Related Experiment Video
Updated: Aug 2, 2026

An Optimized Protocol for Electrophoretic Mobility Shift Assay Using Infrared Fluorescent Dye-labeled Oligonucleotides
Published on: November 29, 2016
DNA supercoiling and suppression of the leu-500 promoter mutation
Abstract:
top mutations (formerly supX) eliminate DNA topoisomerase I activity and suppress the leu-500 promoter mutation in Salmonella typhimurium (K. M. Overbye, S. K. Basu, and P. Margolin, Cold Spring Harbor Symp. Quant. Biol. 47:785-791, 1983). Sublethal doses of coumermycin which reduce intracellular levels of supercoiling activity in a top mutant eliminated suppression of the leu-500 mutation. This result provides evidence that increased DNA supercoiling suppresses the leu-500 promoter mutation in top mutants.
Related Concept Videos
DNA Topoisomerases
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...
The Eukaryotic Promoter Region
Co-activators and Co-repressors
Epigenetic Regulation
X-chromosome...

