Bornavirus enters the genome

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Abstract
A survey of mammalian genomes has unexpectedly unearthed DNA derived from bornaviruses, leading to speculation about the role of these viruses in causing mutations with evolutionary and medical consequences. DNA derived from endogenous retroviruses is a common ancestral feature in mammalian genomes. Until now retroviruses have been the only group of viruses known to have left a fossil record of this type, but now elements derived from Borna-like N (EBLN) sequences have been found in the genomes of humans, non-human primates, rodents and a species of ground squirrel. Bornaviruses are non-segmented, negative-strand RNA viruses that replicate in the nucleus of infected cells. In primates, the elements are very old, formed more than 40 million years ago, while squirrel EBLN sequences are a more recent introduction. The conservation of open reading frames of primate EBLNs, as well as their expression as mRNA, implies that they may function as a source of genetic novelty in their host.