Regulatory Processes Involved in the Transition from Growth to Development in Dictyostelium

许多发育系统的一个基本原则是细胞生长和细胞分化的互斥性。Dictyostelium disideum为研究这种相互关系提供了一个模型，在植物状态下，变形虫通过生长和有丝分裂具有无限的自我更新能力，而发育程序的启动导致生长和分裂的停止并导致细胞分化。在过去的授权期间，从生长到发育转换的调节机制已经被调查，主要是检查各种基因的差异表达。我们建议通过研究导致其中一个基因V4转录失活的分子机制来继续这一方法，以响应生长停止和发育程序的激活。这将通过检查参与V4基因表达的蛋白质因子，以及这些因子的活性如何与从生长到发育的转变相关联来完成。V4基因的表达对环境中存在的营养物质的水平和类型高度敏感。此外，V4基因的编码产物已被证明是从生长到发育过渡所必需的，它参与了所有被检测的生长特异性基因的表达失活，并参与了大多数“早期发育特异性”基因的表达诱导。该基因产物在导致生长停止和启动发育程序中的作用以及它如何参与调节上述基因的表达将被研究。这将需要编码蛋白的生产和纯化，检查与之相关的任何活性，确定其细胞位置，修饰状态，并识别可能与之相互作用的其他蛋白质。将研究V4基因产物与其他几个被认为参与发育过程早期调控事件的因素之间可能的相互作用。

A fundamental principle of many developing systems is the mutually exclusive nature of cell growth and cellular differentiation. Dictyostelium discoideum provides a model for investigating this reciprocal relationship in that in the vegetative state the amoebae have an unlimited capacity for self renewal through growth and mitotic divisions while initiation of the developmental program results in a cessation of growth and division and leads to cellular differentiation. During the past granting period, the regulatory mechanisms underlying the switch from growth to development have been investigated primarily be examining the resulting differential expression of a variety of genes. It is proposed to continue this approach by investigating the molecular mechanisms bringing about the deactivation of transcription of one of these genes, V4, in response to cessation of growth and activation of the developmental program. This will be done by examining the protein factors involved in the expression of the V4 gene, and how the activity of these factors is coupled to the transition from growth to development. V4 gene expression is highly sensitive to levels and types of nutrients present in the environment. In addition, the encoded product of the V4 gene has been shown to be required for the transition from growth to development, and it is involved in the deactivation of expression of all growth specific genes examined and in the induction of expression of most "early developmental specific" genes. The role of this gene product in bringing about a cessation of growth and in initiating the developmental program and how it is involved in regulating the expression of the above mentioned genes will be examined. This will require production and purification of the encoded protein, examining any activity associated with it, and determining its cellular location, its modification state(s), and identifying other proteins which may interact with it. The possible interplay between the V4 gene product and several other factors postulated to be involved in the early regulatory events of the developmental program will be investigated.