PMID:22328678

Citation	Tamura, M, Kers, JA and Cohen, SN (2012) Second site suppression of RNase E essentiality by mutation of the deaD RNA helicase in Escherichia coli.J Bacteriol
Abstract	E. coli cells normally require RNase E activity to propagate and form colonies. Using random Tn10 insertion mutagenesis we screened for second site suppressor mutations that restore colony-forming ability (CFA) to E. coli cells lacking RNase E function, and found mutations in three separate chromosomal loci that had this phenotype. Restoration of CFA by mutations in two of the genes identified was observed only in nutrient-poor medium, whereas the effects of mutation of the ATP dependent RNA helicase DeaD were medium-independent. Suppression of the rne mutant phenotype by inactivation of deaD was partial, as rne/deaD doubly mutant bacteria had a greatly prolonged generation time and grew in liquid media as filamentous chains. Moreover, we found that CFA restoration by deaD inactivation requires normal expression of the endogenous rng gene in the doubly mutant rne/deaD cells. Second site suppression by deaD mutation was attributable specifically to ablation of the helicase activity of DeaD, and was reversed by adventitious expression of RhlE or ribonuclease R, both of which can unwind double strand RNA. Our results suggest a previously unsuspected role for RNA secondary structure as a determinant of RNase E essentiality.
Links	PubMed Online version:10.1128/JB.06652-11
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