Post-translational modification of RNase R is regulated by stress-dependent reduction in the acetylating enzyme Pka (YfiQ)
Post-translational modification of RNase R is regulated by stress-dependent reduction in the acetylating enzyme Pka (YfiQ)
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DOI：
10.1261/rna.030213.111
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发表时间：
2012-01-01
期刊：
影响因子：
4.5
通讯作者：
Deutscher, Murray P.
中科院分区：
文献类型：
--
作者：
Liang, Wenxing;Deutscher, Murray P.
RNase R是一种进行性核糖核酸外切酶，在大肠杆菌中结构RNA的降解中起重要作用。RNase R在指数期细胞中是不稳定的;然而，在某些应激条件下，RNase R水平由于其稳定性而显著增加。tmRNA和SmpB与RNase R的C-末端区域的结合是其不稳定性所必需的，并且这种结合在指数期细胞中通过单个残基Lys 544的乙酰化来调节。RNase R在固定相中不被乙酰化。我们在这里表明，只有指数期RNase R是乙酰化的，因为修饰酶，蛋白质赖氨酸乙酰转移酶，Pka（YfiQ），是不存在的指数后期和稳定期细胞。因此，新合成的RNase R保持不变。与预先存在的乙酰化RNase R的周转一起，没有修饰的RNase R保留在固定相中。我们发现，RNase R在冷休克细胞中也缺乏乙酰基修饰，由于缺乏PKA。这些数据表明RNase R的稳定性取决于Pka，Pka本身在胁迫条件下受到调节。
RNase R is a processive exoribonuclease that plays an important role in degradation of structured RNAs in Escherichia coli. RNase R is unstable in exponential phase cells; however, under certain stress conditions, RNase R levels increase dramatically due to its stabilization. Binding of tmRNA and SmpB to the C-terminal region of RNase R is required for its instability, and this binding is regulated by acetylation of a single residue, Lys544, in exponential phase cells. RNase R is not acetylated in stationary phase. We show here that only exponential phase RNase R is acetylated because the modifying enzyme, protein lysine acetyltransferase, Pka (YfiQ), is absent from late exponential and stationary phase cells. As a consequence, newly synthesized RNase R remains unmodified. Together with the turnover of preexisting acetylated RNase R, no modified RNase R remains in stationary phase. We find that RNase R in cold-shocked cells also lacks the acetyl modification due to the absence of Pka. These data indicate that RNase R stability depends on Pka, which itself is regulated under stress conditions.