Institut de Biologie Physico-chimique, Unité Propre de Recherche 9073, Centre National de la Recherche Scientifique affiliated with Université Paris Diderot, 75005 Paris, France.
Proc Natl Acad Sci U S A. 2012 May 1;109(18):7073-8. doi: 10.1073/pnas.1119802109. Epub 2012 Apr 12.
The bacteriophage T4-encoded RegB endoribonuclease is produced during the early stage of phage development and targets mostly (but not exclusively) the Shine-Dalgarno sequences of early genes. In this work, we show that the degradation of RegB-cleaved mRNAs depends on a functional T4 polynucleotide kinase/phosphatase (PNK). The 5'-OH produced by RegB cleavage is phosphorylated by the kinase activity of PNK. This modification allows host RNases G and E, with activity that is strongly stimulated by 5'-monophosphate termini, to attack mRNAs from the 5'-end, causing their destabilization. The PNK-dependent pathway of degradation becomes effective 5 min postinfection, consistent with our finding that several minutes are required for PNK to accumulate after infection. Our work emphasizes the importance of the nature of the 5' terminus for mRNA stability and depicts a pathway of mRNA degradation with 5'- to 3'-polarity in cells devoid of 5'-3' exonucleases. It also ascribes a role for T4 PNK during normal phage development.
噬菌体 T4 编码的 RegB 内切核糖核酸酶在噬菌体发育的早期阶段产生，主要（但并非专门）针对早期基因的 Shine-Dalgarno 序列。在这项工作中，我们表明，RegB 切割的 mRNA 的降解依赖于功能性 T4 多核苷酸激酶/磷酸酶（PNK）。RegB 切割产生的 5'-OH 由 PNK 的激酶活性磷酸化。这种修饰允许宿主核糖核酸酶 G 和 E 攻击从 5'端开始的 mRNA，导致它们的不稳定性，这两种酶的活性强烈受到 5'-单磷酸末端的刺激。降解的 PNK 依赖性途径在感染后 5 分钟变得有效，这与我们发现感染后需要几分钟才能积累 PNK 一致。我们的工作强调了 5'末端的性质对 mRNA 稳定性的重要性，并描绘了一种在缺乏 5'-3'外切核酸酶的细胞中具有 5'-3'极性的 mRNA 降解途径。它还赋予了 T4 PNK 在正常噬菌体发育过程中的作用。
