The let-7 miRNAwas one of the first miRNAs discovered in the nematode, Caenorhabditis elegans, and its biological functions show a high level of evolutionary conservation from the nematode to the human. Unlike in C. e...The let-7 miRNAwas one of the first miRNAs discovered in the nematode, Caenorhabditis elegans, and its biological functions show a high level of evolutionary conservation from the nematode to the human. Unlike in C. elegans, higher animals have multiple isoforms of let-7 miRNAs; these isoforms share a consensus sequence called the ＇seed sequence＇ and these isoforms are categorized into let-7 miRNA family. The expression of let-7 family is required for developmental timing and tumor suppressor function, but must be suppressed for the self-renewal of stem cells. Therefore, let-7 miRNA biogenesis must be carefully controlled. To generate a let-7 miRNA, a primary transcript is produced by RNA polymerase Ⅱ and then subsequently processed by Drosha/DGCR8, TUTase, and Dicer. Because dysregulation of let-7 processing is deleterious, biogenesis of let-7 is tightly regulated by cellular factors, such as the RNA binding proteins, LIN28A/B and DIS3L2. In this review, we discuss the biological functions and biogenesis of let-7 miRNAs, focusing on the molecular mechanisms of regulation of let-7 biogenesis in ver- tebrates, such as the mouse and the human.展开更多
文摘目的在大规模表达谱芯片中寻找与胰腺导管腺癌(PDAC)相关的RNA分子,并探讨其分子机制。方法基于RNA的表达谱数据,构建"转录因子-miRNA-mRNA"调控关系网络,挖掘与PDAC相关的mRNA及miRNA。结果 6个miR let-7家族miRNA成员(hsa-let-7i、hsa-let-7d、hsa-let-7b、hsa-let-7g、hsa-let-7c、hsa-let-7e)参与一个核心调控网络,其网络中涉及的基因和其他miRNA均为与PDAC发生发展相关的分子。其中处于网络核心位置的基因ALDH1A1、ZEB1、HMGA2、EGR1和TGFB1,与PDAC的发展及预后直接相关。网络中的hsa-mir-200b、hsa-mir-200a可与ZEB1基因相互调控,通过Notch信号通路影响PDAC的发展及转移。结论 miR let-7家族miRNA分子可能与ALDH1A1、ZEB1与HMGA2等分子相互调控,并与PDAC的发生发展密切相关。
文摘The let-7 miRNAwas one of the first miRNAs discovered in the nematode, Caenorhabditis elegans, and its biological functions show a high level of evolutionary conservation from the nematode to the human. Unlike in C. elegans, higher animals have multiple isoforms of let-7 miRNAs; these isoforms share a consensus sequence called the ＇seed sequence＇ and these isoforms are categorized into let-7 miRNA family. The expression of let-7 family is required for developmental timing and tumor suppressor function, but must be suppressed for the self-renewal of stem cells. Therefore, let-7 miRNA biogenesis must be carefully controlled. To generate a let-7 miRNA, a primary transcript is produced by RNA polymerase Ⅱ and then subsequently processed by Drosha/DGCR8, TUTase, and Dicer. Because dysregulation of let-7 processing is deleterious, biogenesis of let-7 is tightly regulated by cellular factors, such as the RNA binding proteins, LIN28A/B and DIS3L2. In this review, we discuss the biological functions and biogenesis of let-7 miRNAs, focusing on the molecular mechanisms of regulation of let-7 biogenesis in ver- tebrates, such as the mouse and the human.
