The let-7 Regulatory Network

 描述(由申请人提供) RNA干扰(RNAi)在动植物基因表达的发育、转录后调控中发挥着重要作用，并可影响基因组结构和染色质结构。虽然许多研究都集中在识别microRNA(MiRNA)靶标和基因沉默的各种下游机制上，但这里我们感兴趣的是特定miRNA let-7的调控。多能性因子Lin28抑制哺乳动物microRNAs let-7家族的生物发生。LIN28在胚胎干细胞中高表达，在发育、葡萄糖代谢和组织再生中起着重要的调节作用。另一种选择是，Lin28的过度表达与多种癌症的发生有关，而肿瘤抑制因子let-7可以沉默几个人类癌基因。Lin28/let-7通路就像一个双稳开关。每个分子抑制另一个分子的表达，一旦细胞改变其状态，结果就是分化，或者如果开关逆转，就会导致癌症。在分子L e e L，LIN28与前体let-7(Pre-let-7)发夹结合，触发3‘寡核苷酸活性。 TUT4和/或TUT7。添加到Pre-let-7的寡核苷酸尾巴作为衰变信号，因为它被核酸外切酶Dis3l2迅速降解。在体细胞中，在缺少L的情况下，TUT4/7通过催化单个尿苷与一组Pre-let-7miRNAs的加成来促进let-7的生物发生。在这里，我们建议研究Lin28介导的TUT4/7向Prelet-7募集的分子基础，在没有Lin28的情况下TUT4/7活性在没有Lin28的情况下从单尿苷酸酶到有Lin28的寡苷酸酶之间的切换，以及随后Dis312对Prelet-7的降解。我们将利用类似的方法来开始了解TUT4/7在用非模板尿氨酸标记miRNA和mRNA时所扮演的更广泛的角色。

 DESCRIPTION (provided by applicant) RNA interference (RNAi) plays an important role in development, post-transcriptional regulation of gene expression in plants and animals and can impact genome organization and chromatin structure. While many studies focus on the identification of microRNA (miRNA) targets and the various downstream mechanisms of gene silencing, here we are interested in the regulation of a particular miRNA, let-7. The pluripotency factor Lin28 inhibits the biogenesis of the let-7 family of mammalian microRNAs. Lin28 is highly expressed in embryonic stem cells and has a fundamental role in regulation of development, glucose metabolism and tissue regeneration. Alternatively, Lin28 overexpression is correlated with the onset of numerous cancers, while let-7, a tumor suppressor, silences several human oncogenes. The Lin28/let-7 pathway is like a bistable switch. Each molecule represses expression of the other, and once the cell changes its state, the result is differentiation, or if the switch is reversed, cancer. At t h e molecular l e e l , Lin28 binds to precursor let-7 (pre-let-7) hairpins, triggering the 3' oligouridylation activity of TUT4 and/or TUT7. The oligoU tail added to pre-let-7 serves as a decay signal, as it is rapidly degraded by the exonuclease Dis3L2. In somatic cells, in the absence of L i n 2 8 , TUT4/7 promotes let-7 biogenesis by catalyzing single uridine addition to a subset of pre-let-7 miRNAs. Here, we propose to study the molecular basis of Lin28 mediated recruitment of TUT4/7 to pre-let-7, the switch in TUT4/7 activity between a monouridylase in the absence of Lin28 and an oligouridylase in the presence of Lin28, and the subsequent degradation of pre-let-7 by Dis3L2. We will utilize a similar approach to initiate an understanding of the broader role of TUT4/7 in marking both miRNA and mRNA with untemplated uridines.