Genetic analysis of the feline RD-114 retrovirus-related endogenous elements

The structure of the multiple copies of the endogenous RD-114 retroviral sequences in the domestic cat were compared by restriction mapping of cloned and genomic DNAs. Six different clones, each representing a different loci, were randomly chosen from 20 clones isolated from a cat DNA library. Whereas all clones contained viral structural sequences which were extensively homologous to the gag and pol regions of exogenous RD-114, they varied from each other in the extent of deletions (0.7-1.9 kilobase pairs) in the env region. Each clone contained a pair of LTRs which bracketed the structural genes, implicating an origin from exogenous infection of a distant ancestor of the domestic cat. Analysis of genomic DNA from six separate domestic cats also indicated that the majority of the RD-114 endogenous loci contained variably deleted env and conserved gag-pol regions. The occurrence of at least 13 unique RD-114-related loci could be detected in each cat DNA examined. It appeared that among these multiple copies inherited in the cat genome, there is only a single copy which would correspond to the undeleted RD-114 provirus, and which may represent the locus for the inducible RD-114 virus.