Bushman and his team made cells that were depleted of LEDGF and found that integration was less frequent in transcription units and in genes regulated by LEDGF. "This implies that LEDGF is part of the machinery that helps dictate the placement of retroviral integration sites within chromosomes," says Bushman.
Bushman notes that finding that LEDGF is part of the cellular apparatus necessary for HIV replication is important to the field of gene therapy. Controlling where gene-therapy vehicles insert in the human genome could help make the delivery of new therapeutic sequences safer. The new findings about LEDGF suggest that engineered tethering interactions might some day allow control over integration site selection during gene therapy. According to Bushman, this finding is of particular importance in light of recent cases where integration of gene-therapy vectors near cancer genes contributed to the development of leukemia in gene-therapy patients.
"This is first example of a cellular factor that's a clear player in target site selection," says Bushman. "This isn't engineering yet, but it's a key piece of information on the way."