Regulation of Transcription Elongation in Adipose Homeostasis

对于参与组织生成和体内平衡的基因，RNA聚合酶II （Pol II）倾向于在其转录起始位点的下游立即暂停。与Pol II的从头招募相比，预组装和平衡的Pol II更有利于响应各种生理信号的快速和同步转录激活。然而，在组织生成和体内平衡的转录调节中，这种高度保守和普遍的现象的生物学意义几乎一无所知。我们最近观察到许多已知的脂肪生成基因表现出Pol II暂停。我们还发现，脂肪组织特异性消融关键的Pol ii暂停因子NELF会导致白色脂肪生成受损，但会升高与米色脂肪产热有关的基因的表达。在目前的提案中，我们将验证nelf介导的Pol II暂停在白色脂肪组织（WAT）稳态中起双重作用的中心假设：它促进脂肪祖细胞向成熟白色脂肪细胞的分化，并抑制白色到米色的相互转化。我们由实验室和临床科学家组成的多学科团队将使用小鼠遗传学、细胞培养系统和临床样本来验证这一创新假设。我们将首先使用小鼠和临床样本来确定NELF在WAT建立和维持中的细胞功能。然后，我们将使用新的小鼠遗传模型来评估NELF在米色脂肪产热中的作用。最后，我们将结合靶基因方法和基因组/生物信息学工具来询问nelf依赖的Pol II暂停和脂肪稳态中的转录调控。在我们提出的工作中，我们试图验证的新概念明显偏离了脂肪基因调控中普遍存在的以转录起始为中心的范式。特别是，新的Pol II暂停依赖机制为阐明调节脂肪稳态的转录网络指明了一个以前未被重视的方向。我们的研究在广泛的初步数据的支持下，一旦成功实施，有望对肥胖相关的代谢疾病产生新的见解。

For genes involved in tissue generation and homeostasis, RNA polymerase II (Pol II) tends to pause immediately downstream of their transcription start sites. Compared to de novo recruitment of Pol II, a preassembled and poised Pol II could be more conducive to rapid and synchronous transcriptional activation in response to various physiologic cues. However, virtually nothing is known about the biological significance of this highly conserved and prevalent phenomenon in transcriptional regulation of tissue generation and homeostasis. We recently observed that many known adipogenic genes exhibit Pol II pausing. We also found that adipose tissue-specific ablation of a key Pol II-pausing factor, NELF, results in impaired white adipogenesis but elevated expression of genes involved in beige adipose thermogenesis. In the current proposal, we will test the central hypothesis that NELF-mediated Pol II pausing plays a dual function in white adipose tissue (WAT) homeostasis: it promotes differentiation of adipose progenitor cells to mature white adipocytes, and suppresses white-to-beige inter-conversion. Our multidisciplinary team of laboratory and clinician scientists will use mouse genetics, cell culture systems, and clinical samples to test this innovative hypothesis. We will first use murine and clinical samples to determine the cellular function of NELF in WAT establishment and maintenance. We will then use new mouse genetic models to evaluate the role of NELF in beige adipose thermogenesis. Lastly, we will combine target-gene approaches and genomic/bioinformatics tools to interrogate NELF-dependent Pol II pausing and transcriptional regulation in adipose homeostasis. The novel concept we seek to validate in our proposed work clearly departs from the prevailing transcription initiation-centric paradigm in adipose gene regulation. In particular, the new Pol II pausing-dependent mechanism points to a previously unappreciated direction for elucidating the transcriptional network that regulates adipose homeostasis. When successfully executed, our studies, underpinned by extensive preliminary data, promise to yield new insights into obesity-related metabolic diseases.