Ds. Duan et al., Formation of adeno-associated virus circular genomes is differentially regulated by adenovirus E4 ORF6 and E2a gene expression, J VIROLOGY, 73(1), 1999, pp. 161-169
A central feature of the adeno-associated virus (AAV) latent life cycle is
persistence in the form of both integrated and episomal genomes. However, t
he molecular processes associated with episomal long-term persistence of AA
V genomes are only poorly understood, To investigate these mechanisms, we h
ave utilized a recombinant AAV (rAAV) shuttle vector to identify circular A
AV intermediates from transduced HeLa cells and primary fibroblasts. The un
ique structural features exhibited by these transduction intermediates incl
uded circularized monomer and dimer virus genomes in a head-to tail array,
with associated specific base pair alterations in the 5' viral D sequence.
In HeLa cells, the abundance and stability of AAV circular intermediates we
re augmented by adenovirus expressing the E2a gene product. In the absence
of E2a, adenovirus expressing the E4 open reading frame 6 gene product decr
eased the abundance of AAV circular intermediates, favoring instead the lin
ear replication form monomer (Rf(m)) and dimer (Rf(d)) structures. In summa
ry, the formation of AAV circular intermediates appears to represent a new
pathway for AAV genome conversion, which is consistent with the head-to-tai
l concatemerization associated with latent-phase persistence of rAAV, A bet
ter under standing of this pathway may increase the utility of rAAV vectors
for gene therapy.