Binding of RNase R to ribosomes: comparison of non‐stop mRNA and REP sequence‐containing message (748.2)

Abstract

RNase R, a 3' to 5' exoribonuclease able to act on most RNAs including those with extensive secondary structure, is subject to a complex regulatory mechanism. Most RNase R in exponential phase cells is sequestered on ribosomes, where it is stable. In contrast, the free form of the enzyme is turned over rapidly, presumably because it is deleterious to cells due to its promiscuous action on essential RNA molecules. We previously showed that RNase R binding to ribosomes is stimulated by non‐stop mRNA leading to its participation in trans‐translation. We show here that RNase R binding to ribosomes is also stimulated by messages containing intergenic REP sequences suggesting that degradation of these messages utilizes a similar mechanism to non‐stop mRNA decay. Interestingly, the stimulation of RNase R binding is lost when the REP sequence is moved further away from the translation termination codon and the amount of protein produced from the message is elevated. These data show that as with non‐stop mRNA, other messages which result in ribosome stalling prior to normal termination also lead to RNase R binding and likely the induction of trans‐translation.Grant Funding Source: Supported by National Institutes of Health Grant GM16317