Gene acquisition by large DNA viruses

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Background - Large DNA viruses encode genes that seem to have come from cellular organisms. These have probably been acquired from their hosts as the different viruses and the organisms they infect have co-evolved over billions of years. For example, myxoma virus encodes an enzyme that protects these insect-vectored poxviruses from UV-light. The closest similar proteins are encoded in plants and insects. Where do these virus genes come from and how did they get there? We hope to find answers to this question.      "Genetic recombination" is a term used to describe the swapping and joining of different DNAs and it creates organisms with new biological properties. We've studied how poxviruses recombine DNA and this has produced commercial tools for cloning DNA and genetically-engineering viruses. We've tested how much similarity is needed for recombination between vaccinia virus (VAC) and input DNA and while there is less DNA swapping as the resemblance decreases, it doesn't drop to zero with unrelated DNAs. We've sequenced 17 VAC clones that have captured DNA bearing no resemblance to the virus DNA. These viruses exhibit complex gene rearrangements near random integration sites.      I propose that this process offers a route by which large DNA viruses can capture copies of host genes. The process could simply involve end-to-end joining of DNA fragments or might use a mechanism related to the movement of retroviruses and retrotransposons. The latter scheme has an advantage in that it can prune the gene copy (remove introns) in a way that would enable virus expression. Aims - there are three aims Transfection/mapping. We'll transfect DNA encoding a drug-selectable reporter protein into VAC-infected cells, and then isolate and sequence the resulting recombinants. These studies will determine where the DNA goes and how the virus genome is altered by these events. Double-stranded breaks. We'll introduce double-stranded breaks into replicating VAC DNA and then test if this increases the yield of viruses that have captured a reporter gene. Such studies will better define the steps underpinning DNA capture. Retroviruses/retrotransposons. Retrotransposition reactions copy RNA into DNA and then insert the copied DNA into a new site in the genome. We'll test whether reporter genes can be "retroposed" into VAC using either the proteins that catalyze movement of human LINE 1 retrotransposons or as genes packaged into retrovirus particles. Training - Trainees will acquire highly-desirable skills studying genomics, virology and molecular biology in a stimulating academic environment supported by advanced infrastructure. Conclusions - It is unknown how large DNA viruses capture genes from cellular hosts, but the process could play a key role in creating new viruses with novel properties. This work will provide original insights into the process(es) responsible for this fascinating feature of virus biology and offer HQP outstanding training in biotechnology.