Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33101, USA.
RNA. 2010 Apr;16(4):667-72. doi: 10.1261/rna.1981010. Epub 2010 Feb 25.
RNase R is an important exoribonuclease that participates in the degradation of structured RNAs in Escherichia coli. In earlier work, it was shown that RNase R levels increase dramatically under certain stress conditions, particularly during cold shock and stationary phase. However, the regulatory processes that lead to this elevation are not well understood. We show here that the increase in RNase R in stationary phase is unaffected by the global regulators, RpoS and (p)ppGpp, and that it occurs despite a major reduction in rnr message. Rather, we find that RNase R is a highly unstable protein in exponential phase, with a half-life of approximately 10 min, and that the protein is stabilized in stationary phase, leading to its relative increase. RNase R is also stabilized during cold shock and by growth in minimal medium, two other conditions that lead to its elevation. These data demonstrate that RNase R is subject to regulation by a novel, posttranslational mechanism that may have important implications for our complete understanding of RNA metabolism.
核糖核酸酶 R 是一种重要的外切核糖核酸酶，参与大肠杆菌中结构 RNA 的降解。在早期的研究中，已经表明核糖核酸酶 R 的水平在某些应激条件下会显著增加，特别是在冷休克和静止期。然而，导致这种升高的调控过程还不是很清楚。我们在这里表明，静止期核糖核酸酶 R 的增加不受全局调控因子 RpoS 和 (p)ppGpp 的影响，尽管 rnr 信使有很大的减少。相反，我们发现核糖核酸酶 R 在指数期是一种高度不稳定的蛋白质，半衰期约为 10 分钟，并且在静止期蛋白质被稳定，导致其相对增加。在冷休克和最小培养基中生长时，核糖核酸酶 R 也会稳定，这两种情况都会导致其水平升高。这些数据表明，核糖核酸酶 R 受到一种新的翻译后调控机制的调控，这可能对我们全面理解 RNA 代谢具有重要意义。
