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Journal of Virology, November 1999, p. 9393-9403, Vol. 73, No. 11
Department of Microbiology and Immunology,
College of Veterinary Medicine, Cornell University, Ithaca, New
York 14853
Received 16 April 1999/Accepted 30 July 1999
Walleye epidermal hyperplasia virus types 1 and 2 (WEHV1 and WEHV2,
respectively) are associated with a hyperproliferative skin lesion on
walleyes that appears and regresses seasonally. We have determined the
complete nucleotide sequences and transcriptional profiles of these
viruses. WEHV1 and WEHV2 are large, complex retroviruses of 12,999 and
13,125 kb in length, respectively, that are closely related to one
another and to walleye dermal sarcoma virus (WDSV). These walleye
retroviruses contain three open reading frames, orfA,
orfB, and orfC, in addition to
gag, pol, and env. orfA and
orfB are adjacent to one another and located downstream of env. The OrfA proteins were previously
identified as cyclin D homologs that may contribute to the induction of
cell proliferation leading to epidermal hyperplasia and dermal sarcoma. The sequence analysis of WEHV1 and WEHV2 revealed that the OrfB proteins are distantly related to the OrfA proteins, suggesting that
orfB arose by gene duplication. Presuming that the
precursor of orfA and orfB was derived from a
cellular cyclin, these genes are the first accessory genes of complex
retroviruses that can be traced to a cellular origin. WEHV1, WEHV2, and
WDSV are the only retroviruses that have an open reading frame,
orfC, of considerable size (ca. 130 amino acids) in the
leader region preceding gag. While we were unable to
predict a function for the OrfC proteins, they are more conserved than
OrfA and OrfB, suggesting that they may be biologically important to
the viruses. The transcriptional profiles of WEHV1 and WEHV2 were also
similar to that of WDSV; Northern blot analyses detected only low
levels of the orfA transcripts in developing lesions,
whereas abundant levels of genomic, env, orfA,
and orfB transcripts were detected in regressing lesions. The splice donors and acceptors of individual transcripts were identified by reverse transcriptase PCR. The similarities of WEHV1, WEHV2, and WDSV suggest that these viruses use similar strategies of
viral replication and induce cell proliferation by a similar mechanism.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Sequence and Transcriptional Analyses of the Fish
Retroviruses Walleye Epidermal Hyperplasia Virus Types 1 and 2:
Evidence for a Gene Duplication


*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401. Phone: (607) 253-3579. Fax: (607)
253-3384. E-mail: jwc3{at}cornell.edu.
Present address: Department of Biomedical Sciences, College of
Osteopathic Medicine, Ohio University, Athens, OH 45701.
Present address: Department of Biological Sciences, Ohio
University, Athens, OH 45701.
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