Biophysical studies of recombinant chromatin and nucleosome core particle (NCP) systems interacting with lipids.

Abstract

The self-assembling aggregates of liposomes and model chromatin were characterized using small angle X-ray scattering (SAXS), and a number of optical microscopy techniques. The cationic and anionic liposomes of different surface charge density were prepared from the mixtures of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with either 1,2-dioleoyl-3-trimethylammonium-propane chloride salt (DOTAP) or 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) sodium salt (DOPG), respectively. The nucleosome core particles (NCP) and nucleosome arrays were reconstituted from recombinant DNA and histone proteins and used as chromatin models.

The supramolecular organization of cationic chromatin - liposome aggregates was found to be controlled by the bilayer surface charge density and related to the stability of chromatin. In contrast to the cationic liposomes, the chromatin remained stable in the aggregates with anionic liposomes over a whole range of charge densities.

Our results on the chromatin interactions with cationic liposomes are relevant in the field of the nonviral gene delivery not only for the intracellular delivery of chromatin by lipoplexes, but also in the research on the DNA-lipid-protein/peptide aggregates. The results on the aggregates of chromatin with the anionic liposomes are relevant for the understanding of the chromosomal interactions with the nuclear envelope and nuclear lipids of eukaryotic cells.