Elevation of RNase R in Response to Multiple Stress Conditions

Chenglu Chen,Murray P Deutscher

doi:10.1074/jbc.c500333200

Abstract

Cells respond to adverse environmental conditions by synthesizing new proteins or elevating the levels of pre-existing ones that are needed to cope with the particular stress situation. We show here that Escherichia coli RNase R, a processive 3'-to5'-exoribonuclease, is dramatically increased in response to a variety of different stress conditions. Elevation of RNase R activity by as much as 10-fold was observed in response to entry into stationary phase, starvation, and cold shock, and a approximately 3-fold increase was seen during growth in minimal medium compared with rich medium. The elevation in RNase R activity was associated primarily with an increase in RNase R protein. RNase R was previously implicated in quality control of rRNA and tRNA and in the decay of mRNAs with extensive secondary structure. Its dramatic increase under multiple stress conditions suggests extensive remodeling of structured RNA in response to the altered environment.

Highlights

The ability to sense and adapt to environmental change is critical to the survival of bacteria
RNase R Levels during Growth—As an initial assessment of whether RNase R might be subject to regulation, we determined its activity as cells progressed from exponential phase through late stationary phase
In the representative experiment shown, RNase R activity, which remains relatively constant during exponential phase, increases ϳ6-fold as the culture approaches stationary phase and increases an additional 2-fold during an extended stationary phase

Summary

Elevation of RNase R in Response to Multiple Stress Conditions*

Its dramatic increase under multiple stress conditions suggests extensive remodeling of structured RNA in response to the altered environment. Upon encountering stress conditions, cells must rapidly alter their gene expression and remodel their RNA complement to deal with the changing environment. As a consequence, both new RNA transcription as well as RNA degradation must take place. A similar response to one of these stresses, cold shock, was recently reported [8] These data indicate that RNase R is novel among E. coli RNases and suggest that its action on structured RNAs may play an important role in helping cells cope with a changing environment

EXPERIMENTAL PROCEDURES

RESULTS

Relative RNase R specific activitya

DISCUSSION

Effect of starvation on RNase R activity

RNase RϪ