TRANSDUCTION OF THE A SIGNAL IN MYXOCOCCUS DEVELOPMENT

黄色粘球菌是一个很好的模型系统 细胞-细胞信号通路如何控制的基本问题 多细胞发育。这些问题都与所有正常情况相关 胚胎和成体细胞传递信号以协调过程 例如生长和分化，以及 信号网络有缺陷，如癌细胞。 通过早期多细胞发育的进展需要M。 黄花细胞对高细胞密度和营养物质有感觉和反应 限制。两个敏感的传感网络监测这些 细胞外信号在M早期的关键检查点会聚。 黄花发展。此检查点可以通过 特异基因，4521；只有在条件适合于早期M。 黄花的发育就是这个基因的表达。这样做的长期目标是 研究将确定：i)细胞如何感知和转导 细胞密度信号？二)细胞密度和营养感知如何 路径整合？三)年的变化之间有什么联系 基因表达与多细胞复杂行为反应 子实体形成？ 为了回答这些问题，我们的研究重点是识别和 表征连接单元密度信号的电路， 细胞外A信号，对其反应基因。技术和技术 经典遗传学和分子遗传学与蛋白质生物化学相结合，将 被用来描述A信号转导途径。我们预计 通过这次调查，也通过以下方式深入了解这一机制 黄色微囊藻融合了细胞密度和营养信息。 具体地说，我们建议：i)表征其结构和功能 SASB基因座，4521表达的负调控基因，被认为是一个 A信号通路的组成部分；ii)鉴定和表征 通过突变分析控制4521基因表达的顺式作用元件； 三)通过下列方式确定4521表达的直接调控因素并确定其特征 4521上游结合蛋白的纯化和鉴定 监管区域。编码这些蛋白质的基因将被识别出来。 并经DNA序列分析和诱变鉴定；iv) 通过遗传分析确定A信号的其他成分 以及v)表征其他早期的A信号依赖 通过克隆、定位和测序来促进发育 地区。

Myxococcus xanthus represents an excellent model system to address fundamental questions of how cell-cell signaling pathways control multicellular development. These questions are relevant to all normal embryonic and adult cells which transduce signals to coordinate processes such as growth and differentiation, as well as to cells which are defective in signaling networks, such as cancer cells. Progression through early multicellular development requires that M. xanthus cells sense and respond to a high cell density and nutrient limitation. Two sensitive sensing networks which monitor these extracellular signals converge at a critical check point early in M. xanthus development. This check point can be monitored by expression of a specific gene, 4521; only if the conditions are correct for early M. xanthus development is this gene expressed. The long term goals of this research are to determine: i) How do the cells sense and transduce the cell-density signal? ii) How are the cell-density-and nutrient-sensing pathways integrated? iii) What is the connection between the change in gene expression and the complex behavioral response of multicellular fruiting body formation? To answer these questions our research focuses on identifying and characterizing the circuitry that connects the cell-density signal, extracellular A signal, to its responsive gene. The techniques of classical and molecular genetics, combined with protein biochemistry, will be used to characterize the A signal transduction pathway. We expect through this investigation to also gain insights into the mechanism by which M. xanthus integrates cell density and nutritional information. Specifically, we propose: i) to characterize the structure and function of sasB locus, a negative regulator of 4521 expression, thought to be a component of the A signaling pathway; ii) to identify and characterize the cis-acting elements controlling 4521 expression by mutational analysis; iii) to identify and characterize direct regulators of 4521 expression by purifying and characterizing proteins that bind to the 4521 upstream regulatory region. The genes encoding these proteins will be identified and characterized by DNA sequence analysis and mutagenesis; iv) to identify by genetic analysis additional components of the A signal pathway; and v) to characterize other early A signal-dependent developmental promoters by cloning, localizing, and sequencing these regions.