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Nanomanipulation of Single RNA Molecules by Optical Tweezers

Nanomanipulation of Single RNA Molecules by Optical Tweezers

Published on: August 20, 2014

The SAM-responsive S(MK) box is a reversible riboswitch.

Angela M Smith¹, Ryan T Fuchs, Frank J Grundy

¹Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.

Molecular Microbiology

|December 15, 2010

Summary

The S(MK) box riboswitch regulates SAM synthetase gene expression by reversibly binding S-adenosylmethionine (SAM). This reversible switch allows rapid cellular response to SAM level fluctuations, modulating translation initiation.

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Area of Science:

Molecular Biology
RNA Biology
Gene Regulation

Background:

The S(MK) box is an S-adenosylmethionine (SAM)-responsive riboswitch in the 5' untranslated region of metK genes.
It regulates SAM synthetase, an enzyme crucial for SAM production in Lactobacillales.

Purpose of the Study:

To investigate the regulatory mechanism of the S(MK) box riboswitch.
To determine if SAM binding to the S(MK) box is reversible and its impact on gene expression.

Main Methods:

In vivo transcript half-life measurements in SAM-depleted Enterococcus faecalis.
In vitro characterization of the SAM-S(MK) box RNA complex half-life.
Fluorescence assays to visualize conformational changes.

Main Results:

S(MK) box riboswitch regulates translation initiation by sequestering the Shine-Dalgarno sequence upon SAM binding.
Transcript half-life showed minimal change in vivo upon SAM depletion, supporting translational control.
In vitro studies indicated shorter RNA complex half-life, suggesting reversible SAM binding.

Conclusions:

The S(MK) box functions as a reversible switch, enabling rapid adaptation to cellular SAM pool variations.
This reversible mechanism allows dynamic modulation of SAM synthetase gene expression.