Transcriptional-translational conflict in bladder epithelial homeostasis and cancer

摘要 染色质重塑和蛋白质合成是影响基因表达和蛋白质合成的严格调控过程。 细胞表型然而，目前尚不清楚这两种调节机制在多大程度上可能相互联系， 在控制正常上皮生理学和疾病状态方面独立。我们发现了一个新的函数 染色质重塑物ARID 1A与mRNA翻译延长之间的关系。这一环节涉及到 在膀胱癌发生的背景下维持细胞适应性，并代表了一种新的肿瘤抑制剂。 我们称之为转录-翻译冲突。ARID 1A的缺失会同时引发 致癌转录物，而且抑制翻译延伸因子eEF 2，这导致减少 蛋白质合成并预防癌症发病机制。但是，可以通过恢复 翻译延伸，这使得致癌mRNA的有效合成和癌症进展成为可能。这 这一发现提供了一个统一的基因表达模型，解释了为什么ARID 1A是一种环境特异性肿瘤 抑制器。重要的是，ARID 1A缺陷型肿瘤对翻译的药理学抑制保持敏感性 伸长起始最近，我们的实验室开发了新的体外和体内模型， 人类和小鼠ARID 1A缺陷型膀胱癌，我们也可以切换翻译延长。 我们已经使用这些模型来发现ARID 1A和mRNA翻译过程之间的关键联系 延长是至关重要的尿路上皮稳态和膀胱癌的进展。我们假设 缺乏ARID 1A的尿路上皮细胞中的转录-翻译冲突是通过减少真核细胞 延长因子2（eEF 2）的活性，当逆转时，释放出一个稳定的可药物致癌程序 足以推动癌症进展。我们的长期目标是利用最先进的小鼠模型， 原代类器官系统、全转录组多核糖体分析和患者来源的异种移植物， 研究ARID 1A与高度相关人群中蛋白质合成调控之间的基本联系 膀胱癌患者。为此，我们将解决以下目标：1）确定相关性， 尿路上皮细胞转化和癌变中的转录-翻译冲突机制;和2） 阐明基因表达平价如何使癌症进展，并代表特定背景的治疗 易损性.这项研究将帮助我们更深入地了解膀胱癌的生物学， 一种治疗致命疾病的新模式。我们的工作对以下方面的进展尤为重要： 精准医疗，因为它试图从机械上将一种高度流行的膀胱癌基因型（ARID 1A） 损失）的新的治疗模式，持有治疗膀胱癌患者的承诺。

ABSTRACT Chromatin remodeling and protein synthesis are tightly regulated processes that impact gene expression and cellular phenotypes. However, it is unknown to what extent these two regulatory mechanisms may be linked or independent in controlling normal epithelial physiology and disease states. We have uncovered a new functional relationship between the chromatin remodeler ARID1A and mRNA translation elongation. This link is involved in maintaining cellular fitness in the context of bladder carcinogenesis and represents a new tumor suppressive mechanism we call transcriptional-translational conflict. Loss of ARID1A triggers a simultaneous increase in oncogenic transcripts, but also inhibition of the translation elongation factor eEF2, which results in a reduction in protein synthesis and prevents cancer pathogenesis. However, this process can be reversed by restoring translation elongation, which enables the efficient synthesis of oncogenic mRNAs and cancer progression. This finding provides a unified gene expression model which explains why ARID1A is a context specific tumor suppressor. Importantly, ARID1A deficient tumors retain a sensitivity to pharmacologic inhibition of translation elongation initiation. Recently, our laboratory has developed and characterized new in vitro and in vivo models of both human and murine ARID1A deficient bladder cancer where we can also toggle translation elongation. We have used these models to discover a critical link between ARID1A and the process of mRNA translation elongation that is vital for urothelial homeostasis and bladder cancer progression. We hypothesize that transcriptional-translational conflict in urothelium lacking ARID1A is mediated through decreased eukaryotic elongation factor 2 (eEF2) activity, which when reversed unleashes a poised druggable oncogenic program sufficient to drive cancer progression. Our long-term objective is to utilize state-of-the-art mouse models and primary organoid systems, whole transcriptome polysome profiling, and patient derived xenografts to definitively investigate the fundamental link between ARID1A and protein synthesis regulation in a highly relevant population of bladder cancer patients. To do so, we will address the following aims: 1) Determine the relevance and mechanism of transcriptional-translational conflict in urothelial cell transformation and carcinogenesis; and 2) Elucidate how gene expression parity enables cancer progression and represents a context specific therapeutic vulnerability. This research will help us gain a deeper understanding of the biology of bladder cancer and open a new paradigm for treating patients with lethal disease. Our work is particularly important for the progress of precision medicine because it seeks to mechanistically tie a highly prevalent bladder cancer genotype (ARID1A loss) to a new treatment modality that holds therapeutic promise for bladder cancer patients.