Both attenuation of the trp operon in E. coli and riboswitches in B. subtilis rely on changes in the secondary structure of the leader regions of mRNA to regulate gene expression. Compare and contrast the specific mechanisms in these two types of regulation with that involving short noncoding RNAs (sRNAs).

Key Concepts

Attenuation in the trp operon

Attenuation is a regulatory mechanism in the trp operon of E. coli that controls gene expression based on tryptophan levels. It involves the formation of different secondary structures in the mRNA leader sequence, which can either promote or inhibit transcription. When tryptophan is abundant, a structure that terminates transcription is favored, while low levels allow for a structure that permits transcription to continue.

Riboswitches in B. subtilis

Riboswitches are segments of mRNA that can change their secondary structure in response to specific metabolites, thereby regulating gene expression. In B. subtilis, the binding of a metabolite to the riboswitch can lead to the formation of a structure that either sequesters the ribosome binding site or promotes transcription termination, effectively controlling the synthesis of proteins based on the cellular environment.

Short noncoding RNAs (sRNAs)

Short noncoding RNAs (sRNAs) are regulatory RNA molecules that can modulate gene expression by base-pairing with target mRNAs. They often influence the stability and translation of mRNAs by altering their secondary structures or by recruiting proteins that affect mRNA degradation. Unlike attenuation and riboswitches, which are intrinsic to the mRNA itself, sRNAs act as trans-acting factors that can regulate multiple targets.