title: Effect of the Compaction and the Size of DNA on the Nuclear Transfer Efficiency after Microinjection in Synchronized Cells.
abstract: The nuclear transfer process is one of the critical rate-limiting processes in transgene expression. In the present study, we report on the effect of compaction and the size of the DNA molecule on nuclear transfer efficiency by microinjection. A DNA/protamine complex- or variously-sized naked DNA molecules were injected into the cytoplasm or nucleus of synchronized HeLa cells. To evaluate the nuclear transfer process, a nuclear transfer score (NT score), calculated based on transgene expression after cytoplasmic microinjection divided by that after nuclear microinjection, was employed. The compaction of DNA with protamine decreased the NT score in comparison with the injection of naked DNA when the N/P ratio was increased to >2.0. Moreover, when naked DNA was microinjected, gene expression increased in parallel with the size of the DNA in the following order: minicircle DNA (MC07.CMV-EGFP; 2257 bp) > middle-sized plasmid DNA (pBS-EGFP; 3992 bp) > conventional plasmid DNA (pcDNA3.1-EGFP; 6172 bp), while the level of gene expression was quite comparable among them when the DNAs were injected into the nucleus. The above findings suggest that the intrinsic size of the DNA molecule is a major determinant for nuclear entry and that minicircle DNA has a great advantage in nuclear transfer.
authors.affiliation: Faculty of Pharmaceutical Science, Hokkaido University, Kita-12, Nishi-6, Kita-ku, 060-0812 Sapporo, Japan. akita@pharm.hokudai.ac.jp.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Akita
authors.affiliation: Faculty of Pharmaceutical Science, Hokkaido University, Kita-12, Nishi-6, Kita-ku, 060-0812 Sapporo, Japan. dai.kurihara@nipponkayaku.co.jp.
authors.forename: Dai
authors.initials: D
authors.lastname: Kurihara
authors.affiliation: PlasmidFactory GmbH & Co. KG. Meisenstraße 96, D-33607 Bielefeld, Germany. marco.schmeer@plasmidfactory.com.
authors.forename: Marco
authors.initials: M
authors.lastname: Schmeer
authors.affiliation: PlasmidFactory GmbH & Co. KG. Meisenstraße 96, D-33607 Bielefeld, Germany. martin.schleef@plasmidfactory.com.
authors.forename: Martin
authors.initials: M
authors.lastname: Schleef
authors.affiliation: Faculty of Pharmaceutical Science, Hokkaido University, Kita-12, Nishi-6, Kita-ku, 060-0812 Sapporo, Japan. harasima@pharm.hokudai.ac.jp.
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Harashima
keywords: DNA; microinjection; nuclear transfer; size