Repetitive DNA insertion in a protein kinase ORF of a latent FSV (Feldmannia sp. virus) genome

We describe the structure of a Feldmannia sp. virus (FsV) genome integrated in the brown alga, Feldmannia. This integrated FsV genome appears to be permanently inactivated and lost its ability to excise and replicate. Unlike the replicated form of FsV, this integrated FsV genome contains a large (>50 kb) repeat region inserted in a protein kinase open reading frame. While related to the 173-bp repeats previously characterized in the FsV genome (Lee et al., 1995), Southern blot analysis indicates that the repeats in the inactive, integrated FsV genome are distinct from those previously characterized. Fine structural analysis of the repeat-insertion sites in the protein kinase gene indicates that there are 8- and 10-bp palindromic sequences present in multiple locations located near the repeat-insertion site. The translated protein kinase contains all of the catalytic motifs conserved in most serine/threonine protein kinases and a potential autophosphorylation site. This protein kinase gene is expressed as RNA in sporophyte plants where virus production is active but not in gametophyte plants where the virus genome is latent. The structure of the integrated virus genome is discussed.