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J Virol, June 1998, p. 4657-4666, Vol. 72, No. 6
McArdle Laboratory for Cancer Research,
University of Wisconsin Medical School, Madison, Wisconsin 53706
Received 11 December 1997/Accepted 16 February 1998
Replication of the Epstein-Barr viral (EBV) genome occurs once per
cell cycle during latent infection. Similarly, plasmids containing
EBV's plasmid origin of replication, oriP, are replicated once per cell cycle. Replication from oriP requires EBV
nuclear antigen 1 (EBNA-1) in trans; however, its
contributions to this replication are unknown. oriP
contains 24 EBNA-1 binding sites; 20 are located within the family of
repeats, and 4 are found within the dyad symmetry element. The site of
initiation of DNA replication within oriP is at or near the
dyad symmetry element. We have identified a plasmid that contains the
family of repeats but lacks the dyad symmetry element whose replication
can be detected for a limited number of cell cycles. The detection of
short-term replication of this plasmid requires EBNA-1 and can be
inhibited by a dominant-negative inhibitor of EBNA-1. We have
identified two regions within this plasmid which can independently
contribute to this replication in the absence of the dyad symmetry
element of oriP. One region contains native EBV sequences
within the BamHI C fragment of the B95-8 genome of EBV; the
other contains sequences within the simian virus 40 genome. We have
mapped the region contributing to replication within the EBV sequences
to a 298-bp fragment, Rep*. Plasmids which contain three copies of Rep*
plus the family of repeats support replication more efficiently than
those with one copy, consistent with a stochastic model for the
initiation of DNA synthesis. Plasmids with three copies of Rep* also
support long-term replication in the presence of EBNA-1. These
observations together indicate that the latent origin of replication of
EBV is more complex than formerly appreciated; it is a multicomponent
origin of which the dyad symmetry element is one efficient component.
The experimental approach described here could be used to identify
eukaryotic sequences which mediate DNA synthesis, albeit inefficiently.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Rep*: a Viral Element That Can Partially Replace
the Origin of Plasmid DNA Synthesis of Epstein-Barr
Virus
and
*
Corresponding author. Mailing address: McArdle
Laboratory for Cancer Research, University of Wisconsin Medical School,
1400 University Ave., Madison, WI 53706. Phone: (608) 262-6697. Fax: (608) 262-2824. E-mail: sugden{at}oncology.wisc.edu.
Present address: Department of Molecular and Cell Biology, Division
of Genetics, University of California at Berkeley, Berkeley, CA
94720.
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