Jenal U, Thurner C, Leisinger T
Mikrobiologisches Institut, Swiss Federal Institute of Technology, ETH-Zentrum, Zurich.
J Bacteriol. 1993 Sep;175(18):5945-52. doi: 10.1128/jb.175.18.5945-5952.1993.
In the thermophilic archaeon Methanobacterium thermoautotrophicum Marburg, the structural gene for isoleucyl-tRNA synthetase (ileS) is flanked upstream by orf401 and downstream by purL. orf401 encodes a 43.5-kDa protein with an unknown function. Northern (RNA) hybridization and S1 nuclease protection experiments showed that the orf401, ileS, and purL genes are cotranscribed from an archael consensus promoter in front of orf401. The corresponding transcript was about eightfold increased in cells that had been exposed to pseudomonic acid A, a specific inhibitor of isoleucyl-tRNA synthetase. Growth inhibition by puromycin, tryptophan starvation, or starvation for hydrogen did not affect the level of this transcript. The level of a trpE transcript, however, was drastically elevated upon tryptophan starvation, while inhibition by pseudomonic acid A had no effect on the level of this transcript. Expression of ileS thus appears to be controlled by a regulatory mechanism which specifically responds to the availability of isoleucyl-tRNA. Extensive decay of the orf401-ileS-purL message was observed. Degradation occurred, presumably by endonucleolytic cleavage, within the orf401 region.
在嗜热古菌嗜热自养甲烷杆菌马尔堡菌株中，异亮氨酰 - tRNA合成酶（ileS）的结构基因上游侧翼是orf401，下游侧翼是purL。orf401编码一种功能未知的43.5 kDa蛋白质。Northern（RNA）杂交和S1核酸酶保护实验表明，orf401、ileS和purL基因从orf401前面的古菌共有启动子共转录。在暴露于异亮氨酰 - tRNA合成酶的特异性抑制剂假单胞菌酸A的细胞中，相应的转录本增加了约八倍。嘌呤霉素抑制生长、色氨酸饥饿或氢气饥饿均不影响该转录本的水平。然而，色氨酸饥饿时trpE转录本的水平急剧升高，而异亮氨酰 - tRNA合成酶抑制剂假单胞菌酸A对该转录本的水平没有影响。因此，ileS的表达似乎受一种调节机制控制，该机制对异亮氨酰 - tRNA的可用性有特异性反应。观察到orf401 - ileS - purL信使RNA大量降解。降解可能是通过核酸内切酶切割在orf401区域内发生的。
