The biological significance of bornavirus-derived genes in mammals

•Various mammals harbor bornavirus-derived sequences in their genomes.•Some products from bornavirus-derived genes could suppress bornavirus replication.•A bornavirus-derived protein is involved in cellular functions in human cells.•Extensive surveys of bornaviruses are required for studies of bornavirus-derived genes.

The discoveries of sequences derived from non-retroviral viruses in eukaryotic genomes have significantly expanded our knowledge about virus evolution as well as the co-evolution between viruses and eukaryotes. However, the biological functions of such sequences in the host are largely unknown. Endogenous bornavirus-like elements (EBLs) have been relatively well studied by molecular biological methods, which have provided evidence that some EBLs have been co-opted by their hosts. This review highlights the current knowledge on the biological significance of EBLs, and discusses possible functions of EBLs. Further, we highlight the importance of extensive surveillance of exogenous viruses for a better understanding of endogenous viral sequences as well as the co-evolution of viruses and eukaryotes.