TRANSCRIPTIONAL ANALYSIS OF WALLEYE DERMAL SARCOMA-VIRUS (WDSV)

Walleye dermal sarcoma virus (WDSV) is a complex retrovirus associated with dermal sarcomas of walleye that develop and regress on a seasona l basis. WDSV contains, in addition to gag, pol, and env, three open r eading frames (ORFs) designated ORF A, ORF B, and ORF C. The polymeras e chain reaction technique was used to amplify and clone cDNAs represe nting subgenomic viral mRNAs isolated from developing (fall) and regre ssing (spring) tumors. Nine different singly or multiply spliced viral transcripts were identified and all were found to utilize a common 5' leader sequence. This leader sequence is spliced to the pol/env junct ion or downstream of env to generate singly spliced transcripts. Multi ply spliced transcripts contain the 5' leader, the pol/env junction, a nd sequences derived from the 3' end of the genome. One multiply splic ed transcript was isolated with the potential to encode the full-lengt h ORF A protein. In addition, WDSV produced mRNAs that utilize alterna tive splice acceptor sites which would allow synthesis of five variant forms of the ORF A protein. In contrast, the ORF B protein is postula ted to arise from a singly spliced transcript with the potential to en code the entire open reading frame. Spliced subgenomic transcripts rep resenting ORF C mRNAs were not identified, suggesting that ORF C may b e encoded from the full-length viral genomic transcript, We estimate t hat at least a 100-fold lower amount of the accessory/regulatory subge nomic transcripts exists in developing vs regressing tumors. These res ults demonstrate that WDSV undergoes an elaborate pattern of mRNA spli cing similar to that of other complex retroviruses. (C) 1997 Academic Press.