Picking the Right Spot

Retroviruses ensure that their reverse-transcribed RNA genomes are integrated into the DNA of host cells, a characteristic that has prompted their use as gene-therapy vectors. In a Perspective, Trono discusses new findings ( Wu et al .) that describe how two retroviruses, MLV and HIV, show very different sites of integration in the human genome. Trono explains the important implications of these findings for the use of retroviral vectors in gene therapy.