SIGNAL TRANSDUCTION AND THE CONTROL OF DEVELOPMENT GENE EXPRESSION

一个非常简单的模型系统，细胞黏菌 Dictyosteoblasticdiscoideum，正被用于研究机制 在正常发育过程中， 分化 聚集后网骨藻细胞转录 另外26%的基因组不表达于 早期的预聚集阶段细胞。 细胞间的相互作用是一种 这些合成和稳定性的必要先决条件 新的分化特异性信使RNA。 另夕h 这些信使RNA的转录速率和稳定性是 进一步由环AMP介导的过程调节。 我们有 证明了1）溶解性营养剂，例如（NH 4）2SO 4 可以取代细胞间相互作用的需要， 基因表达; 2）cAMP作用于调节后聚集基因 通过细胞表面cAMP受体表达; 3） 分化特异性基因mRNA的积累 在前茎细胞中表达的蛋白通过不同的动力学机制进行调节， 细胞表面受体的形式比那些表达在 前孢子细胞; 4）cAMP受体相关的活化 腺苷酸环化酶在第二信使中不起作用 用于激活表达信号转导系统 5）前孢子基因 而不是前茎基因利用Ca++/钙调素依赖性的 第二信使信号转导系统 激活;最后，6）诱导表达的途径 前孢子细胞中的分化特异性基因抑制 在生长过程中转录的基因的表达。

A very simple model system, the cellular slime mold Dictyostelium discoideum, is being used to study mechanisms which control developmental gene activation during normal differentiation. Postaggregation Dictyostelium cells transcribe an additional 26% of their genome which is not expressed in earlier pre-aggregation stage cells. Cell-cell interaction is a necessary prerequisite for the synthesis and stability of these new differentiation-specific messenger RNAs. Additionally, the transcription rate and stability of these messenger RNAs are further regulated by a cyclic AMP-mediated process. We have demonstrated that 1) lyzosomatrophic agents such as (NH4)2S04 can replace the need for cell-cell interaction for postaggregation gene expression; 2) cAMP acts to regulate post aggregation gene expression through the cell surface cAMP receptor; 3) accumulation of mRNA for differentiation-specific genes expressed in prestalk cells is regulated though a different kinetic form of the cell surface receptor than those expressed in prespore cells; 4) activation of the cAMP receptor-associated adenylate cyclase does not play a role in the second messenger signal transduction system utilized for activation of expression of either the prespore or the prestalk genes; 5) prespore genes but not prestalk genes utilize a Ca++/Calmodulin-dependent second messenger signal transduction system for their activation; finally, 6) pathways that induce the expression of differentiation-specific genes in prespore cells suppress the expression of genes transcribed during growth.