Intracellular compartmentalization of DNA fragments in cultured airway epithelial cells mediated by cationic lipids

Purpose. The amount and intracellular distribution of DNA fragments (491-bp ) was characterized after transfection in vitro with a commercially availab le cationic lipid. Localization of fragment to the nucleus, its subcellular distribution, and integrity within the cells was determined for various ti mes after transfection. Methods. Cystic fibrosis (CF) airway epithelial cells were transfected with P-32 and FITC labeled single-stranded (ss) or double-stranded (ds) DNA fra gments complexed with Lipofectamine(R) at various charge ratios. Results. A 5/1 (+/-) charge ratio was found to be the optimal ratio for tra nsfection of both se-and dsDNA. After a 5 h exposure, 7.51 +/- 0.89% of the radioactivity was associated with the nuclear fraction whereas only 1.07 /- 0.23%, was found in the nuclear fraction when dsDNA was used. The nuclea r radioactivity detected after a 24 h exposure was only 1/3 of that after 5 h. Analysis of fragment stability in the cytosolic and nuclear fractions s howed the presence of intact fragment in each subcellular compartment. No i ntranuclear/intracellular fragment could be detected in control experiments with naked DNA. Conclusions. The results from these experiments indicate that small fragmen ts of DNA can be efficiently and rapidly transferred intact to the cell nuc leus using cationic lipids and that ssDNA fragments are more effective than dsDNA fragments for nuclear delivery.