Genomic studies of the Lucké tumor herpesvirus (RaHV-1)

Abstract

Ranid herpesvirus 1 (RaHV-1) is the etiological agent of the Lucké renal adenocarcinoma of the North American leopard frog Rana pipiens. Construction of cosmid libraries containing RaHV-1 DNA inserts allowed the derivation of a BamHI map for the viral genome. Summation of fragment sizes indicates that the genome is 217 kbp in size, a value in accordance with the most recent published estimate (220 kbp) obtained by field-inversion gel electrophoresis. The DNA sequence of the 39,757-bp insert in 1 cosmid (cos54) was determined and was predicted to contain 21 complete and 3 partial genes. In all, 12 genes have distant counterparts in a fish herpesvirus (ictalurid herpesvirus 1) and are present in 2 blocks, 1 of which is relatively inverted. This indicates that RaHV-1 belongs to the fish virus lineage of the herpesvirus family rather than to the lineage populated by mammalian and avian viruses. The remaining 12 genes in cos54 lack counterparts in any other herpesvirus. One of these encodes a putative DNA (cytosine-5) methyltransferase. This raises the possibility that biological processes induced in the host by RaHV-1 might involve methylation of cellular DNA by the viral enzyme.

Toward a Comprehensive Phylogeny for Mammalian and Avian Herpesviruses

“…Phylogenetic studies using herpesvirus sequences have been undertaken, demonstrating clear division into the three subfamilies and, in some sublineages, patterns of divergence consistent with cospeciation of virus and host (7,9,13,14). Herpesviruses of fish (2,3), amphibians (4), and invertebrates (A. J. Davison, personal communication) are only remotely related to the mammalian and avian viruses, while certain turtle viruses (the only reptile herpesviruses for which some sequence is known) probably group with the mammalian and avian viruses (18).…”

Herpesviruses of Fish, Amphibians and Invertebrates

“…Herpesviruses are large and complex DNA viruses with a distinctive virion morphology, which consists of four distinct structures: the core, capsid, tegument, and envelope (Davison et al, 2005a). The order Herpesvirales is subdivided into three families , which separated about 500 million years ago (McGeoch et al, 2006).…”

“…Herpesviruses are large and complex DNA viruses which infect a wide range of vertebrates and invertebrates, including humans and domestic animals (Davison et al, 2005a). Severe infections are usually only observed in foetuses and very young or immunocompromised individuals, but economic consequences for livestock can be significant.…”

Host epigenetic modifications by oncogenic viruses

“…Interestingly, ranid herpesvirus 1 (RaHV-1), which is the aeitiological agent of kidney cancers in the North American leopard frog Rana pipiens encodes its own DNA (cytosine-5) methyltransferase, further suggesting that alteration of methylation in the host genome is a highly conserved function in oncogenic viruses (Davison et al, 1999). Again, in nonviral cancers, this is also a common finding with an overall increase in DNA methyltransferase activity in many tumours compared with normal tissues (Esteller, 2006).…”