Using the power of genetic suppressors to probe the essential functions of RNase E

This review describes how, using the power of genetic suppressor analysis, mRNA turnover in bacteria was shown to be an essential function of RNase E. RNase E is an essential multifunctional enzyme in bacteria, involved in the processing of stable RNAs to their mature forms (rRNAs and tRNAs) and in the turnover of most mRNAs. Genetic suppressor analysis was successfully used to address whether mRNA turnover is one of the essential functions of RNase E. Conditional lethal mutations in rne were shown to be suppressible by three different classes of extragenic suppressors, including a class that caused overexpression of RelE. The only known function of RelE is the cleavage of mRNA in the ribosomal A-site. Suppression of the conditional lethal defect in rne by RelE overexpression provides strong genetic evidence that mRNA turnover is one of the essential functions of RNase E. Several hypotheses that could explain why mRNA turnover is essential are discussed. Suppressor analysis is an old-fashioned but very powerful approach that can be usefully applied to address a wide variety of important questions in biology and genetics. In this work suppressor analysis has revealed that mRNA turnover is an essential function of RNase E, a conclusion that raises a host of interesting questions for future research.