New recombinases for genome engineering

Site-specific recombinases are a class of proteins that splice different DNA sequences together in a specific and predictable way. They are widely used in biotechnology to manipulate the genomes of plants and animals. A particularly useful application of these proteins is to insert or delete genes or segments of DNA in mammalian chromosomes to study their function. Ideally inserted DNA should be prevented from excising (and excised DNA must be prevented from re-inserting) and this can be done with one group of site-specific recombinases called the serine integrases. One of us, Prof Smith, discovered that the integrase from a bacterial virus, phiC31 can promote an irreversible insertion or deletion without the participation of any other protein. This protein has, as a consequence, become very widely used in nearly all branches of experimental biology. phiC31 integrase is not perfect however and in fact suffers from major problems. Sometimes the reaction promoted by phiC31 integrase is incomplete and sometimes it does not happen at all. Many other serine recombinases have been discovered in the course of genome projects and some may be much better than the original phiC31 integrase for use in biotechnology. Surprisingly these new proteins have never been studied systematically in order to determine whether any of them are in fact better than phiC31 integrase. We would like to do this.