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J. Virol. doi:10.1128/JVI.00921-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Functional Mapping of the Human Papillomavirus (HPV) Type 16 E1 Cistron

Department of Pathology, Veterans Affairs Medical Center, and The University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA

^* To whom correspondence should be addressed. Email: thomas-haugen{at}uiowa.edu.

	Abstract

Replication of the double-stranded, circular human papillomavirus (HPV) genomes requires the viral DNA replicase E1. Here we report an initial characterization of the E1 cistron of HPV-16, the most common oncogenic mucosal HPV type found in cervical and some head and neck cancers. The first step in HPV DNA replication is an initial burst of plasmid viral DNA amplification. Complementation assays between HPV-16 genomes carrying mutations in the early genes confirmed that expression of E1 was necessary for initial HPV-16 plasmid synthesis. The major early HPV-16 promoter, P97, was dispensable for E1 production in initial amplification because cis mutations inactivating P97 did not affect the trans complementation of E1^- mutants. In contrast, E1 expression was abolished by cis mutations in the splice donor site at nt 226, the splice acceptor site at nt 409 or a TATAA box at nt 7890. The mapping of 5' mRNA ends using RACE defined a promoter with a transcription start site at HPV-16 nt 14, P14. P14-initiated mRNA levels were low and required an intact TATAA (7890). E1 expression required the HPV-16 keratinocyte-dependent enhancer since cis mutations in its AP-2 and TEF-1 motifs abolished the ability of the mutant genomes to complement E1- genomes, and was further modulated by origin-proximal and distal binding sites for the viral E2 gene products. We conclude that P14-initiated E1 expression is critical for and limiting in the initial amplification of the HPV-16 genome.

This article has been cited by other articles:

• Lace, M. J., Anson, J. R., Thomas, G. S., Turek, L. P., Haugen, T. H. (2008). The E8{wedge}E2 Gene Product of Human Papillomavirus Type 16 Represses Early Transcription and Replication but Is Dispensable for Viral Plasmid Persistence in Keratinocytes. J. Virol. 82: 10841-10853 [Abstract] [Full Text]