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Adenosine (A) to inosine (I) RNA editing is widespread in eukaryotes. In prokaryotes, however, A-to-I RNA editing was only reported to occur in tRNAs but not in protein-coding genes. By comparing DNA and RNA sequences of Escherichia coli, we show for the first time that A-to-I editing occurs also in prokaryotic mRNAs and has the potential to affect the translated proteins and cell physiology. We found 15 novel A-to-I editing events, of which 12 occurred within known protein-coding genes where they always recode a tyrosine (TAC) into a cysteine (TGC) codon. Furthermore, we identified the tRNA-specific adenosine deaminase (tadA) as the editing enzyme of all these editing sites, thus making it the first identified RNA editing enzyme that modifies both tRNAs and mRNAs. Interestingly, several of the editing targets are self-killing toxins that belong to evolutionarily conserved toxin-antitoxin pairs. We focused on hokB, a toxin that confers antibiotic tolerance by growth inhibition, as it demonstrated the highest level of such mRNA editing. We identified a correlated mutation pattern between the edited and a DNA hard-coded Cys residue positions in the toxin and demonstrated that RNA editing occurs in hokBin two additional bacterial species. Thus, not only the toxin is evolutionarily conserved but also the editing itself within the toxin is. Finally, we found that RNA editing in hokBincreases as a function of cell density and enhances its toxicity. Our work thus demonstrates the occurrence, regulation, and functional consequences of RNA editing in bacteria.

In the three-dimensional finite element simulation of forging processes, the design of meshes in initial billets, as well as in intermediate remeshing stages, plays the most important role because of the fast mesh degeneracy. In the present paper, a new systematic approach of three-dimensional remeshing, so called modular remeshing, is proposed for the finite element analysis of forging. In order to show the effectiveness of the method, forging of a spur gear is simulated by using several basic modules by the general rigid-plastic finite element code (1, 2, 3) developed for cold forging. The computational results show that the computation can be effectively carried out using the proposed concept of modular remeshing and it can be extended to other more complicated forging processes.