Improvement of exogenous DNA nuclear importation by nuclear localization signal‐bearing vectors: a promising way for non‐viral gene therapy?

Abstract

Several vectors have been developed in order to target genes to specific cells. Virus-based vectors lead to a high transfection efficiency in vitro, but display important disadvantages such as pathological risks, which they expose to patients. Plasmid-associated chemical vectors lack these disadvantages, but allow only a very low efficiency of transgene expression. Most of the non-viral-based gene transfer techniques developed until now mainly focused their efforts to overcome the problem of DNA entry into the cell. Some recent works, however, have begun to investigate the nucleus entry problem and suggest that the trafficking of DNA from cytosol to the nucleus may be improved by using the nuclear localization signal (NLS) found in some nuclear proteins. If the vector contains one or several NLS, either as covalently or non-covalently DNA-linked peptides, a competition may take place between the rate of dissociation of the DNA-vector complexes and the rate of loading of the complexes to the NLS-mediated nucleus importation machinery. This equilibrium may be displaced towards the importation pathway by the use of NLS-bearing proteins instead of peptides. The possibility of recruiting normal endogenous cellular pathways of nuclear uptake to promote entry of exogenously applied DNA through the nuclear pore complex would, thus, seem promising. Nevertheless, attempts to improve the transport of DNA to the nucleus through the use of NLSs have achieved limited success. Although these systems show improved transgene expression, little is known about how they function in transfected cells, and the optimal formulation for gene expression is yet to be determined.

Delivery of Nucleic Acids for Cancer Gene therapy: Overcoming extra- and intra-cellular Barriers

“…The nuclear envelope is a bilayer which protects the contents of, and tightly controls entry into the nucleus through the action of the nuclear pore complex (NPC) [104]. Passive entry into the nucleus is restricted to molecules less than 10 nm in diameter, which excludes the entry of DNA, and is the final barrier that needs to be overcome for successful DNA delivery.…”

Using inositol as a biocompatible ligand for efficient transgene expression

“…61 In general, current gene vectors lack the ability to locate in cell nuclei, and it was deemed that nuclear import of therapeutic DNA or RNA occurred after they were released from the PEI transgene systems. [62][63][64] …”

“…Therefore, researchers are currently interested in investigating cationic gene vectors that can locate in cell nuclei. 29,63,64 Using PG6-PEI25k as the platform, the ability of the PG6-PEI-INO polymers to enter cell nuclei and to mediate efficient transgene expression was found to increase with their INO moiety numbers, as reported by fluorescent tracking and EGFP expression. Therefore, the INO might be a potential ligand for efficient transgene expression.…”

DNA gel particles: An overview

“…In the absence of cell division, and additional limiting step is the translocation of DNA through the nuclear envelope. Some recent works have turned to investigate the nucleus entry problem [119]. Evidently nuclear pore complexes (NPC) act as gateway for macromolecular traffic between the cytoplasm and the nucleus.…”