RNase II levels change according to the growth conditions: characterization of gmr, a new Escherichia coli gene involved in the modulation of RNase II

In Escherichia coli, ribonucleases are effectors that rapidly modulate the levels of mRNAs for adaptation to a changing environment. Factors involved in the regulation of these ribonucleases can be relevant for mRNA stability . RNase II is one of the main ribonucleases responsible for exonucleolytic activity in E. coli extracts. We have identified and characterized a new E. coli gene, which was named gmr (gene modulating RNase II). The results dem onstrate that a deletion of gmr can be associated with changes in RNase II levels and activity. Western analysis and exoribonuclease activity assays s howed a threefold increase in RNase II in the gmr deletion strain. Gmr does not affect RNase II mRNA, but modulates RNase II at the level of protein s tability. RNase II protein turnover is slower in the gmr deletion strain. W e also show that RNase II levels change in different media, and that this r egulation is abolished in a strain lacking gmr. The data presented here sho w that the regulation of ribonucleolytic activity can depend on growth cond itions, and this regulation can be mediated by factors that are not RNases.