Quiescent-induced transcriptional regulation

为了生存，有机体必须抵抗压力。静止(或G0)是细胞抵抗压力的一种适应性反应，输入a 可逆休眠，并能长时间存活。细胞如何进入、存活和退出G0是一个关键问题 在基础生物学方面，目前人们对此知之甚少。这是因为几十年来，G0经常被认为是一个 然而，最近的发现挑战了这一教条，并强调了 G0调节在包括癌症在内的几种人类病理中的重要性。治疗干预需要一个基本的 了解细胞如何转换到G0和G0，以及控制这些过程的分子开关。 值得注意的是，这些问题在很大程度上仍然是生物学中的悬而未决的问题。加入G0需要建立唯一的 转录状态，赋予G0细胞不同的特性。它还伴随着对 异染色质标记，表明异染色质蛋白有助于G0的建立。 为了解决这一知识差距，我们最近在分裂酵母细胞中模拟了G0。S.pombe中的G0有许多 与哺乳动物细胞的相似之处包括诱导信号(营养耗竭)、长寿命、对遗传毒性的抵抗力 药物，新陈代谢较低，并使用相同的生物途径(如自噬)和蛋白质复合体(如 蛋白酶体)。使用分裂酵母作为G0模型的主要优势是在氮饥饿(或葡萄糖)的情况下 剥夺)所有细胞均进入静止期，形成纯净的、同步的和等基因的G0细胞群体。我们 利用这些特性，并开发了一种时程G0分析来跟踪细胞活力、染色质、转录和小分子 RNA(SRNA)随时间变化。我们发现，随着细胞进入G0，一类新的与ArgAerte1(AGO1)相关的小分子 RNAs(G0 SRNAs)出现，它将构成异染色质的蛋白质部署到基因组的常染色质部分。 我们证明了RNAi和异染色质蛋白对于生存和G0计划的建立是必不可少的。 总体而言，我们发现了构成异染色质蛋白的一个新作用(G0中转录的全球调控) 和核Ago1相关的sRNA对长期应激的适应。在此基础上，我们提出了一个通用的模型。 真核生物中静止诱导的转录沉默(Quiets)，其中序列特异性的早期积累 在持续的压力下，因子(例如G0 sRNAs)针对调节蛋白的全球部署。在这项提案中，我们 将确定G0 SRNA是如何形成的(目标1)，并确定复合体和调节机制 平静(目标2)。我们还将测试这一机制的普遍性，以此作为对长期压力和 勾勒出宁静的核心目标和具体压力目标(目标3)。总括而言，拟议的研究将对我们的 对建立G0转录程序并可能重塑当前 真核生物中应激诱导转录调控的模型。我们预测，这些研究也可能揭露小说 G0病理的治疗靶点。

To survive, organisms must resist stress. Quiescence (or G0) is an adaptive response in which cells resist stress, enter a reversible dormancy and remain viable for long periods of time. How cells enter, survive and exit G0 is a critical question in basic biology, which is currently poorly understood. This is because for decades G0 was often deemed as an `uneventful' state in the cell cycle; however, recent discoveries have challenged this dogma and underscored the importance of G0 regulation in several human pathologies, including cancers. Therapeutic intervention requires a basic understanding of how cells transition to and from G0 and the molecular switches that govern these processes. Remarkably, these remain largely open questions in biology. G0 entry requires the establishment of a unique transcriptional state, which imparts distinct properties to G0 cells. It is also concomitant with redistribution of heterochromatic marks, suggesting that heterochromatin proteins contribute to G0 establishment. To address this knowledge gap, we recently modeled G0 in the fission yeast cells. G0 in S. pombe bears many similarities to that in mammalian cells including inducing signals (nutrient depletion), long life, resistance to genotoxic agents, lower metabolism, and use the same biological pathways (e.g. autophagy) and protein complexes (e.g. proteasome). The major advantage of using fission yeast as a G0 model is that upon nitrogen starvation (or glucose deprivation) all cells enter quiescence uniformly, creating pure, synchronous and isogenic populations of G0 cells. We exploited these features and developed a time-course G0 assays to track cell viability, chromatin, transcriptional and small RNA (sRNA) changes temporally. We found that as cells enter G0 a new class of Argonaute 1(Ago1)-associated small RNAs (G0 sRNAs) emerges, which deploys constitutive heterochromatin proteins to euchromatic parts of the genome. We showed that RNAi- and heterochromatin proteins are essential for survival and establishment of the G0 program. Overall, we discovered a novel role for constitutive heterochromatin proteins (global regulation of transcription in G0) and nuclear Ago1-associated sRNAs in adaptation to long-term stress. Based on these, we proposed a general model for Quiescent-induced Transcriptional Silencing (QuieTS) in eukaryotes, in which early accumulation of sequence specificity factors (e.g. G0 sRNAs) target the global deployment of regulatory proteins, under persistent stress. In this proposal, we will determine how G0 sRNA are formed (Aim 1), and identify the complexes and the mechanisms which mediate QuieTS (Aim 2). We will also test the generality of this mechanism as an adaptive response to long term stress and delineate the core and stress-specific targets of QuieTS (Aim 3). Overall, the proposed studies will greatly impact our understanding of the mechanisms by which G0 transcriptional programs are established and may reshape the current models of stress-induced transcriptional regulation in eukaryotes. We predict that these studies also may expose novel therapeutic targets for G0 pathologies.