Mechanism of regulation of E. coli cell duplication by DNA-, RNA- binding protein Hfq

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FepA and FhuE proteins involved in iron transport in the outer-membrane were overproduced in the hfq::cat mutant cells. The hfq::cat mutant was more susceptible to killing by hydrogen peroxide, probably due to the excess incorporation of iron. Direct measurement of intracellular iron concentrations by electroparamagnetic resonance spectroscopy revealed that the mutant cells indeed accumulated significantly higher levels of iron than the wild type cells. The Hfq protein protected DNA from iron-induced oxidative damages in vitro. These results suggest that the Hfq protein is involved in the mechanism of cell survival by protecting cells from oxidative stress.Genetic interaction between hfq and RNazes was examined. Temperature sensitivity of the ams-1 (RNaze E^<ts>) mutant strain was suppressed by introduction of the hfq::cat mutation. Its suppression was cancelled by introduction of mg::cat (RNaze G defective) mutation. These results suggest that the Hfq protein is involved in the mechanism of regulation of mRNA stability by RNaze E and RNaze G.