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Journal of Virology, July 1999, p. 5282-5293, Vol. 73, No. 7
Department of Biological Sciences,
Bio-Méga Research Division, Boehringer Ingelheim (Canada)
Ltd., Laval, Canada H7S 2G5
Received 21 December 1998/Accepted 29 March 1999
Replication of the genome of human papillomaviruses (HPV) is
initiated by the recruitment of the viral E1 helicase to the origin of
DNA replication by the viral E2 protein, which binds specifically to
the origin. We determined, for HPV type 11 (HPV-11), that the
C-terminal 296 amino acids of E1 are sufficient for interaction with
the transactivation domain of E2 in the yeast two-hybrid system and in
vitro. This region of E1 encompasses the ATP-binding domain. Here we
have examined the role of this ATP-binding domain, and of ATP, on
E2-dependent binding of E1 to the origin. Several amino acid
substitutions in the phosphate-binding loop (P loop), which is
implicated in binding the triphosphate moiety of ATP, abolished E2
binding, indicating that the structural integrity of this domain is
essential for the interaction. The structural constraints imposed on
the E1 P loop may differ between HPV-11 and bovine papillomavirus type
1 (BPV-1), since the P479S substitution that inactivates BPV-1 E1 is
tolerated in the HPV-11 enzyme. Other substitutions in the E1 P loop,
or in two other conserved motifs of the ATP-binding domain, were
tolerated, indicating that ATP binding is not essential for interaction
with E2. Nevertheless, ATP-Mg stimulated the E2-dependent binding of E1
to the origin in vitro. This stimulation was maximal at the
physiological temperature (37°C) and did not require ATP hydrolysis.
In contrast, ATP-Mg did not stimulate the E2-dependent binding to the
origin of an E1 protein containing only the C-terminal domain (353 to
649) or that of mutant E1 proteins with alterations in the DNA-binding domain. These results are discussed in light of a model in which the E1
ATP-binding domain is required for formation of the E2-binding surface
and can, upon the binding of ATP, facilitate and/or stabilize the
interaction of E1 with the origin.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Role of the ATP-Binding Domain of the Human
Papillomavirus Type 11 E1 Helicase in E2-Dependent Binding to the
Origin
*
Corresponding author. Mailing address: Department of
Biological Sciences, Bio-Méga Research Division, Boehringer
Ingelheim (Canada) Ltd., 2100 Cunard St., Laval, Canada H7S 2G5. Phone: (450) 682-4640. Fax: (450) 682-8434. E-mail:
jarchambault{at}lav.boehringer-ingelheim.com.
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