期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 378, 期 3, 页码 505-519出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2008.02.065
关键词
amino acid starvation; A-site mRNA cleavage; colicin D; ribosome pausing; tmRNA
资金
- NIGMS NIH HHS [GM078634, R01 GM078634, R01 GM078634-02] Funding Source: Medline
Escherichia coli possesses a unique RNase activity that cleaves stop codons in the ribosomal aminoacyl-tRNA binding site (A-site) during inefficient translation termination. This A-site mRNA cleavage allows recycling of arrested ribosomes by facilitating recruitment of the tmRNA circle SmpB ribosome rescue system. To test whether A-site nuclease activity also cleaves sense codons, we induced ribosome pausing at each of the six arginine codons using three strategies; rare codon usage, arginine starvation, and inactivation of arginine tRNAs with colicin D. In each instance, ribosome pausing induced mRNA cleavage within the target arginine codons, and resulted in tmRNA-mediated SsrA-peptide tagging of the nascent polypeptide. A-site mRNA cleavage did not require the stringent factor ppGpp, or bacterial toxins such as Re1E, which mediates a similar nuclease activity. However, the efficiency of A-site cleavage was modulated by the identity of the two codons immediately upstream (5' side) of the A-site codon. Starvation for histidine and tryptophan also induced A-site cleavage at histidine and tryptophan codons, respectively. Thus, A-site mRNA cleavage is a general response to ribosome pausing, capable of cleaving a variety of sense and stop codons. The induction of A-site. cleavage during amino acid starvation suggests this nuclease activity may help to regulate protein synthesis during nutritional stress. (C) 2008 Elsevier Ltd. All rights reserved.
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