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Department of Microbiology and Tumor Virology Program of the Abramson Comprehensive Cancer Center, University of Pennsylvania, School of Medicine, 201E Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, Pennsylvania 19104
Received 27 July 2006/ Accepted 27 November 2006
Kaposi's
sarcoma-associated herpesvirus (KSHV) persists as episomes in infected
cells by circularizing at the terminal repeats (TRs). The KSHV episome
carries multiple reiterated copies of the terminal repeat, and each
copy is capable of supporting replication. Expression of the
latency-associated nuclear antigen (LANA) is critical for the
replication of TR-containing plasmids. A 32-bp sequence upstream of
LANA binding site 1 (LBS1), referred to as RE (replication element),
along with LANA binding sites 1 and 2 (RE-LBS1/2), is sufficient to
support replication (J. Hu and R. Renne, J. Virol.
79:2637-2642, 2005). In this report we demonstrate that the
minimal replicator element (RE-LBS1/2) replicates in synchrony with the
host cellular DNA, and only once, in a cell-cycle-dependent
manner. Overexpression of the mammalian replication inhibitor geminin
blocked replication of the plasmid containing the minimal replicator
element, confirming the involvement of the host cellular replication
control mechanism, and prevented rereplication of the plasmid in the
same cell cycle. Overexpression of Cdt1 also rescued the replicative
ability of the RE-LBS1/2-containing plasmids. A chromatin
immunoprecipitation assay performed using anti-origin recognition
complex 2 (
-ORC2) and
-LANA antibodies from cells
transfected with RE-LBS1/2, RE-LBS1, LBS1, or RE showed the association
of ORC2 with the RE region. Expression of LANA increased the number
of copies of chromatin-bound DNA of replication elements,
suggesting that LANA is important for the recruitment of ORCs and may
contribute to the stabilization of the replication protein complexes at
the RE
site.
Published ahead of print on 6 December 2006.
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