Lee J H, Walsh C J
Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260.
Mol Cell Biol. 1988 Jun;8(6):2280-7. doi: 10.1128/mcb.8.6.2280-2287.1988.
The nuclear run-on technique was used to measure the rate of transcription of flagellar genes during the differentiation of Naegleria gruberi amebae into flagellates. Synthesis of mRNAs for the axonemal proteins alpha- and beta-tubulin and flagellar calmodulin, as well as a coordinately regulated poly(A)+ RNA that codes for an unidentified protein, showed transient increases averaging 22-fold. The rate of synthesis of two poly(A)+ RNAs common to amebae and flagellates was low until the transcription of the flagellar genes began to decline, at which time synthesis of the RNAs found in amebae increased 3- to 10-fold. The observed changes in the rate of transcription can account quantitatively for the 20-fold increase in flagellar mRNA concentration during the differentiation. The data for the flagellar calmodulin gene demonstrate transcriptional regulation for a nontubulin axonemal protein. The data also demonstrate at least two programs of transcriptional regulation during the differentiation and raise the intriguing possibility that some significant fraction of the nearly 200 different proteins of the flagellar axoneme is transcriptionally regulated during the 1 h it takes N. gruberi amebae to form visible flagella.
运用核转录技术来测定纳氏虫变形虫分化为鞭毛虫过程中鞭毛基因的转录速率。编码轴丝蛋白α-微管蛋白、β-微管蛋白和鞭毛钙调蛋白的mRNA的合成，以及编码一种未鉴定蛋白质的协调调控的多聚腺苷酸（poly(A)）+RNA的合成，均呈现出平均22倍的瞬时增加。两种变形虫和鞭毛虫共有的多聚腺苷酸（poly(A)）+RNA的合成速率一直很低，直到鞭毛基因的转录开始下降，此时在变形虫中发现的RNA的合成增加了3至10倍。观察到的转录速率变化可以定量解释分化过程中鞭毛mRNA浓度增加20倍的现象。鞭毛钙调蛋白基因的数据证明了非微管轴丝蛋白的转录调控。这些数据还证明了分化过程中至少存在两个转录调控程序，并提出了一种有趣的可能性，即在纳氏虫变形虫形成可见鞭毛所需的1小时内，鞭毛轴丝中近200种不同蛋白质中的相当一部分受到转录调控。
