Dreyfus Marc
Expression Genetique Microbienne, Paris, France.
Prog Mol Biol Transl Sci. 2009;85:423-66. doi: 10.1016/S0079-6603(08)00811-8.
In prokaryotes, translation influences mRNA decay. The breakdown of most Escherichia coli mRNAs is initiated by RNase E, a 5'-dependent endonuclease. Some mRNAs are protected by ribosomes even if these are located far upstream of cleavage sites ("protection at a distance"), whereas others require direct shielding of these sites. I argue that these situations reflect different modes of interaction of RNase E with mRNAs. Protection at a distance is most impressive in Bacilli, where ribosomes can protect kilobases of unstable downstream sequences. I propose that this protection reflects the role in mRNA decay of RNase J1, a 5'-->3' exonuclease with no E. coli equivalent. Finally, recent years have shown that besides their protective role, ribosomes can also cleave their mRNA under circumstances that cause ribosome stalling. The endonuclease associated with this "killing" activity, which has a eukaryotic counterpart ("no-go decay"), is not characterized; it may be borne by the distressed ribosome itself.
在原核生物中，翻译会影响信使核糖核酸（mRNA）的降解。大多数大肠杆菌信使核糖核酸的降解是由核糖核酸酶E（RNase E）启动的，它是一种依赖于5'端的内切核酸酶。一些信使核糖核酸即使核糖体位于切割位点的上游很远的地方也能受到保护（“远距离保护”），而其他信使核糖核酸则需要这些位点的直接屏蔽。我认为这些情况反映了核糖核酸酶E与信使核糖核酸相互作用的不同模式。远距离保护在芽孢杆菌中最为显著，在那里核糖体能保护不稳定的下游序列的千碱基。我提出这种保护反映了核糖核酸酶J1在信使核糖核酸降解中的作用，它是一种5'→3'外切核酸酶，在大肠杆菌中没有与之对应的酶。最后，近年来的研究表明，除了其保护作用外，核糖体在导致核糖体停滞的情况下也能切割其信使核糖核酸。与这种“杀伤”活性相关的内切核酸酶，在真核生物中有对应的酶（“无义介导的mRNA降解”），尚未得到表征；它可能由受困的核糖体本身携带。
