The let-7 Regulatory Network

 描述（由申请人提供） RNA干扰（RNAi）在植物和动物的发育、基因表达的转录后调节中发挥着重要作用，并且可以影响基因组组织和染色质结构。虽然许多研究都集中在microRNA（miRNA）靶点的识别和基因沉默的各种下游机制上，但在这里，我们感兴趣的是特定miRNA let-7的调控。多能性因子Lin 28抑制哺乳动物microRNA的let-7家族的生物发生。Lin 28在胚胎干细胞中高度表达，并在发育、葡萄糖代谢和组织再生的调节中发挥重要作用。或者，Lin 28过表达与许多癌症的发生相关，而let-7，一种肿瘤抑制因子，使几种人类癌基因沉默。Lin 28/let-7通路就像一个开关。每一种分子都抑制另一种分子的表达，一旦细胞改变了状态，结果就是分化，或者如果开关被逆转，就会发生癌症。在分子水平上，Lin 28与前体let-7（pre-let-7）发夹结合，触发了前体let-7的3'寡核苷酸化活性。 TUT 4和/或TUT 7。添加到pre-let-7的oligoU尾作为衰减信号，因为它被核酸外切酶Dis 3L 2快速降解。在体细胞中，在不存在Ln 28的情况下，TUT 4/7通过催化单个尿苷添加到pre-let-7 miRNA的子集来促进let-7生物合成。在这里，我们建议研究Lin 28介导的TUT 4/7向pre-let-7的募集的分子基础，在TUT 4/7活性中在Lin 28不存在下的单尿苷酶和Lin 28存在下的寡尿苷酶之间的切换，以及随后的Dis 3L 2对pre-let-7的降解。我们将利用类似的方法来开始理解TUT 4/7在用非模板尿苷标记miRNA和mRNA中的更广泛作用。

 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.