Extremely low levels of "leaky" expression of genes in bacterial protein expression systems can severely curtail cell viability when expressed proteins are toxic. A general method for sensitive detection of such expression is lacking. Here, we present a method based on microscopic visualization of a fluorescent "reporter" protein (RFP-HU-A) constructed by fusing red fluorescent protein (RFP) to the N-terminus of a nucleoid-associated, histone-like DNA-binding protein, HU-A. Localization of RFP-HU-A within nucleoids facilitates detection, quantitation, and characterization of leaky expression at the single-cell level.
Keywords: Bacterial nucleoid staining; Fluorescence imaging; Fluorescent HU; Gene expression; Leaky repression; Negative regulation.
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