Alternatively, the covalent attachment of the replication protein to the end of the nicked DNA might present an opportunity for a gene therapy approach. While the use of RNA decoys for the selective inhibition of HIV replication has been explored, these attempts rely on overexpression of molecules which competitively compete for binding to viral or cellular trans-acting factors. 16 Such a decoy might consist of a molecule mimicking the viral stem loop structure to such an extent that the strand nicking reaction takes place. Idealized representation of possible circovirus replication scheme and mechanism of action for DNA decoy. In the usual infectious cycle, the replication protein covalently attaches to the viral DNA within the loop sequence through an ATP-dependent strand breakage reaction.
Replication proceeds with the help of host-derived DNA polymerase.
In the inhibited cycle, the DNA decoy provides an alternate substrate for the strand cleavage reaction, in which the replication protein becomes covalently attached to the decoy. Because the decoy cannot serve as a functional template for the complete synthesis cycle, it remains irreversibly attached to the replication protein and prevents its participation in subsequent rounds of replication. In order for this scheme to work, several obvious technical problems must be solved. However, these obstacles are not insurmountable. Engineered sequence and structural modifications or even alternate structural chemistries could also make such molecules less susceptible to endonucleolytic degradation.