Cheng Zhuan-Fen, Deutscher Murray P
Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, FL 33101, USA.
Mol Cell. 2005 Jan 21;17(2):313-8. doi: 10.1016/j.molcel.2004.11.048.
mRNA decay is a major determinant of gene expression. In Escherichia coli, message degradation initiates with an endoribonucleolytic cleavage followed by exoribonuclease digestion to generate 5'-mononucleotides. Although the 3' to 5' processive exoribonucleases, PNPase and RNase II, have long been considered to be mediators of this digestion, we show here that another enzyme, RNase R, also participates in the process. RNase R is particularly important for removing mRNA fragments with extensive secondary structure, such as those derived from the many mRNAs that contain REP elements. In the absence of RNase R and PNPase, REP-containing fragments accumulate to high levels. RNase R is unusual among exoribonucleases in that, by itself, it can digest through extensive secondary structure provided that a single-stranded binding region, such as a poly(A) tail, is present. These data demonstrate that RNase R, which is widespread in prokaryotes and eukaryotes, is an important participant in mRNA decay.
mRNA 降解是基因表达的主要决定因素。在大肠杆菌中，信使 RNA 的降解始于核糖核酸内切酶的切割，随后由核糖核酸外切酶消化产生 5'-单核苷酸。尽管 3' 到 5' 方向的连续性核糖核酸外切酶 PNPase 和 RNase II 长期以来被认为是这种消化作用的介质，但我们在此表明，另一种酶 RNase R 也参与了这一过程。RNase R 对于去除具有广泛二级结构的 mRNA 片段尤为重要，例如那些来自许多含有 REP 元件的 mRNA 的片段。在缺乏 RNase R 和 PNPase 的情况下，含 REP 的片段会积累到很高的水平。RNase R 在核糖核酸外切酶中是不同寻常的，因为只要存在一个单链结合区域，如 poly(A) 尾，它自身就能消化通过广泛的二级结构。这些数据表明，在原核生物和真核生物中广泛存在的 RNase R 是 mRNA 降解的重要参与者。
