Viruses have long been speculated to be a source of novel animal genes, yet little evidence, except from retroviruses, has supported this idea. The team's motivation included the desire to search for such evidence in other viruses.
"We first scanned all published vertebrate genomes for traces of single stranded RNA (ssRNA) viruses other than retroviruses," says Skalka. The team then used a variety of techniques to devise a new method for determining the age of DNA sequences. "To our amazement, we discovered ancient fossils [viral sequences] in 19 vertebrate species that are related to certain currently circulating RNA viruses," notably the deadly Ebolaviruses, and the Bornaviruses, she says. These results, published earlier this year, encouraged these investigators to look for ancient fossils derived from ssDNA viruses.
"Once again we were amazed to find sequences from replication (rep) and capsid genes from ancient viruses related to the Parvovirus and Circovirus families in 31 of the 49 vertebrate genomes we tested," says Skalka.
While rep proteins from the circoviruses were already knownsome of them selectively kill tumor cellsthe relevant codes were certainly not known to have existed in vertebrates almost as far back as when the dinosaurs roamed earth. Skalka notes that there is no evidence yet that those coding sequences are expressed. "But should a beneficial role for these integrations be found, such as control of cancer progression, it may explain why these viruses were selected for over millions of years of vertebrate evolution."
One additional notable finding is that the timeframe of the viral fossils' appearan
|Contact: Jim Sliwa|
American Society for Microbiology