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J. Virol., Jan 1998, 420-427, Vol 72, No. 1
P Ward, FB Dean, ME O'Donnell and KI Berns
A basic question in adeno-associated virus (AAV) biology has been whether
adenovirus (Ad) infection provided any function which directly promoted
replication of AAV DNA. Previously in vitro assays for AAV DNA replication,
using linear duplex AAV DNA as the template, uninfected or Ad-infected HeLa
cell extracts, and exogenous AAV Rep protein, demonstrated that Ad
infection provides a direct helper effect for AAV DNA replication. It was
shown that the nature of this helper effect was to increase the
processivity of AAV DNA replication. Left unanswered was the question of
whether this effect was the result of cellular factors whose activity was
enhanced by Ad infection or was the result of direct participation of Ad
proteins in AAV DNA replication. In this report, we show that in the in
vitro assay, enhancement of processivity occurs with the addition of either
the Ad DNA-binding protein (Ad-DBP) or the human single-stranded
DNA-binding protein (replication protein A [RPA]). Clearly Ad-DBP is
present after Ad infection but not before, whereas the cellular level of
RPA is not apparently affected by Ad infection. However, we have not
measured possible modifications of RPA which might occur after Ad infection
and affect AAV DNA replication. When the substrate for replication was an
AAV genome inserted into a plasmid vector, RPA was not an effective
substitute for Ad-DBP. Extracts supplemented with Ad-DBP preferentially
replicated AAV sequences rather than adjacent vector sequences; in
contrast, extracts supplemented with RPA preferentially replicated vector
sequences.
Copyright © 1998, American Society for Microbiology
Role of the adenovirus DNA-binding protein in in vitro adeno-associated virus DNA replication
Department of Microbiology, Hearst Microbiology Research Center, Cornell University Medical College, New York, New York 10021, USA. pjward@mail.med.cornell.edu
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