Consequences and Control of Randomness in Timing of Intracellular

项目概要/摘要： 在单个细胞的水平上，基因的表达在生物体中具有内在的随机性 从原核生物到人类细胞。随机表达表现为细胞对细胞 基因产物水平的变化，甚至在同基因细胞之间，这种变化显着 影响生物学功能和表型。细胞如何确保关键时间的精确性 面对随机表达的细胞内事件是一个有趣的基本问题。 研究事件发生时间的一个简单模型是噬菌体λ的裂解系统，其中噬菌体λ的裂解是由噬菌体λ的裂解引起的。 感染E.当一种蛋白质holin在大肠杆菌细胞中达到临界阈值浓度时， 细胞膜有趣的是，初步数据揭示了时间的精确性：单个细胞在 最佳安排的时间，具有最小的定时统计波动。的关键目标 这个建议是使用λ的裂解系统来揭示调控机制， 在单小区级别缓冲定时中的噪声。从数学上讲，事件定时中的噪声是 使用首次通过时间框架进行调查，其中当事件发生时触发事件， 随机过程（Holin水平）第一次达到阈值。新的分析计算 首次通过时间将用于基因表达和调控的随机模型 复杂程度各不相同将理论结果与单细胞裂解时间测量相结合 在野生型和突变体中，控制随机性的机制在时间上是随机的。 将表征细胞内事件。此外，我们将使用数学的组合 模型和实验，以确定裂解时间的随机性如何驱动细胞间 每个细胞的λ子代计数的变化。 这里开发的第一次通过时间框架是相当普遍的，因为不同细胞的时间选择是不同的。 过程取决于调节分子达到临界阈值水平。鉴定 缓冲细胞内事件发生时间的随机性的调节基序具有后果 用于细胞周期控制和开发，其中需要精确度以获得适当的系统 功能λ裂解系统的定量表征对于新兴的医学研究也至关重要。 例如使用holin蛋白质靶向癌细胞和致病细菌。

Project Summary/Abstract: At the level of individual cells, expression of genes is inherently stochastic across organisms ranging from prokaryotes to human cells. Stochastic expression manifests as cell-to-cell variation in gene product levels even among isogenic cells, and this variation significantly affects biological functions and phenotype. How cells ensure precision in the timing of key intracellular events in the face of of stochastic expression is an intriguing fundamental problem. One simple model for studying event timing is the phage λ's lysis system, where lysis of the infected E. coli cell occurs when a protein, holin, reaches a critical threshold concentration in the cell membrane. Intriguingly, preliminary data reveals precision in timing: individual cells lyse at an optimally scheduled time with minimal statistical fluctuations in timing. The key objective of this proposal is to use λ's lysis system to uncover regulatory mechanisms essential for buffering noise in timing at the single-cell level. Mathematically, noise in the event timing is investigated using the first-passage time framework, where an event is triggered when a stochastic process (holin level) hits a threshold for the first time. Novel analytical calculations of the first-passage time will be performed for stochastic models of gene expression and regulation of varying complexities. Combining theoretical results with single-cell lysis time measurements in both wild-type and mutant phages, the mechanisms controlling stochasticity in the timing of intracellular events will be characterized. In addition, we will use combination of mathematical models and experiments to determine how stochasticity in lysis times drives intercellular variations in the λ progeny count per cell. The first-passage time framework developed here is quite general as timing of diverse cellular processes depends on regulatory molecules reaching critical threshold levels. Identification of regulatory motifs that buffer randomness in the timing of intracellular events has consequences for cell-cycle control and development, where precision is required for proper system functioning. Quantitative characterization of λ's lysis system is also critical for emerging medical applications such as using holin proteins for targeting cancer cells and pathogenic bacteria.