Combinatorial regulation of the enhancer codes in senescence

摘要 基于对细胞衰老的新认识的重要性，我们开始了研究， 是否存在一种特定的增强子激活“密码”， 鉴定负责的DNA结合转录因子。虽然有迅速崛起，现在 无可辩驳的证据表明，每种细胞类型中的40- 70，000个增强子在发育、稳态 并且，通常，病理事件，它们在细胞衰老中的作用仍然不明确。此外，虽然细胞 衰老代表了衰老的基本过程和病理学的已知驱动因素， 新激活的增强子群是衰老进展的基础，但仍知之甚少。因此，我们认为， 这项建议的目的是检验一个新的假设，即在大规模的初步数据的支持下， 两组特定增强子的新出现启动了一种渐进的，功能上- 重要的是，基因转录程序的改变。根据我们对改变的增强子的研究， 在复制衰老过程中的染色体景观，我们已经开始建立， mTOR抑制剂雷帕霉素显著延迟细胞衰老的所有方面，包括细胞衰老的出现。 新的功能性增强剂我们的重点是阐明获得增强子程序的功能重要性 细胞衰老的基础，并确定关键的DNA结合转录因子的基础， 转录程序是复制衰老的决定因素，基于互补的专业知识， 苏和罗森菲尔德实验室的人具体而言：i）我们将使用无偏见的屏幕来记录至少 两个不同的激活增强子网络独立调节增殖阻滞和SASP方面 复制性衰老。ii）我们将确定与 以前未识别的转录因子，NFI-A，NFI-C，调节获得的增强子， 增殖抑制，以及那些与SMAD 2/3和NF κ B一起调节SASP程序的细胞。同时，我们 可能会牵连到潜在的信号通路。iii）我们将识别以前未识别的组蛋白 的修饰特征，以及它们在复制衰老中的功能重要性。（四）我们将确定 激活素和TGF β 2分别作为增殖和SASP增强子程序的抑制剂。我们的建议 有望为启动和维持衰老细胞的分子事件提供变革性的见解 表型，并帮助阐明潜在的新的治疗方式对有害的SASP程序。

Abstract Based on the importance of defining new insights into cellular senescence, we initiated studies to investigate whether there might be a specific enhancer activation “code” that underlies cellular senescence for identifying the responsible DNA binding transcription factors. While there is rapidly-emerging, and now unassailable evidence, on the role of the 40-70,000 enhancers in each cell type in development, homeostasis and, often, pathological events, their role in cellular senescence remains undefined. Furthermore, while cellular senescence represents a fundamental process of aging and a known driver of pathologies, the causative role of newly activated enhancer cohorts underlying progression of senescence remain poorly understood. Therefore, the goal of this proposal, supported by extensive preliminary data, is to test a novel hypothesis that the de novo appearance of two specific cohorts of enhancers sets into motion a progressive, functionally- important, alteration in gene transcription programs. Based on our study of the altered enhancer and chromosomal landscape during replicative senescence, we have begun to establish that the geroprotective mTOR inhibitor, Rapamycin, markedly delays all aspects of cellular senescence, including the appearance of new, functional, enhancers. Our focus is to elucidate the functional importance of a gained enhancer program underlying cellular senescence, and identify the critical DNA binding transcription factors underlying the transcriptional programs that are determinants of replicative senescence, based on the complementary expertise of the Suh and Rosenfeld laboratories. Specifically: i) We will use unbiased screens to document that at least two distinct activated enhancer networks independently regulate the proliferation arrest and SASP aspects of replicative senescence, respectively. ii) We will identify combinatorial factors synergizing with the previously-unrecognized transcription factors, NFI-A, NFI-C, to regulate the gained enhancers underling proliferation arrest, and those that, with SMAD2/3 and NFkB, to regulate the SASP program. In parallel, we can implicate the underlying signaling pathways. iii) We will identify previously unrecognized histone modification signatures of, and their functional importance in replicative senescence . iv) We will Identify Activin and Tgf2 as inhibitors of the proliferation and SASP enhancer programs, respectively. Our proposal promises to provide transformative insights into molecular events that initiate and perpetuate the senescent cell phenotypes, and help elucidate potential novel therapeutic modalities against the deleterious SASP program.