Initiation of mRNA decay in Bacillus subtilis

Ribosome stalling in the leader region of ermC mRNA results in a 10–15‐fold increase in ermC mRNA half‐life in Bacillus subtilis. Fusion of the ermC 5′ regulatory region to several B. subtilis coding sequences resulted in induced stability of the fusion RNAs, showing that the ermC 5′ region acts as a general ‘5′ stabilizer’. RNA products of an ermC–lacZ transcriptional fusion were inducibly stable in the complete absence of translation and included a small RNA that is likely to be a decay product arising by blockage of a 3′‐to‐5′ exoribonuclease activity. Insertion of sequences that encode endonucleolytic cleavage sites into the ermC coding sequence resulted in cleavage products whose stability depended on the nature of their 5′ and 3′ ends. It can be concluded from this study that initiation of mRNA decay in B. subtilis generally occurs at or near the 5′ terminus.