Overall interaction of cytosolic proteins with the PEI/DNA complex

Little is known on mechanisms involved in transport of complex of DNA and gene carrier molecules from the cytosol to the nucleus. We aimed to identify cytosolic proteins interacting with the polyethylenimine (PEI)/DNA complex, using 2-D gel electrophoresis and peptide mass fingerprinting. Fifteen proteins including actin, beta-tubulin, and other metabolic proteins were identified. They demonstrated various molecular weights and isoelectric points, and were categorized into 3 groups: early binding, late binding, and transient binding proteins. Protein binding caused DNA release from the PEI/DNA complex with a cation/anion (C/A) ratio of 2, where complex formation was weak. Knowledge on interactions between cytosolic proteins and DNA/carrier complexes will help understand intracellular gene delivery mechanisms.