Site-Specific Recombination by SSV2 Integrase: Substrate Requirement and Domain Functions.

Archaea are host to a variety of viruses. A number of archaeal viruses are able to integrate their genome into the host genome. Many known archaeal viral integrases belong to a unique type, or the SSV type, of tyrosine recombinases. SSV-type integrases catalyze viral integration into and excision from a specific site on the host genome. However, the molecular details of the recombination process have yet to be fully understood because of the lack of an established in vitro recombination assay system. Here we report an in vitro assay for integration and excision by SSV2 integrase, a member of the SSV-type integrases. We show that SSV2 integrase alone is able to catalyze both integration and excision and reveal how different parts of the target DNA and the enzyme serve their roles in these processes. Therefore, our results provide mechanistic insights into a simple recombination process catalyzed by an archaeal integrase.