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J Virol, July 1998, p. 5735-5744, Vol. 72, No. 7
Department of Biochemistry and Kaplan
Comprehensive Cancer Center, New York University Medical Center,
New York, New York 10016
Received 4 December 1997/Accepted 31 March 1998
The modulation of DNA replication by transcription factors was
examined by using bovine papillomavirus type 1 (BPV). BPV replication in vivo requires two viral proteins: E1, an origin-binding protein, and
E2, a transcriptional transactivator. In the origin, E1 interacts with
a central region flanked by two binding sites for E2 (BS11 and BS12),
of which only BS12 has been reported to be essential for replication in
vivo. Using chemical interference and electrophoretic mobility shift
assays, we found that the binding of E2 to each site stimulates the
formation of distinct E1-origin complexes. A high-mobility C1 complex
is formed by using critical E2 contacts to BS12 and E1 contacts to the
dyad symmetry element. In contrast, interaction of E2 with the BS11
element on the other origin flank promotes the formation of the
lower-mobility C3 complex. C3 is a novel species that resembles C2, a
previously identified complex that is replication active and formed by
E1 alone. The binding of E1 greatly differs in the C1 and C3 complexes,
with E1 in the C1 complex limited to the origin dyad symmetry region
and E1 in the C3 complex encompassing the region from the proximal edge of BS11 through the distal edge of BS12. We found that the presence of
both E2-binding sites is necessary for wild-type replication activity
in vivo, as well as for maximal production of the C3 complex. These
results show that in the normal viral context, BS11 and BS12 play
separate but synergetic roles in the initiation of viral DNA
replication that are dependent on their location within the origin. Our
data suggest a model in which the binding of E2 to each site
sequentially stimulates the formation of distinct E1-origin complexes,
leading to the replication-competent complex.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Distinct Roles of Two Binding Sites for the Bovine
Papillomavirus (BPV) E2 Transactivator on BPV DNA Replication
and
*
Corresponding author. Mailing address: Department of
Biochemistry and Kaplan Comprehensive Cancer Center, New York
University Medical Center, 550 First Ave., New York, NY 10016. Phone:
(212) 263-8453. Fax: (212) 263-8166. E-mail:
borowj01{at}mcrcr.med.nyu.edu.
Present address: Department of Pathology, University of Texas
Southwestern Medical Center, Dallas, TX 75235.
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