FELINE IMMUNODEFICIENCY VIRUS GENE-EXPRESSION - ANALYSIS OF THE RNA SPLICING PATTERN AND THE MONOCISTRONIC REV MESSENGER-RNA

The transcription pattern of the feline immunodeficiency virus (FIV) g enome in a feline CD4+ cell line was examined. In addition to the geno mic RNA (9.2 kb), at least five FIV-specific transcripts [5-2, 4.4 (do ublet), 1-7 and 1.4 kb] were detected by using subgenomic restriction enzyme fragments of an FIV molecular clone or FIV-specific oligonucleo tides as probes. Among these transcripts, the 9.2, 5.2 and 4.4 (double t) kb mRNAs were not expressed in the cytoplasm of cells transfected w ith a rev- mutant. To determine the location of splice junctions in th e FIV genome, we used PCR to amplify and clone cDNAs corresponding to the viral mRNAs from infected cells. The region between pol and env wa s found to contain at least two splice donor and three splice acceptor sites. Two splice acceptor sites were detected in the 3' region of en v. By hybridization analysis and sequencing of cDNA clones, it was rev ealed that the medium sized mRNAs are derived from a single splice eve nt, with different splice acceptor sites, and that the two smaller tra nscripts are doubly or triply spliced mRNAs. Our results demonstrate a complex pattern of alternative splicing of FIV mRNAs. Furthermore, we identified monocistronic rev mRNA species that employ a unique splice acceptor site.