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J Virol, April 1998, p. 3436-3441, Vol. 72, No. 4
Department of Biochemistry and Molecular
Genetics, University of Alabama at Birmingham, Birmingham, Alabama
35294-0005
Received 7 August 1997/Accepted 17 December 1997
The mechanism of DNA replication is conserved among
papillomaviruses. The virus-encoded E1 and E2 proteins collaborate to target the origin and recruit host DNA replication proteins. Expression vectors of E1 and E2 proteins support homologous and heterologous papillomaviral origin replication in transiently transfected cells. Viral proteins from different genotypes can also collaborate, albeit
with different efficiencies, indicating a certain degree of specificity
in E1-E2 interactions. We report that, in the assays of our study, the
human papillomavirus type 11 (HPV-11) E1 protein functioned with the
HPV-16 E2 protein, whereas the HPV-16 E1 protein exhibited no
detectable activity with the HPV-11 E2 protein. Taking advantage of
this distinction, we used chimeric E1 proteins to delineate the E1
protein domains responsible for this specificity. Hybrids containing
HPV-16 E1 amino-terminal residues up to residue 365 efficiently
replicated either viral origin in the presence of either E2 protein.
The reciprocal hybrids containing amino-terminal HPV-11 sequences
exhibited a high activity with HPV-16 E2 but no activity with HPV-11
E2. Reciprocal hybrid proteins with the carboxyl-terminal 44 residues
from either E1 had an intermediate property, but both collaborated more
efficiently with HPV-16 E2 than with HPV-11 E2. In contrast, chimeras
with a junction in the putative ATPase domain showed little or no
activity with either E2 protein. We conclude that the E1 protein
consists of distinct structural and functional domains, with the
carboxyl-terminal 284 residues of the HPV-16 E1 protein being the
primary determinant for E2 specificity during replication, and that
chimeric exchanges in or bordering the ATPase domain inactivate the
protein.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
The Carboxyl-Terminal Region of the Human
Papillomavirus Type 16 E1 Protein Determines E2 Protein Specificity
during DNA Replication
*
Corresponding author. Mailing address: Department of
Biochemistry and Molecular Genetics, University of Alabama at
Birmingham, 1918 University Blvd., Birmingham, AL 35294-0005. Phone:
(205) 975-8300. Fax: (205) 975-6075. E-mail: ltchow{at}uab.edu.
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