LAUSR

Significance Endogenous retroviruses (ERVs) are remnants of ancestral viral infections of cells and occupy substantial proportions of mammalian genomes. Most ERVs have numerous mutations, deletions, and insertions in the coding region; truncated envelope (env) genes are scattered throughout the genomes. The truncated Envelope (Env) proteins consist of a signal peptide and the N-terminal region of the surface unit, but they lack a transmembrane domain; these proteins are secreted from cells in soluble form and block viral infection via competition with entry receptors. This defense system could function to prevent both intraspecies and interspecies transmission of viral infections. Truncated Envs have been independently acquired by infection with ancient viruses, and they could prevent the spread of infectious diseases.