Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33101, USA.
J Biol Chem. 2013 May 3;288(18):12574-9. doi: 10.1074/jbc.C113.459172. Epub 2013 Mar 26.
Processing of ribosomal RNA (rRNA) precursors is an important component of RNA metabolism in all cells. However, in no system have we yet identified all the RNases involved in this process. Here, we show that four 3'→5'-exoribonucleases, RNases II, R, and PH, and polynucleotide phosphorylase (PNPase), participate in maturation of the 3' end of 16S rRNA. In their absence, 16S precursor molecules with 33 extra 3'-nt accumulate; however, the presence of any one of the four RNases is sufficient to allow processing to occur, although with different efficiencies. Additionally, we find that in the absence of 3' maturation, 5' processing proceeds much less efficiently. Moreover, mutant 30S particles, containing immature 16S rRNA, form 70S ribosomes very poorly. These findings, together with the earlier discovery that RNases E and G are the 5'-processing enzymes, completes the catalogue of RNases involved in maturation of Escherichia coli 16S rRNA.
核糖体 RNA (rRNA) 前体的加工是所有细胞中 RNA 代谢的重要组成部分。然而，我们尚未在任何系统中鉴定出参与这一过程的所有核糖核酸酶。在这里，我们表明，四种 3'→5'-外切核糖核酸酶，RNase II、R 和 PH，以及多核苷酸磷酸化酶（PNPase），参与了 16S rRNA 3' 端的成熟。在它们缺失的情况下，会积累具有 33 个额外 3'-nt 的 16S 前体分子；然而，只要存在这四种核糖核酸酶中的任何一种，就足以允许进行加工，尽管效率不同。此外，我们发现，如果没有 3' 成熟，5' 加工的效率就会大大降低。此外，含有不成熟 16S rRNA 的突变 30S 颗粒形成 70S 核糖体的能力非常差。这些发现，加上早期发现 RNase E 和 G 是 5'-加工酶，完成了参与大肠杆菌 16S rRNA 成熟的核糖核酸酶目录。
