Reduced action of polypeptide release factors induces mRNA cleavage and tmRNA tagging at stop codons in Escherichia coli
Reduced action of polypeptide release factors induces mRNA cleavage and tmRNA tagging at stop codons in Escherichia coli
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DOI：
10.1111/j.1365-2958.2006.05498.x
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发表时间：
2007-01-01
影响因子：
3.6
通讯作者：
Aiba, Hiroji
中科院分区：
文献类型：
--
作者：
Li, Xia;Yokota, Teruaki;Aiba, Hiroji
在大肠杆菌中，新生肽的某些C端序列可通过终止密码子处的tmRNA系统有效地标记蛋白质。在这里，我们表明，mRNA切割和tmRNA标签发生在UAG终止密码子识别的多肽释放因子1（RF-1）时，RF-1的活性被减少的prfA基因的突变，而不需要特定的新生肽的C-末端序列。当从质粒中提供野生型RF-1而不是RF-2时，消除了prfA突变体中的tmRNA标记和mRNA切割。此外，RF-1或RF-2的耗尽分别诱导核酸内切切割和UAG或UGA终止密码子处的tmRNA标记。我们的结论是，核糖体停滞在同源终止密码子所造成的减少活动或RF-1或RF-2的表达是负责mRNA切割。本数据沿着我们先前的研究强烈地表明，核糖体停滞导致mRNA的核酸内切切割，通常导致非终止mRNA，并且非终止mRNA的3'末端可能是tmRNA系统的唯一靶标。
Certain C-terminal sequences of nascent peptide cause an efficient protein tagging by tmRNA system at stop codons in Escherichia coli. Here, we demonstrate that both mRNA cleavage and tmRNA tagging occur at UAG stop codon recognized specifically by polypeptide release factor 1 (RF-1) when the activity of RF-1 is reduced by a mutation in the prfA gene without requirement of particular C-terminal sequences of nascent peptide. The tmRNA tagging and mRNA cleavage in the prfA mutant were eliminated when the wild-type RF-1 but not RF-2 was supplied from plasmid. In addition, depletion of either RF-1 or RF-2 induces endonucleolytic cleavage and tmRNA tagging at UAG or UGA stop codons respectively. We conclude that ribosome stalling at the cognate stop codon caused by reduced activity or expression of RF-1 or RF-2 is responsible for mRNA cleavage. The present data along with our previous studies strongly suggest that ribosome stalling leads to endonucleolytic cleavage of mRNA in general resulting in non-stop mRNA and that the 3' end of non-stop mRNA is probably only target for the tmRNA system.