title: Competitive inhibition of natural antisense Sok-RNA interactions activates Hok-mediated cell killing in Escherichia coli.
abstract: Short regulatory RNAs are widespread in bacteria, and many function through antisense recognition of mRNA. Among the best studied antisense transcripts are RNA antitoxins that repress toxin mRNA translation. The hok/sok locus of plasmid R1 from Escherichia coli is an established model for RNA antitoxin action. Base-pairing between hok mRNA and Sok-antisense-RNA increases plasmid maintenance through post-segregational-killing of plasmid-free progeny cells. To test the model and the idea that sequestration of Sok-RNA activity could provide a novel antimicrobial strategy, we designed anti Sok peptide nucleic acid (PNA) oligomers that, according to the model, would act as competitive inhibitors of hok mRNA::Sok-RNA interactions. In hok/sok-carrying cells, anti Sok PNAs were more bactericidal than rifampicin. Also, anti Sok PNAs induced ghost cell morphology and an accumulation of mature hok mRNA, consistent with cell killing through synthesis of Hok protein. The results support the sense/antisense model for hok mRNA repression by Sok-RNA and demonstrate that antisense agents can be used to out-compete RNA::RNA interactions in bacteria. Finally, BLAST analyses of approximately 200 prokaryotic genomes revealed that many enteric bacteria have multiple hok/sok homologous and analogous RNA-regulated toxin-antitoxin loci. Therefore, it is possible to activate suicide in bacteria by targeting antitoxins.
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institutet, Berzelius väg 35, 171 77, Stockholm, Sweden.
authors.forename: Omid R
authors.initials: OR
authors.lastname: Faridani
authors.forename: Abbas
authors.initials: A
authors.lastname: Nikravesh
authors.forename: Deo Prakash
authors.initials: DP
authors.lastname: Pandey
authors.forename: Kenn
authors.initials: K
authors.lastname: Gerdes
authors.forename: Liam
authors.initials: L
authors.lastname: Good
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000235:genetics* / Q000378:metabolism; D001667:Binding, Competitive; D004755:Enterobacteriaceae / Q000235:genetics; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D020135:Peptide Nucleic Acids / Q000737:chemistry / Q000494:pharmacology*; D012313:RNA / Q000037:antagonists & inhibitors* / Q000235:genetics; D016372:RNA, Antisense / Q000037:antagonists & inhibitors* / Q000502:physiology; D012329:RNA, Bacterial; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; C087025:Hok protein, E coli; D020135:Peptide Nucleic Acids; D016372:RNA, Antisense; D012329:RNA, Bacterial; D012333:RNA, Messenger; C087026:Sok antisense RNA, E coli; D012313:RNA