Chimeric Nucleases Stimulate Gene Targeting in Human Cells

Correction of gene defects in human somatic cells by targeting as has been used in murine embryonic stem cells (1, 2) has been precluded by the low spontaneous rate of gene targeting (3). However, creation of a DNA double-stranded break (DSB) in the genomic target (DSB-GT) can stimulate homologous recombination by over 1000-fold (4). 
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\nWe can rapidly and quantitatively measure gene targeting by correcting a mutation in a green fluorescent protein (GFP) gene that has been stably integrated into the genome (5) (fig. S1). With an optimized GFP gene targeting system, the introduction of a DSB by I–Sce I (Sce) stimulated GT >40,000-fold and the absolute rate of gene targeting reached 3 to 5% (fig.…