Benedict M A, Desilver D A, Pelletier D E, Pentz W H, Ratner D I
Department of Biology, Amherst College, MA 01002.
Dev Genet. 1991;12(1-2):113-22. doi: 10.1002/dvg.1020120119.
It has been established previously that the maintenance of expression of prespore-specific genes of Dictyostelium discoideum is prevented by the translational inhibitor cycloheximide. The drug had no effect upon the level of transcripts of the other genes examined, prestalk-specific or cell type-nonspecific. However, the interpretation of this result is open to question, because of possible nonspecific effects of cycloheximide. We have now characterized the cellular specificity and temporal profiles of mRNA accumulation of additional Dictyostelium cDNA clones, and have examined other inhibitors of in vivo protein synthesis. Four structurally and mechanistically distinct translational inhibitors each prevented the reaccumulation of prespore transcripts in cyclic AMP-primed, disaggregated amoebae. These results establish the importance of developmental protein synthesis in the accumulation of prespore gene transcripts. Nuclear run-on transcription assays were used to learn whether protein synthesis is required primarily for mRNA synthesis or transcript stability. A transcriptional time course first demonstrated that the abundance of these cell-specific transcripts during development mirrors their rates of synthesis. Significantly, the protein synthesis requirement of the prespore genes examined also occurs at the level of mRNA transcription, implying the existence of one or more developmentally regulated transcriptional activators.
先前已经证实，翻译抑制剂环己酰亚胺可阻止盘基网柄菌芽孢前特异性基因的表达维持。该药物对所检测的其他基因（前柄特异性基因或细胞类型非特异性基因）的转录本水平没有影响。然而，由于环己酰亚胺可能存在非特异性效应，这一结果的解释存在疑问。我们现在已经对另外一些盘基网柄菌cDNA克隆的mRNA积累的细胞特异性和时间分布进行了表征，并研究了体内蛋白质合成的其他抑制剂。四种结构和作用机制不同的翻译抑制剂均能阻止环磷酸腺苷引发的、分散的变形虫中芽孢前转录本的重新积累。这些结果证实了发育性蛋白质合成在芽孢前基因转录本积累中的重要性。利用核转录分析来了解蛋白质合成主要是mRNA合成所必需的，还是转录本稳定性所必需的。转录时间进程首先表明，发育过程中这些细胞特异性转录本的丰度反映了它们的合成速率。值得注意的是，所检测的芽孢前基因对蛋白质合成的需求也发生在mRNA转录水平，这意味着存在一种或多种发育调控的转录激活因子。
