Mar Janet, Walsh Charles J
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Exp Cell Res. 2008 Feb 15;314(4):896-902. doi: 10.1016/j.yexcr.2007.12.004. Epub 2007 Dec 14.
Four mRNAs (alpha- and beta-tubulin, flagellar calmodulin and Class-I), specifically expressed when Naegleria amebae differentiate into flagellates, were followed at 5-10 min intervals during the temperature-shock induction of multiple flagella in order to better understand how basal body and flagellum number are regulated. Surprisingly, tubulin synthesis continued during the 37 min temperature shock. An initial rapid decline in alpha- and beta-tubulin and flagellar calmodulin mRNAs was followed by a rapid re-accumulation of mRNAs before the temperature was lowered. mRNA levels continued to increase until they exceeded control levels by 4-21%. Temperature shock delayed flagella formation 37 min, produced twice as much tubulin protein synthesis and three fold more flagella. Labeling with an antibody against Naegleria centrin suggested that basal body formation was also delayed 30-40 min. An extended temperature shock demonstrated that lowering the temperature was not required for return of mRNAs to near control levels suggesting that induction of multiple flagella and the formation of flagella per se are affected in different ways. We suggest that temperature-shock induction of multiple flagella reflects increased mRNA accumulation combined with interference with the regulation of the recently reported microtubule-nucleating complex needed for basal body formation.
为了更好地理解基体和鞭毛数量是如何调控的，在嗜吞噬细胞阿米巴变形虫分化为鞭毛虫时特异性表达的四种mRNA（α-和β-微管蛋白、鞭毛钙调蛋白和I类），在多重鞭毛温度休克诱导过程中以5 - 10分钟的间隔进行跟踪。令人惊讶的是，在37分钟的温度休克期间微管蛋白合成仍在继续。α-和β-微管蛋白以及鞭毛钙调蛋白mRNA最初迅速下降，随后在温度降低之前mRNA迅速重新积累。mRNA水平持续增加，直到超过对照水平4 - 21%。温度休克使鞭毛形成延迟37分钟，产生的微管蛋白合成量是原来的两倍，鞭毛数量增加了两倍。用抗嗜吞噬细胞中心蛋白的抗体标记表明基体形成也延迟了30 - 40分钟。延长的温度休克表明，mRNA恢复到接近对照水平并不需要降低温度，这表明多重鞭毛的诱导和鞭毛本身的形成受到不同方式的影响。我们认为，多重鞭毛的温度休克诱导反映了mRNA积累增加，同时干扰了最近报道的基体形成所需的微管成核复合体的调控。
