RESCUE AND REPLICATION SIGNALS OF THE ADENOASSOCIATED VIRUS-2 GENOME

The adeno-associated virus 2 (AAV) genome is a single-stranded DNA whi ch contains the inverted terminal repeats (ITRs) of 145 nucleotides. T he terminal 125 nucleotides of each ITR form palindromic hairpin struc tures that serve as primers for AAV DNA replication. These hairpin str uctures also play a crucial role in the integration, as well as the re scue, of the proviral genome from latently-infected cells, or from the recombinant AAV plasmids. However, the ITRs also contain an additiona l domain, designated the D-sequence, a 20-nucleotide stretch that is n ot involved in the formation of hairpins. In order to examine the role of the D-sequence in viral DNA rescue and replication, a number of re combinant AAV plasmids were constructed which contained deletions/subs titutions in different regions of the ITRs. The results presented here reveal the existence of additional sequences, other than the hairpin structures, which serve as primers for AAV DNA replication. The result s also show that whereas the hairpin structures are sufficient for exc ision and replication of the viral DNA, the D-sequence is crucial for the high efficiency of rescue and replication of the AAV genome. (C) 1 995 Academic Press Limited