Biochemistry

Protein (transcription factors and/or transcription cofactors)-binding to DNA is a critical event in regulation of transcription. Electrophoresis Mobility Shift Assay (EMSA), also known as gel shift assay, is a useful tool to detect protein- or protein complex-DNA/RNA interaction and to evaluate DNA binding specificity of transcription factors in vitro. Here we describe a simple method for EMSA with fluorescent dye-bound oligo DNA probes and recombinant protein expressed in bacterial cells. Using fluorescent dye instead of radioisotope enables easy handling and long-term storage of labelled-probes without reduction of detection sensitivity.

In bacteria, interaction of various proteins with DNA is essential for the regulation of specific target gene expression. Electrophoretic mobility shift assay (EMSA) is an in vitro approach allowing for the visualization of these protein-DNA interactions. Rgg proteins comprise a family of transcriptional regulators widespread among the Firmicutes. Some of these proteins function independently to regulate target gene expression, while others have now been demonstrated to function as effectors of cell-to-cell communication, having regulatory activitiesthat that are modulated via direct interaction with small signaling peptides. EMSA analysis can be used to assess DNA binding of either type of Rgg protein. EMSA analysis of Rgg protein activity has facilitated in vitro confirmation of regulatory targets, identification of precise DNA binding sites via DNA probe mutagenesis, and characterization of the mechanism by which some cognate signaling peptides modulate Rgg protein function (e.g. interruption of DNA-binding in some cases).