Information Integration and Energy Expenditure in Eukaryotic Gene Regulation

项目摘要 基因调控--基因如何在正确的地点、正确的时间和正确的数量被激活--是一种 这是生物学和医学的大多数领域的核心问题。我们对基因调控的理解源于 细菌的经典研究：被称为“转录因子”(TF)的蛋白质结合到调节的DNA序列和 招募RNA聚合酶(RNAP)。真核生物的情况要复杂得多。例如，真核生物 DNA在核小体周围包装成染色质，并使用外部能源，如三磷酸腺苷 重组染色质，重塑核小体，并在翻译后修饰调节蛋白。开拓性 来自几个实验室的研究已经确定了参与这一调控的许多分子成分 复杂性。然而，用来推理真核基因调控的定量概念仍然是 很大程度上是基于细菌的范例。我们的工作重点是解决这一令人震惊的差距。此前，我们 通过将植根于物理的数学模型与 果蝇早期胚胎的定量和合成实验。果蝇提供了一个无与伦比的模型 测量和扰乱生物体内基因调控的系统。数学利用了一张图- 基于马尔可夫过程的方法，允许对所需的量进行代数计算。这使我们能够 确定能量消耗的功能限制，同时避免将模型与数据或数值相匹配 模拟微分方程式。我们已经提供了强有力的证据表明，能源消耗远离 热力学平衡对真核基因的功能性质至关重要。在现在 提议，我们建立在这一先前战略的基础上。我们假设来自果蝇驼背基因的数据 不能用任何RNAP调节补充的热力学平衡模型来解释，无论 分子细节是多么复杂。我们相信我们可以利用一种方法在 线性框架来建立这一非常强大的结果。然后我们将扩展我们的实验方法 以及超越规范招募的建模，以分析RNAP本身的动态和随机 信使核糖核酸的产生。我们将引入对转录因子的mRNA和光遗传扰动的实时成像来 测量基因表达的量化方面，并将扩展我们的代数方法以适应 这样的数据。我们假设基因调控中的能量消耗对于调节RNAP是必不可少的。 动态，并产生观察到的驼背mRNA表达的随机模式。我们的努力将 制定集调控、能源支出、RNAP动态和经济增长于一体的驼背新模式 MRNA的随机性。

Project Abstract Gene regulation – how genes are turned on in the right place, at the right time and in the right amount – is a problem central to most areas of biology and medicine. Our understanding of gene regulation arose from classical studies in bacteria: proteins called “transcription factors” (TFs) bind to regulatory DNA sequences and recruit RNA polymerase (RNAP). The situation in eukaryotes is far more complicated. For example, eukaryotic DNA is packaged around nucleosomes into chromatin and external sources of energy, such as ATP, are used to reorganise chromatin, remodel nucleosomes and post-translationally modify regulatory proteins. Pioneering studies from several laboratories have identified many of the molecular components involved in this regulatory complexity. However, the quantitative concepts used to reason about eukaryotic gene regulation are still largely based on the bacterial paradigm. Our work focuses on addressing this alarming gap. Previously, we developed a strategy of “following the energy” by integrating mathematical models rooted in physics with quantitative and synthetic experiments in the early Drosophila embryo. The fruit fly offers an unrivaled model system for measuring and perturbing gene regulation in a living organism. The mathematics exploits a graph- based approach to Markov processes that permits algebraic calculation of required quantities. This allowed us to identify the functional limits to energy expenditure, while avoiding fitting models to data or numerically simulating differential equations. We have provided strong evidence that energy expenditure away from thermodynamic equilibrium is essential for the functional properties of eukaryotic genes. In the present proposal, we build on this previous strategy. We hypothesize that data from the Drosophila hunchback gene cannot be accounted for by any thermodynamic equilibrium model of regulated recruitment of RNAP, no matter how complicated the molecular details. We believe we can exploit a method of “coarse graining” within the linear framework to establish this remarkably powerful result. We will then extend our experimental methods and modeling beyond regulated recruitment, to analyze the dynamics of RNAP itself and the stochastic production of mRNA. We will introduce real-time imaging of mRNA and optogenetic perturbations of TFs to measure quantitative aspects of gene expression, and will extend our algebraic methods to accommodate such data. We hypothesize that energy expenditure in gene regulation is essential to modulate RNAP dynamics and generate the observed stochastic patterns of hunchback mRNA expression. Our efforts will formulate a new model of hunchback that integrates regulation, energy expenditure, RNAP dynamics and mRNA stochasticity.