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Nucleic Acids Res. 2014 Jun;42(10):6448-62. doi: 10.1093/nar/gku279. Epub 2014 Apr 19.

RalR (a DNase) and RalA (a small RNA) form a type I toxin-antitoxin system in Escherichia coli.

Author information

1
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, PR China.
2
Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802-4400, USA.
3
Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802-4400, USA.
4
Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802-4400, USA Department of Biology, Texas A & M University, College Station, TX 77843-3258, USA xxwang@scsio.ac.cn.
5
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, PR China xxwang@scsio.ac.cn.

Abstract

For toxin/antitoxin (TA) systems, no toxin has been identified that functions by cleaving DNA. Here, we demonstrate that RalR and RalA of the cryptic prophage rac form a type I TA pair in which the antitoxin RNA is a trans-encoded small RNA with 16 nucleotides of complementarity to the toxin mRNA. We suggest the newly discovered antitoxin gene be named ralA for RalR antitoxin. Toxin RalR functions as a non-specific endonuclease that cleaves methylated and unmethylated DNA. The RNA chaperone Hfq is required for RalA antitoxin activity and appears to stabilize RalA. Also, RalR/RalA is beneficial to the Escherichia coli host for responding to the antibiotic fosfomycin. Hence, our results indicate that cryptic prophage genes can be functionally divergent from their active phage counterparts after integration into the host genome.

PMID:
24748661
PMCID:
PMC4041452
DOI:
10.1093/nar/gku279
[Indexed for MEDLINE]
Free PMC Article
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