Multi-layered Control of the Exit from Stemness

促进正常神经干细胞退出干细胞状态的机制可能也可以驱动大脑 肿瘤干细胞分化。因此，深入了解如何控制干性的退出将提高我们的 了解正常神经发生以及脑肿瘤的发展。从干性中退出，神经性的 干细胞后代必须在mRNA和蛋白质水平同步终止自我更新基因活性。 虽然对自我更新基因终止的理解已经取得了巨大的进展， 在从茎退出过程中的转录，很少有人知道如何转录后调控 机制终止自我更新基因活性。重要的是，没有人知道不同的控制 层协同作用以终止所有水平的自我更新基因活性。通过使用苍蝇II型神经 干细胞谱系作为范例，我们证明了转录，翻译和翻译后 作为同步终止自我更新的整合基因调控系统的一部分的控制功能 在干细胞后代中的所有水平的基因活性。在这篇文章中，我们将重点放在翻译和后... 自我更新基因活性的翻译控制。我们发现，RNA结合蛋白复合物， 在干细胞后代中活跃，通过结合独特的序列加速自我更新基因转录物的衰变 并同时募集多个去腺苷酶。此外，我们还发现， 通过多种泛素E3连接酶复合物快速和有效地引导蛋白质螯合和蛋白质水解， 强烈终止自我更新蛋白活性。从“开”到“关”状态的稳健转换也是可实现的。 需要精确的时空活动的许多发展信号机制，控制 图案化、增殖和细胞命运特化。深入了解我们提出的整合基因调控系统 将广泛适用于控制所有干细胞谱系中的干细胞性退出， 在正常发育过程中调节许多细胞命运决定。

The mechanisms promoting the exit from stemness in normal neural stem cells likely can also drive brain tumor stem cells to differentiate. Thus, insights into control of the exit from stemness will improve our understanding of normal neurogenesis as well as brain tumor development. To exit from stemness, neural stem cell progeny must synchronously terminate self-renewal gene activity at the level of mRNAs and proteins. While tremandous progress has been made toward understanding the termination of self-renewal gene transcription during the exit from stemness, little is known about how post-transcriptional regulatory mechanisms terminate self-renewal gene activity. Importantly, nothing is known about how distinct control layers function synergistically to terminate self-renewal gene activity at all levels. By using the fly type II neural stem cell lineage as a paradigm, we demonstrated that transcriptional, translational and post-translational control function as part of an integrated gene regulation system that synchronously terminates self-renewal gene activity at all levels in the stem cell progeny. In this proposal, we focus on translational and post- translational control of self-renewal gene activity. We showed that RNA-binding protein complexes that are active in the stem cell progeny expedite self-renewal gene transcripts for decay by binding unique sequences in their 3'UTRs and recruiting multiple deadenylase concurrently. In addition, we showed that the combined effect of protein sequestration and proteolysis directed by multiple ubiquitin E3 ligase complexes rapidly and robustly terminates self-renewal protein activity. A robust transition from an “ON” to an “OFF” state is also required for precise spatiotemporal activity of many developmental signaling mechanisms that control patterning, proliferation and cell fate specification. Insights into our proposed integrated gene regulation system will be broadly applicable to the control of the exit from stemness in all stem cell lineages as well as the regulation of numerous cell fate decisions during normal development.