Characterization of Five Purine Riboswitches in Cellular and Cell-Free Expression Systems

Area of Science:

• Microbiology
• Molecular Biology
• Gene Regulation

Background:

• Bacillus subtilis utilizes five purine riboswitches to regulate purine synthesis and transport transcriptionally.
• Riboswitches consist of conserved aptamers and variable expression platforms with transcription terminators.

Purpose of the Study:

• To characterize the function of all five purine riboswitches in Bacillus subtilis during active gene expression.
• To investigate the interplay between transcription pausing, metabolite concentration, and gene expression control.

Main Methods:

• In vitro transcription assays to assess readthrough and metabolite-dependent activity.
• In vivo gene expression studies to observe riboswitch dynamics.
• Identification of transcription pause sites within riboswitch expression platforms.

Main Results:

• Transcription pause sites were identified upstream of terminators in all five purine riboswitches.
• A correlation was established between in vitro transcription readthrough and in vivo gene expression levels.
• Riboswitches demonstrated metabolite sensitivity in the micromolar concentration range.
• Dynamic control of gene expression by individual riboswitches was observed in vivo.

Conclusions:

• The study elucidates the regulatory mechanisms of Bacillus subtilis purine riboswitches.
• Identified pause sites and correlated in vitro/in vivo data provide a deeper mechanistic understanding.
• These findings contribute to the knowledge of purine metabolism regulation at the transcriptional level.