Condensation of vector DNA by the chromosomal protein HMG1 results in efficient transfection

The aim of this study was the search for a method of vector packaging using natural chromatin constituents. The interaction of the chromosomal non-histone protein HMG1 with a vector plasmid (pLTEneo) was studied by sedimentation analysis and electron microscopy at physiological salt concentration. At high protein input the complexes exist in a condensed, monodisperse form sedimenting with 80 S irrespective of the supercoiled or relaxed conformation of DNA. Saturation binding is already observed at much lower input ratios. Dilution of 80 S complexes results in decondensation of the complexes. In the decondensed complex form, HMG1 binds in a bead-like manner to specific DNA regions. Condensation by HMG1 is sufficient to introduce the vector into mammalian cells without the need for unphysiological additives. The transfection rates were similar to or even higher than those obtained by the calcium phosphate coprecipitation technique.