University of Iowa School of Medicine, Department of Internal Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
Am J Physiol Gastrointest Liver Physiol. 2010 Apr;298(4):G535-41. doi: 10.1152/ajpgi.00338.2009. Epub 2010 Feb 18.
During liver regeneration, normally quiescent liver cells reenter the cell cycle, nonparenchymal and parenchymal cells divide, and proper liver architecture is restored. The gene expression programs regulating these transitions are not completely understood. MicroRNAs are a newly discovered class of small regulatory RNAs that silence messenger RNAs by binding to their 3'-untranslated regions (UTRs). A number of microRNAs, including miR-21, have been shown to be involved in regulation of cell proliferation. We performed partial hepatectomies on mice and allowed the liver to regenerate for 1, 6, 12, 24, and 48 h and 4 and 7 days. We compared the expression of miR-21 in the posthepatectomy liver to the prehepatectomy liver by Northern blot and found that miR-21 was upregulated during the early stages of liver regeneration. NF-kappaB signaling is also activated very early during liver regeneration. It has been previously reported that NF-kappaB upregulates the miR-21 precursor transcript. The predicted miR-21 target, Pellino (Peli1), is a ubiquitin ligase involved in activating NF-kappaB signaling. We observed an inverse correlation between miR-21 and Peli1 mRNA levels during liver regeneration. miR-21 overexpression in cultured cells inhibited a Peli1 3'-UTR luciferase reporter. Using NF-kappaB reporter assays, we determined that miR-21 overexpression inhibits NF-kappaB signaling. In conclusion, miR-21 expression was upregulated during early stages of liver regeneration. Targeting of Peli1 by miR-21 could potentially provide the basis for a negative feedback cycle regulating NF-kappaB signaling.
在肝脏再生过程中，通常处于静止状态的肝细胞重新进入细胞周期，非实质细胞和实质细胞分裂，适当的肝脏结构得以恢复。调节这些转变的基因表达程序尚未完全了解。microRNAs 是一类新发现的小调控 RNA，通过与信使 RNA 的 3'非翻译区 (UTR) 结合来沉默信使 RNA。已经有许多 microRNAs，包括 miR-21，被证明参与了细胞增殖的调控。我们对小鼠进行部分肝切除术，让肝脏再生 1、6、12、24 和 48 小时以及 4 和 7 天。我们通过 Northern blot 比较了肝切除术后肝脏中 miR-21 的表达与肝切除术前的表达，发现 miR-21 在肝脏再生的早期阶段上调。NF-kappaB 信号也在肝脏再生的早期非常活跃地被激活。先前有报道称 NF-kappaB 上调了 miR-21 前体转录本。预测的 miR-21 靶标，Pellino (Peli1)，是一种参与激活 NF-kappaB 信号的泛素连接酶。我们观察到在肝脏再生过程中 miR-21 和 Peli1 mRNA 水平之间存在负相关。培养细胞中的 miR-21 过表达抑制了 Peli1 3'UTR 荧光素酶报告基因。通过 NF-kappaB 报告基因检测，我们确定 miR-21 过表达抑制了 NF-kappaB 信号。总之，miR-21 在肝脏再生的早期阶段上调。miR-21 对 Peli1 的靶向作用可能为调节 NF-kappaB 信号的负反馈循环提供基础。
