Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
Division of Gastroenterology and Hepatology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
Cell Death Dis. 2019 Feb 18;10(3):168. doi: 10.1038/s41419-019-1423-6.
Cholestasis induces the hepatic long non-coding RNA H19, which promotes the progression of cholestatic liver fibrosis. However, microRNAs that are dysregulated by H19 during cholestasis remain elusive. Using miRNA-sequencing analysis followed by qPCR validation, we identified marked upregulation of eight members of the let-7 family in cholestatic livers by bile duct ligation (BDL) and H19 overexpression. In particular, the expression of let-7a-1/7d/7f-1 was highly induced in H19-BDL livers but decreased in H19KO-BDL livers. Interestingly, H19 decreased the nuclear let-7 precursors as well as the primary transcripts of let-7a-1/7d/7f-1 levels in BDL mouse livers. Bioinformatics, RNA pull-down, and RNA immunoprecipitation (RIP) assays revealed that the crucial RNA-binding protein polypyrimidine tract-binding protein 1 (PTBP1), an H19 interaction partner, interacted with the precursors of let-7a-1 and let-7d and suppressed their maturation. Both PTBP1 and let-7 expression was differentially regulated by different bile acid species in hepatocyte and cholangiocyte cells. Further, H19 negatively regulated PTBP1's mRNA and protein levels but did not affect its subcellular distribution in BDL mouse livers. Moreover, we found that H19 restrained but PTBP1 facilitated the bioavailability of let-7 miRNAs to their targets. Taken together, this study revealed for the first time that H19 promoted let-7 expression by decreasing PTBP1's expression level and its binding to the let-7 precursors in cholestasis.
胆淤积诱导肝长链非编码 RNA H19，促进胆淤积性肝纤维化的进展。然而，胆淤积时 H19 调控的失调 microRNA 仍不清楚。通过 miRNA 测序分析和 qPCR 验证，我们发现胆管结扎（BDL）和 H19 过表达后，胆淤积肝脏中 let-7 家族的 8 个成员明显上调。特别是 let-7a-1/7d/7f-1 的表达在 H19-BDL 肝脏中高度诱导，但在 H19KO-BDL 肝脏中降低。有趣的是，H19 降低了核 let-7 前体以及 let-7a-1/7d/7f-1 的初级转录物在 BDL 小鼠肝脏中的水平。生物信息学、RNA 下拉和 RNA 免疫沉淀（RIP）试验表明，关键 RNA 结合蛋白多嘧啶 tract 结合蛋白 1（PTBP1）是 H19 的相互作用伙伴，与 let-7a-1 和 let-7d 的前体相互作用并抑制其成熟。PTBP1 和 let-7 的表达均受不同胆汁酸在肝细胞和胆管细胞中的差异调节。此外，H19 负调控 PTBP1 的 mRNA 和蛋白水平，但在 BDL 小鼠肝脏中不影响其亚细胞分布。此外，我们发现 H19 抑制但 PTBP1 促进 let-7 miRNAs 对其靶标的生物利用度。总之，本研究首次揭示了 H19 通过降低 PTBP1 的表达水平及其与 let-7 前体的结合，促进胆淤积时 let-7 的表达。
