The Champoux lab studies retroviral replication with a focus on HIV-1, the causative agent of AIDS, and Moloney murine leukemia virus, a retrovirus that causes thymic lymphomas. One aspect of this work focuses on how the DNA polymerase activity of reverse transcriptase carries out displacement synthesis, an activity that is required for the production of the long terminal repeats on the ends of the viral DNA. Another interest is the RNase H activity of reverse transcriptase that not only degrades the viral RNA after minus-strand synthesis, but also produces the primer RNA for initiating plus-strand synthesis and removes RNA primers once they have been extended. Current studies also focus on the recent finding that the RNase H activity has a preference for certain nucleotides in the vicinity of a cleavage site. The structural features of reverse transcriptase that are important for each of these reactions are being examined using both genetic and biochemical approaches. Finally, the mechanism of copy choice recombination during reverse transcription is also being investigated. The long term goal of these projects is to understand the details of reverse transcription with an eye towards developing new anti-retroviral therapies.