Journal of Virology, June 2000, p. 4939-4948, Vol. 74, No. 11
Department of Biochemistry, McMaster
University, Hamilton, Ontario L8N 3Z5,1 and
Department of Medical Genetics and Microbiology, University of
Toronto, Toronto, Ontario M5S 1A8,2 Canada
Received 8 November 1999/Accepted 3 March 2000
The EBNA1 protein of Epstein-Barr virus (EBV) governs the
replication and segregation of the viral episomes in latently infected cells and transactivates the expression of other EBV latency proteins through direct interactions with DNA sequences in the EBV latent origin
of replication, oriP. To better understand how EBNA1
controls these processes, we have assessed the contribution of various EBNA1 sequences to its replication, segregation, and transactivation functions. Here we show that EBNA1 residues 325 to 376 are responsible for the transactivation activity of EBNA1. This region coincides with
the DNA looping domain previously shown to mediate interactions at a
distance between DNA-bound EBNA1 molecules. The same residues mediate
DNA segregation but have no apparent role in DNA replication, indicating that the replication and transcription activation activities of EBNA1 are distinct. The acidic C-terminal tail of EBNA1 was not
found to contribute to replication, transactivation, or segregation. We
have also investigated the functional significance of two structural motifs within the DNA binding and dimerization domains of EBNA1, the
proline loop and the WF motif. Although the amino acids in these motifs
do not directly contact the DNA, both of these motifs were found to
contribute to EBNA1 functions by increasing the DNA-binding ability of
EBNA1. Mechanisms by which DNA binding is stimulated by these motifs
are discussed.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Functional Analyses of the EBNA1 Origin DNA Binding
Protein of Epstein-Barr Virus
*
Corresponding author. Mailing address: Department of
Medical Genetics and Microbiology, University of Toronto, 1 Kings
College Circle, Toronto, Ontario M5S 1A8, Canada. Phone: (416)
946-3501. Fax: (416) 978-6885. E-mail:
lori.frappier{at}utoronto.ca.
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