Using the epigenetic code to promote the unpackaging and transcriptional activation of DNA polyplexes for gene delivery.

Nonviral gene delivery has seen limited clinical application due in part to the inefficiency with which most nonviral vehicles navigate the intracellular gene delivery pathway. One key problem is the inability of most DNA-packaging materials to release DNA and enable its efficient transcription. Thus, our aim was to develop gene delivery polyplexes capable of initiating their own transcription upon arrival in the nucleus. We created nuclease-resistant polyplexes with plasmid DNA (pDNA) and post-translationally modified histone 3 (H3K4Me3) tail peptides known to signal transcriptional activation on chromosomal DNA. When the H3K4Me3-pDNA polyplexes were directly microinjected into the nuclei of NIH/3T3 mouse fibroblasts, protein expression occurred earlier and in a greater fraction of cells than when polyethylenimine-pDNA polyplexes were microinjected. The rate of protein expression initiated by the H3K4Me3-pDNA polyplexes was also significantly accelerated in comparison with the rate initiated by non-trimethylated H3-pDNA polyplexes. These differences in protein expression rates were quantified by the development of a noncompartmentalized cellular kinetics model. These results highlight the importance of polyplex unpackaging as a gene delivery barrier, and demonstrate for the first time that the epigenetic code can be utilized in nonviral gene delivery.