Tuning a riboswitch response through structural extension of a pseudoknot

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• RNA folding landscapes are crucial for cellular function and gene regulation.
• Riboswitches control gene expression by binding small molecules.
• The preQ1 class II riboswitch regulates queuosine biosynthesis enzymes.

Purpose of the Study:

• To investigate the folding dynamics of the preQ1 class II riboswitch.
• To understand the role of an extra stem-loop in its 3'-terminal region.
• To elucidate how this structure affects ligand binding and gene regulation.

Main Methods:

• Single-molecule fluorescence energy transfer (smFRET) imaging.
• Analysis of RNA folding dynamics from multiple structural perspectives.
• Investigating ligand-dependent conformational changes.

Main Results:

• The extra stem-loop significantly influences the pseudoknot dynamics of the riboswitch.
• This structure reduces spontaneous folding of the riboswitch.
• It enhances the riboswitch's responsiveness to ligand binding.

Conclusions:

• The extra stem-loop sensitizes the preQ1 class II riboswitch.
• This sensitization broadens the dynamic range of the RNA's ON/OFF regulatory switch.
• The findings provide insights into riboswitch-mediated gene expression control.