we investigated the regulation mechanism of miR-122. At first, we examined the correlation between the expression level of miR-122 and pri-miR-122 which was primary transcript of miR-122 in various hepatoma cell lines by realtime PCR. The result showed the positive correlation between miR-122 and pri-miR-122. Therefore, the expression level of pri-miR-122 was considered to be a major factor which determined that of miR-122. Next, we performed reporter gene assays integrated with truncation in the pri-miR-122 promoter, and determined the region which had high trans-activation effect. Next, we examined the DNA methylation status in the promoter region of pri-miR-122 by sodium bisulfite DNA sequencing, and found that the promoter region of pri-miR-122 was hyper-methylated in the hepatoma cell lines which have the low expression level of pri-miR-122. Moreover, with 5-aza-CdR treatment, the expression level of pri-miR-122 was increased in such cell lines. Therefore, the epigenetic regulation might play an important role in the expression of miR-122.