An endogenous viral element (EVE) is a DNA sequence derived from a virus, and present within the germline of a non-viral organism.
They arise when a viral DNA sequence becomes integrated into the genome of a germ cell that goes on to produce a viable organism.
Such fragments are usually not capable of producing infectious virus, but may express protein or RNA and even cell surface receptors.
Identification of orthologous EVE insertions enables the calibration of long-term evolutionary timelines for viruses, based on the estimated time since divergence of the ortholog-containing host species groups.
Remarkably, the capture of syncytin or syncytin-like genes has occurred independently, from different groups of endogenous retroviruses, in diverse mammalian lineages.
Distinct, syncytin-like genes have been identified in primates, rodents, lagomorphs, carnivores, and ungulates, with integration dates ranging from 10 to 85 million years ago.