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

Ranid herpesvirus 1 (RaHV-1) is the etiological agent of the Lucke renal ad enocarcinoma 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 th at the genome is 217 kbp in size, a value in accordance with the most recen t published estimate (220 kbp) obtained by field-inversion gel electrophore sis. The DNA sequence of the 39,757-bp insert in 1 cosmid (cos54) was deter mined and was predicted to contain 21 complete and 3 partial genes. In all, 12 genes have distant counterparts in a fish herpesvirus (ictalurid herpes virus 1) and are present in 2 blocks, 1 of which is relatively inverted. Th is indicates that RaHV-1 belongs to the fish virus lineage of the herpesvir us family rather than to the lineage populated by mammalian and avian virus es. The remainding 12 genes in cos54 lack counterparts in any other herpesv irus. One of these encodes a putative DNA (cytosine-5) methyltransferase. T his raises the possibility that biological processes induced in the host by RaHV-1 might involve methylation of cellular DNA by the viral enzyme.