RESUMO
Gene therapy, the expression in cells of genetic material that has therapeutic activity, holds great promise for the treatment of a number of human diseases. A gene delivery vehicle, or vector, that may be of viral or non-viral origin, is generally used to carry the genetic material. Viral vectors have been developed that exclude immunogenic genes while taking advantage of the genes responsible for proficient integration of the viral genome into that of the host. In this way, viral vectors improve the probability of long-term expression of the therapeutic gene, whereas non-viral vectors, that are not as efficient at introducing and maintaining foreign gene expression, have the advantage of being non-pathogenic and non-immunogenic. Although thousands of patients have been involved in clinical trials for gene therapy, using hundreds of different protocols, true success has been limited. A major limitation of gene therapy approaches, especially when non-viral vectors are used, is the poor efficiency of DNA delivery to the nucleus; a crucial step to ensure ultimate expression of the therapeutic gene product. Here we review existing gene delivery approaches and, in particular, explore the possibility of enhancing non-viral gene delivery to the nucleus by incorporating specific nuclear targeting sequences in vectors, using a range of different strategies.
Assuntos
Núcleo Celular/metabolismo , Técnicas de Transferência de Genes , Animais , Biolística , Transporte Biológico , Membrana Celular/metabolismo , Eletroporação , Endossomos/metabolismo , Marcação de Genes/métodos , Terapia Genética , Vetores Genéticos , Humanos , Lipossomos/química , Membrana Nuclear/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Proteínas Recombinantes de Fusão/genética , Virossomos/genética , Vírus/genéticaRESUMO
Synthesis of the protein components of nuclear chromatin occurs in the cytoplasm, necessitating specific import into the nucleus. Here, we report the binding affinities of the nuclear localisation sequence (NLS)-binding importin subunits for a range of histones and chromatin assembly factors. The results suggest that import of histones to the nucleus may be mediated predominantly by importin beta1, whereas the import of the other components probably relies on the conventional alpha/beta1 import pathway. Differences in recognition by importin beta1 were observed between histone H2A and the variant H2AZ, as well as between histone H3/4 with or without acetylation. The results imply that different histone variants may possess distinct nuclear import properties, with acetylation possibly playing an inhibitory role through NLS masking.
