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

Area of Science:

• Molecular Biology
• Virology
• Archaea Research

Background:

• Archaea are infected by viruses, some integrating their genomes into the host.
• SSV-type integrases are a unique class of archaeal tyrosine recombinases mediating this integration.
• Understanding the molecular mechanisms of archaeal viral integration is limited by a lack of in vitro systems.

Purpose of the Study:

• To establish an in vitro assay for SSV2 integrase (Int(SSV2)) activity.
• To investigate the roles of different enzyme domains and DNA sequences in recombination.
• To provide mechanistic insights into archaeal viral DNA recombination.

Main Methods:

• Development of an in vitro integration/excision assay for SSV2 integrase.
• Characterization of minimal DNA sequence requirements for recombination.
• Analysis of enzyme structure-function relationships using full-length and truncated integrase.

Main Results:

• SSV2 integrase alone efficiently catalyzes both integration and excision in vitro.
• A 27-bp specific DNA sequence is essential, with flanking sequences influencing efficiency.
• Distinct enzyme domains are responsible for tetramer formation, DNA binding, and catalysis.

Conclusions:

• SSV-type integrases can independently mediate viral DNA recombination with host genomes.
• The study elucidates the domain organization and functional roles within SSV2 integrase.
• Mechanistic insights into a simple, reversible recombination process catalyzed by an archaeal integrase are provided.