The Impact of mRNA Structures Regulating Transcription Attenuation on Bacterial Fitness

Abstract

In bacteria regulation of transcription attenuation through modulations in mRNA structure is a common mechanism for coordinating gene expression. The formation of rho‐independent transcription terminators may be controlled by variety of factors including direct interactions with small molecules, tRNAs, and proteins. However, generally such mRNA structures are one part of several regulatory layers that include regulation of transcription initiation and in many cases appear to act as fine‐tuning mechanisms. The role such mRNA structures play in organism fitness and the forces that maintain their presence in microbial genomes remain largely undetermined. In this work we examine this question by assessing the impact of disrupting the protein‐binding site within an mRNA structure that regulates ribosomal proteins L20 and L35 in Bacillus subtilis. The mutation prevents formation of a rho‐independent terminator that allows autoregulation in response to ribosomal protein L20, but otherwise has minimal effects on gene expression. B. subtilis carrying the altered RNA display a cold‐sensitive increase in lag‐time, but the mutation has little effect on logarithmic phase growth rate. Our findings suggest that such RNA regulators may be most important within a rapidly changing environment and at the transitions between growth phases.