Gene targeting is enhanced in human cells overexpressing hRAD51

The ideal therapy for single gene disorders would be repair of the mutated disease genes. Homologous recombination is one of several cellular mechanis ms for the repair of DNA damage. Recombination between exogenous DNA and ho mologous chromosomal loci (gene targeting) can be used to repair an endogen ous gene, but the low efficiency of this process is a serious barrier to it s therapeutic potential. Recent progress in the isolation and characterisat ion of mammalian genes and proteins involved in DNA recombination has raise d the possibility that the cellular biochemistry of recombination can be ma nipulated to improve the efficiency of gene targeting. As an initial test o f this approach, we have overexpressed the gene encoding hRAD51, a protein with homologous DNA pairing and strand exchange activities, in human cells and measured its effect on gene targeting We report a two- to three-fold in crease in gene targeting, and enhanced resistance to ionising radiation in hRAD51-overexpressing cells with no obvious detrimental effects. These obse rvations provide, valuable genetic evidence for the involvement of hRAD51 i n both gene targeting and DNA repair in human cells. Our data also establis h overexpression of recombination genes as a viable approach to improving g ene targeting efficiencies.