Molecular Noise, Transcription Errors and Heritable Phenotypic Change

描述（由申请人提供）：本研究的总体目标是确定在大肠杆菌细胞谱系中产生稳定表型的遗传调控网络（例如，转录开关）的永久化和扰动中，从DNA到蛋白质的信息传递错误的起源和后果。双稳态被认为是基因回路中的决策和记忆机制，依赖于低丰度转录因子之间的正反馈回路。该提议的中心假设是，从DNA到蛋白质的信息传递中的瞬时错误有助于蛋白质波动（分子噪声），并且当与非遗传调节网络相关联时，这些错误可以导致可遗传的非遗传表型异质性。具体来说，我们提出，由于转录、翻译或蛋白质折叠中的错误而导致的功能蛋白（在我们的情况下，是一种负调节其他基因表达的阻遏物）的短暂消失，可以在相同环境中生长的遗传相同的细胞中产生可遗传的表型变化。为了捕获和量化来自这种错误的瞬时事件，将使用两个良好表征的λ系统，乳糖操纵子和λ开关。在这些系统中，从一种表型状态到另一种表型状态的随机切换将是分子噪声的指示器。这项工作将阐明基于蛋白质的表观遗传开关的基本细胞/分子生物学，这可能对生物学和医学的许多基本方面至关重要，包括癌症，衰老，朊病毒发生和干细胞的多能性。

DESCRIPTION (provided by applicant): The overall goal of this research is to define the origins and the consequences of errors in information transfer from DNA to protein in the perpetuation and perturbation of genetic regulatory networks that generate stable phenotypes in cellular lineages of Escherichia coli, e.g. bistable switches. Bistability has been proposed as a mechanism for decision-making and memory in gene circuits, relying on positive feedback loops between transcription factors of low abundance. The central hypothesis of this proposal is that transient errors in the information transfer from DNA to protein contribute to protein fluctuation (molecular noise) and that these errors can cause heritable non-genetic phenotypic heterogeneity, when associated with bistable regulatory networks. Specifically, we propose that the transient disappearance of functional protein (in our case, a repressor that negatively regulates the expression of other genes) due to errors in transcription, translation, or protein folding can produce a heritable phenotypic change in genetically identical cells growing in the same environment. To capture and quantify transient events from such errors, two well characterized bistable systems will be used, the lactose operon and the lambda switch. In these systems, the stochastic switching from one phenotypic state to the alternative phenotypic state will be an indicator of molecular noise. This work will illuminate the fundamental cell/molecular biology of protein-based epigenetic switches, which are likely to be critical to many fundamental aspects of biology and medicine including cancer, aging, prion genesis, and pluripotency of stem cells.