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Journal of Virology, September 2000, p. 8563-8574, Vol. 74, No. 18
Department of Cell Biology, Albert Einstein
College of Medicine, Bronx, New York 10461,1 and
Department of Cancer Genetics, Roswell Park Cancer Institute,
Buffalo, New York 142632
Received 14 February 2000/Accepted 20 June 2000
The 165-kb circularized chromosome of Epstein-Barr virus (EBV) is
replicated in latently infected cells once per cell cycle by host
proteins during S phase. Replication initiates at multiple sites on
latent EBV chromosomes, including within a 1.8-kb region called
oriP, which can provide both replication and stabilization for recombinant plasmids in the presence of the EBV-encoded protein, EBNA-1. Replication initiates at or near the dyad symmetry component (DS) of oriP, which depends on multiple EBNA-1 binding
sites for activity. To test the importance of the replication function
of oriP, the DS was deleted from the viral genome. EBV
mutants lacking the DS and carrying a selectable gene could establish
latent infections in BL30 cells, in which circular, mutant viral
chromosomes were stably maintained. Analysis of replication fork
movement using two-dimensional gel electrophoresis showed that the
deletion of the DS reduced the initiation events to an undetectable
level within the oriP region so that this segment was
replicated exclusively by forks entering the region from either
direction. A significant slowing or stalling of replication forks that
occurs normally at the approximate position of the DS was also
eliminated by deletion of the DS. The results confirm the DS as both a
replication origin and a place where replication forks pause. Since the
replication function of oriP is dispensable at least in
certain cell lines, the essential role of EBNA-1 for infection of these
cell lines is likely to be that of stabilizing the EBV chromosome by
associating with the 30-bp repeats of oriP. The results
also imply that in established cell lines, the EBV chromosome can be
efficiently replicated entirely from origins that are activated by
cellular factors. Presumably, initiation of replication at the DS,
mediated by EBNA-1, is important for the natural life cycle of EBV,
perhaps in establishing latent infections of normal B cells.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Initiation of DNA Replication within
oriP Is Dispensable for Stable Replication of the Latent
Epstein-Barr Virus Chromosome after Infection of Established Cell
Lines
*
Corresponding author. Mailing address for Carl L. Schildkraut: Dept. of Cell Biology (CH416), Albert Einstein College of
Medicine, 1300 Morris Park Ave., Bronx, NY 10461. Phone: (718)
430-2097. Fax: (718) 430-8574. E-mail:
schildkr{at}aecom.yu.edu. Mailing address for John L. Yates:
Department of Genetics, Roswell Park Cancer Institute, Elm and Carlton
St., Buffalo, NY 14263. Phone: (716) 845-8964. Fax: (716) 845-8449. E-mail: Yates{at}sc3101.med.buffalo.edu.
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