The histone deacetylase SIRT6 modulates Transcriptional pausing

摘要 真核生物的基因组被包装在染色质中，这限制了RNA聚合酶的可及性 在转录过程中。最近在后生动物系统中的发现表明， 调节发生在聚合酶募集的下游，通过调节暂停和 早期伸长的效率（Adelman和Lis，2012）。尽管我们已经了解了一些分子 调节启动子近端暂停逃逸的参与者，无论是染色质可及性还是 哪些染色质修饰剂调节这一过程仍有待充分了解。值得注意的是， 最近发现组蛋白脱乙酰基酶SIRT 6是胚胎分化的中心调节因子， 代谢，调节关键发育和代谢基因的表达以适应营养物质 应力（Mostoslavsky等人，2006; Zhong等人，2010; Etchegaray等人，2015年）;此外，SIRT 6行为 作为肿瘤抑制剂，抑制癌代谢和Myc依赖性转录（塞巴斯蒂安等人， 2012; Kugel等人，2015; Kugel等人，2016）。这些研究表明，基因表达的微调 是维持细胞内稳态的关键。在本提案中，我们将测试以下创新想法： SIRT 6在聚合酶募集的下游起作用，调节启动子近端暂停， 新的，以前未确定的组蛋白去乙酰化酶的调节机制。具体而言，我们将1） 在分子水平上确定SIRT 6在转录延伸中的功能2）解密， 在生物化学上，SIRT 6是否使用确定的、完全重构的体外系统控制延伸， 生物化学测定以测试染色质化模板中的转录延伸。3)确定 SIRT 6在早期胚胎发育过程中转录延伸作用的生理相关性。 总的来说，我们的结果应该提供新的见解转录的分子机制， 调节，特别是与早期发育和对代谢线索的适应性反应有关的调节， 这些知识可能有助于治疗发育疾病、代谢疾病和癌症。

ABSTRACT The eukaryotic genome is packaged into chromatin, which limits the accessibility of RNA polymerase during transcription. Recent finding in metazoan systems have revealed that much of the transcription regulation occurs downstream of recruitment of the polymerase, through modulation of pausing and the efficiency of early elongation (Adelman and Lis, 2012). Although we have learned some of the molecular players that modulate escape from promoter proximal pausing, whether chromatin accessibility and which chromatin modifiers modulate this process, remains to be fully understood. Remarkably, we have recently identified the histone deacetylase SIRT6 as a central regulator of embryonic differentiation and metabolism, modulating expression of key developmental and metabolic genes to adapt against nutrient stress (Mostoslavsky et al., 2006; Zhong et al., 2010; Etchegaray et al., 2015); furthermore, SIRT6 acts as a tumor suppressor, inhibiting cancer metabolism amd Myc-dependent transcription (Sebastian et al., 2012; Kugel et al., 2015; Kugel et al., 2016). These studies indicate that fine-tuning of gene expression by SIRT6 is key to maintain cellular homeostasis. In this proposal, we will test the innovative idea that SIRT6 acts downstream of recruitment of the polymerase to modulate promoter proximal pausing, a novel, previously unidentified mechanism of regulation for an histone deacetylase. Specifically, we will 1) Determine, at the molecular level, the function of SIRT6 in transcriptional elongation 2) Decipher, biochemically, whether SIRT6 controls elongation using defined, fully reconstituted in-vitro systems and biochemical assays to test transcriptional elongation in chromatinized templates. 3) Determine the physiological relevance for SIRT6 roles in transcriptional elongation during early embryonic development. Overall, our results should provide new insights into the molecular mechanisms of transcriptional regulation, in particular those related to early development and adaptive responses to metabolic cues, a knowledge that may inform treatment against developmental diseases, metabolic diseases and cancer.