Terminal structure of a Densovirus implies a hairpin transfer replication which is similar to the model for AAV.

We cloned the complete sequence of Bombyx DNV (Ina isolate; Bm DNV-1) genome in a bacterial plasmid pUC 119 and determined the nucleotide sequences of both termini, resulting in elucidation of the nucleotide sequence of the complete genomic DNA of DNV. The complete sequence of the DNV DNA (5048 nucleotides) has inverted repeats of 225 nucleotides and the terminal 153 nucleotides are palindromic. The palindromes can fold back on themselves to form a hairpin structure but, unlike AAV, the small internal palindrome which forms a T-shaped conformation was not observed. End-label analysis demonstrated that the palindromic sequences at both termini can exist in either of two orientations (flip or flop) in virion DNA with different frequencies. These data suggest that the hairpin transfer model for AAV replication must be modified to explain the DNV replication. Additionally, a comparison study on the terminal structures of insect, human, and rodent parvoviruses allowed a prediction on the ancestral terminal structure of parvovirus genome.