DNA-REPLICATION IN THE AUTONOMOUS PARVOVIRUSES

Both ends of the linear single-stranded parvoviral DNA genome contain short palindromic sequences which form duplex hairpins containing cis- acting information required for replication and encapsidation. DNA syn thesis is primed directly by the 3' end, and genomes are replicated th rough multimeric duplex intermediates by unidirectional, leading-stran d synthesis. Unit-length genomes are excised from these concatemers, a nd their telomeres replicated, by the viral NS1 protein, which introdu ces a single-strand nick into specific origin sequences, becoming cova lently attached to the 5' end at the nick and providing a 3' hydroxyl which primes synthesis of a new copy of the telomere. Progeny DNA synt hesis requires ongoing replication and is dependent upon packaging.