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Journal of Virology, June 2005, p. 7014-7023, Vol. 79, No. 11
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.11.7014-7023.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Leiping Fu,1
Rolando Herrero,3
Rob DeSalle,4 and
Robert D. Burk1,2*
Department of Microbiology & Immunology,1 Departments of Pediatrics, Epidemiology & Population Health, and Obstetrics, Gynecology and Women's Health, Albert Einstein Cancer Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461,2 Proyecto Epidemiológico Guanacaste, Costa Rican Foundation for Health Sciences, San José, Costa Rica,3 Division of Invertebrate Zoology, American Museum of Natural History, New York, New York 100244
Received 18 October 2004/ Accepted 27 January 2005
Human
papillomavirus type 16 (HPV16) is the primary etiological
agent of cervical cancer, the second most common cancer in women
worldwide. Complete genomes of 12 isolates representing the major
lineages of HPV16 were cloned and sequenced from cervicovaginal cells.
The sequence variations within the open reading frames (ORFs) and
noncoding regions were identified and compared with the HPV16R
reference sequence (50).
This whole-genome approach gives us unprecedented precision in
detailing sequence-level changes that are under selection on a
whole-viral-genome scale. Of 7,908 base pair nucleotide positions, 313
(4.0%) were variable. Within the 2,452 amino acids
(aa) comprising 8 ORFs, 243 (9.9%) amino acid positions were
variable. In order to investigate the molecular evolution of HPV16
variants, maximum likelihood models of codon substitution were
used to identify lineages and amino acid sites under selective
pressure. Five codon sites in the E5 (aa 48, 65) and E6 (aa
10, 14, 83) ORFs were demonstrated to be under diversifying selective
pressure. The E5 ORF had the overall highest nonsynonymous/synonymous
substitution rate (
) ratio (M3 = 0.7965). The E2 gene
had the next-highest
ratio (M3 = 0.5611); however, no
specific codons were under positive selection. These data
indicate that the E6 and E5 ORFs are evolving under positive Darwinian
selection and have done so in a relatively short time period. Whether
response to selective pressure upon the E5 and E6 ORFs
contributes to the biological success of HPV16, its specific biological
niche, and/or its oncogenic potential remains to be
established.
Present address: National Research Institute for Child Health & Development, 3-35-31 Taishidoh, Setagaya, Tokyo 154-8567, Japan.
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