[Genome virology: the novel interaction of RNA viruses and host genomes]

The origin of virus-like organisms probably dates back to the earliest forms of cellular life. Such a long coexistence between viruses and ourselves suggests that viruses may have crucially influenced the evolution of our species and vice versa. Sequences derived from retroviruses and retrotransposons have been shown to make up a substantial part of the human genome, suggesting a direct role of virus infection as a source of new genetic information and genomic innovation of the host species. Until very recently, retroviruses were the only viruses known to generate such endogenous copies in vertebrate genomes. However, we and others have reported recently that non-retroviral RNA viruses, including bornaviruses and filoviruses, have been endogenized repeatedly during mammalian evolution. These endogenous elements of RNA viruses not only provide evidence of ancient viral infections in each animal species but also offer novel paradigms for the interaction between RNA viruses and their hosts. Based on the presentation of the plenary lecture at the XV International Congress of Virology 2011, I will review here our recent findings regarding the generation and functions of endogenous bornavirus-like N elements in mammalian genomes, in order to reveal the unknown dynamics of RNA viruses in eukaryotic cells, and also discuss the evolutionary interaction between RNA viruses and hosts.