From left, Mike Karberg, Alan Lambowitz, and Huatao Guo
primarily responsible for recognizing the target DNA. Lambowitz and his colleagues have varied the 14-nucleotide site to recognize many different human and bacterial genes. Bruce Sullenger, associate professor of experimental surgery at Duke University Medical Center, and his colleagues tested whether intron insertion could be carried out in mammalian cells by using lipid vesicles called liposomes to deliver CCR5, a human gene involved in HIV transmission, and a modified intron into cells. PCR analysis of DNA isolated from the mammalian cells showed that the intron had inserted into CCR5, indicating that the mammalian cellular machinery could support this mechanism. Though retargeted group II introns integrate efficiently into chromosomal genes in bacteria, the next step is integrating modified introns into a chromosomal gene in a human cell. "Relatively few people have studied these introns, and not too many were familiar with them. We worked on this as a basic research project ... so the practical application is exciting," says Lambowitz.
--Nadia S. Halim