BINDING OF CATIONIC ALPHA-HELICAL PEPTIDES TO PLASMID DNA AND THEIR GENE-TRANSFER ABILITIES INTO CELLS

Polycationic reagents such as cationic lipids and poly-L-lysine are wi dely used for gene transfer into cells in vitro and show promise as ve ctors for in vivo gene therapy applications as nonviral gene transfer techniques, We have developed a novel transfection method using cation ic amphiphilic alpha-helical oligopeptides with repeated sequences, Ol igopeptide has the advantages of being easily designed and modified be cause of its simple structure, In this study, we synthesized five kind s of peptides of which the total chain length and the width of the hyd rophobic region were changed. The binding of the peptides to plasmid D NA was evaluated by agarose gel electrophoresis, It was found that the long and/or hydrophobic peptides can strongly bind to the DNA, The fo rmation of large aggregates with a 0.5-5-mu m diameter, which consiste d of the long peptides and the DNA, was observed by electron microscop y. The transfection abilities of the peptides were determined by the e xpression of luciferase from its cDNA in COS-7 cells, The long peptide s showed high transfection abilities. As: a result, it could be said t hat the transfection ability of these peptides was parallel to their a bility to form aggregates with DNA, Furthermore, the transfection abil ity was increased by the addition of chloroquine in the transfection p rocedure, This result indicated that aggregates would be mediated by t he endocytosis pathway.