SIGNAL TRANSDUCTION AND THE CONTROL OF DEVELOPMENT GENE EXPRESSION

一个非常简单的模型系统，细胞黏液霉菌Dictyostelials Discoideum正被用来研究控制 发育基因在正常分化过程中的激活。 Dictyostelius细胞聚集后转录额外26% 它们的基因组在早期的预聚集中热表达 分期细胞。细胞与细胞之间的相互作用是 这些新分化特异体的合成及其稳定性 信使RNA。此外，转录速度和稳定性 在这些信使RNA中，进一步受环状AMP- 调解过程。我们已经证明：1)溶血萎缩性 像(NH4)2S04这样的试剂可以取代细胞-细胞的需要 聚集后基因表达的相互作用；2)cAMP作用于 通过细胞表面调节聚集后基因的表达 CAMP受体；3)分化特异的mRNA积聚 在前柄细胞中表达的基因是通过不同的 细胞表面受体的动力学形式比在 前孢子细胞；4)cAMP受体相关激活 腺苷环化酶在第二信使中不起作用 用于激活表达的信号转导系统 前孢子或前柄基因；5)前孢子基因 但不是前茎基因利用钙离子/钙调蛋白依赖的第二个 信使信号转导系统激活它们；6) 诱导分化特异性基因表达的途径 前孢子细胞中的基因抑制基因的表达 在生长过程中转录；最后，分析其中一个cAMP 调控的前孢子基因揭示了它与 神经黏附蛋白N-CAM及其合成和表达 细胞表面外观以严格的顺序交替 细胞表面黏附分子在形态发生的关键阶段。

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 hot 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 through 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; 6) pathways that induce the expression of differentiation-specific genes in prespore cells suppress the expression of genes transcribed during growth; finally, 7) analysis of one of the cAMP regulated prespore genes reveals that it is highly homologous to the neural adhesion protein N-CAM and that both its synthesis and cell surface appearance alternate in strict sequence with another cell surface adhesion molecule at key morphogenetic stages.