An RNA-dependent RNA polymerase gene in bat genomes derived from an ancient negative-strand RNA virus

Horie, Masayuki; Kobayashi, Yuki; Honda, Tomoyuki; Fujino, Kan; Akasaka, Takumi; Kohl, Claudia; Wibbelt, Gudrun; Mühldorfer, Kristin; Kurth, Andreas; Müller, Marcel A.; Corman, Victor M.; Gillich, Nadine; Suzuki, Yoshiyuki; Schwemmle, Martin; Tomonaga, Keizo

Endogenous bornavirus-like L (EBLL) elements are inheritable sequences derived from ancient bornavirus L genes that encode a viral RNA-dependent RNA polymerase (RdRp) in many eukaryotic genomes. Here, we demonstrate that bats of the genus Eptesicus have preserved for more than 11.8 million years an EBLL element named eEBLL-1, which has an intact open reading frame of 1,718 codons. The eEBLL-1 coding sequence revealed that functional motifs essential for mononegaviral RdRp activity are well conserved in the EBLL-1 genes. Genetic analyses showed that natural selection operated on eEBLL-1 during the evolution of Eptesicus. Notably, we detected efficient transcription of eEBLL-1 in tissues from Eptesicus bats. To the best of our knowledge, this study is the first report showing that the eukaryotic genome has gained a riboviral polymerase gene from an ancient virus that has the potential to encode a functional RdRp.