Role, function and regulation of human Dicer

调节哺乳动物基因组表达的分子机制比以前认为的更复杂，最近发现了基于小的非编码RNA种类（例如microRNA）的基因调节过程。microRNA在几乎所有活的真核生物中都有表达，它们共同调节人类约60%的基因，这表明我们体内的每一个生化和细胞过程都可能受到microRNA的控制！在人类中，microRNA是由核糖核酸酶III Dicer产生的，这是一种我们最初以重组形式发现和表征的大型酶。Dicer战略性地定位于核/细胞质界面，将从转运蛋白Exportin-5接受其核来源的microRNA前体（pre-microRNA）底物，通过其中央PIWI/Argonaute/Zwille（PAZ）结构域识别它，并通过其RNase IIIa和IIIb基序的协同作用释放microRNA。尽管它在microRNA生物发生中具有核心重要性，但Dicer在RNA沉默中发挥作用的细胞背景仍然知之甚少。在这个提议中，我们希望通过阐明人Dicer的蛋白质相互作用网络和表征人Dicer和细胞蛋白候选物之间的相互作用来解决这个问题，所述细胞蛋白候选物非常可能调节Dicer的各个方面，例如其细胞内定位、稳定性、持续合成能力、运输和与其他蛋白质相互作用的能力。我们的研究结果有望阐明调节人类基因组的机制，从而更好地理解microRNA生成酶Dicer的细胞作用、功能和调节。这是最终鉴定可能与Dicer功能改变有关或由microRNA通路故障引起的遗传疾病的先决条件。

The molecular mechanisms regulating the expression of mammalian genomes is more complex than previously thought, with the recent discovery of gene regulatory processes based on small non-coding RNA species, such as microRNAs. Expressed in almost all living eukaryotes, microRNAs act in concert to regulate ~60% of the genes in humans, suggesting that every biochemical and cellular processes may be under microRNA control in our body! In humans, microRNAs are generated by the ribonuclease III Dicer, a large enzyme that we discovered and characterized initially in its recombinant form. Strategically positioned at the nuclear/cytoplasmic interface, Dicer would accept its microRNA precursor (pre-microRNA) substrate of nuclear origin from the transporter Exportin-5, recognize it via its central PIWI/Argonaute/Zwille (PAZ) domain and release microRNAs through the concerted action of its RNase IIIa and IIIb motifs. Despite its central importance in microRNA biogenesis, the cellular context in which Dicer functions in RNA silencing still remains poorly understood. In this proposal, we wish to address that issue by elucidating the protein interaction network of human Dicer and characterizing the interaction between human Dicer and cellular protein candidates that are very likely to modulate various aspects of Dicer, such as its intracellular localization, stability, processivity, trafficking and ability to interact with other proteins. Expected to clarify the mechanisms regulating the human genome, our findings may provide a better understanding of the cellular role, function and regulation of the microRNA-generating enzyme Dicer. This is a prerequisite for eventually identifying genetic diseases possibly linked to alterations in Dicer function or caused by malfunctioning of the microRNA pathway.