Asymmetric replication in vitro from a human sequence element is dependent on adeno-associated virus Rep protein

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Adeno-associated virus type 2 (AAV) DNA exhibits preferential integration into human chromosome 19.
• The precise mechanism of this targeted DNA integration has remained largely unknown.
• AAV nonstructural Rep proteins (Rep68/Rep78) bind to specific DNA sequences in both the viral genome and the integration site.

Purpose of the Study:

• To elucidate the mechanism by which AAV DNA targets specific integration sites.
• To investigate the role of AAV Rep proteins in the targeted integration process.
• To characterize the DNA replication activities of Rep proteins at the AAV integration locus.

Main Methods:

• Utilized a cell-free replication assay with a cloned human chromosome 19 integration site subfragment (P1).
• Assessed the impact of recombinant AAV Rep proteins on DNA replication in vitro.
• Analyzed DNA replication patterns and protein-DNA interactions.

Main Results:

• Rep protein binding to the P1 sequence is crucial for targeted integration.
• Rep proteins induce extensive, asymmetric DNA replication of linear or open-circular DNA templates containing the P1 sequence.
• Replication initiation involves sequence-specific nicking by Rep, forming a covalent Rep-DNA adduct, similar to its activity at AAV inverted terminal repeats.

Conclusions:

• AAV-mediated targeted DNA integration involves a complex process of limited DNA replication and rearrangements facilitated by Rep proteins.
• The Rep proteins' DNA replication and nicking activities at the P1 locus are key to the mechanism of targeted integration.
• Understanding this mechanism provides insight into viral DNA integration and potential therapeutic applications.