Evaluation of nuclear transfer and transcription of plasmid DNA condensed with protamine by microinjection: The use of a nuclear transfer score

In the present study, the nuclear delivery of a green fluorescence protein (GFP)‐encoding pDNA condensed by protamine was investigated in terms of trans‐gene expression after cytoplasmic ( E (cyt)) and nuclear ( E (nuc)) microinjection. To compare the nuclear transfer process, a novel parameter; the nuclear transfer (NT) score was introduced. The E (cyt) value for protamine/pDNA particles increased in a charge ratio‐dependent manner. The calculated NT score showed that this increase results from an enhancement in nuclear transfer efficiency, which was also quantitatively confirmed by a recently developed confocal image‐assisted three‐dimensionally integrated quantification (CIDIQ) method. Moreover, E (nuc) for protamine/pDNA particles was significantly higher than that for poly‐ l ‐lysine/pDNA particles, suggesting that pDNA, when condensed with protamine, is more accessible to intra‐nuclear transcription. Collectively, protamine is an excellent DNA condenser, with bi‐functional advantages: improvement in nuclear delivery and efficient intra‐nuclear transcription.