Patent ID: 7285538

Claim:
A method of attenuating expression of an endogenous gene of interest in a cell in vitro, said method comprising: a) introducing into the cell a first DNA vector comprising a targeting DNA, wherein said targeting DNA is flanked by a meganuclease site and comprises (1) a DNA homologous to a target site of the endogenous gene of interest and (2) a DNA which attenuates expression of the gene of interest by recombination between said targeting DNA and the gene of interest; and b) introducing into the cell a second DNA vector comprising a coding sequence for a meganuclease, said coding sequence operably linked to expression control sequences permitting production of the meganuclease, said meganuclease cleaving the meganuclease site present in the first DNA vector, thereby increasing the probability of recombination between said targeting DNA and the gene of interest, and thereby increasing the probability of obtaining a cell with the expression of the endogenous gene of interest being attenuated.