Endogenous retroviruses (ERVs) are genomic loci that are derived from the ancestral insertion of an exogenous retrovirus into the host genome. ERV loci are generally out of scope for RefSeq; however, we annotate full-length ERV protein-coding loci that map to a single genomic location if they have evolved to serve a host function, are associated with a known disease, and/or if they have been assigned nomenclature by an official nomenclature committee. About 8% of the human genome is of retroviral origin (27); however due to their ancient origins most human ERV loci have accumulated nonsense mutations and can no longer encode a protein. The syncytin proteins, which are involved in placental development (28), are a well-known exception to this. Human syncytin-1 and syncytin-2 proteins are encoded by the ERVW-1 (NM_001130925.1, NM_014590.3) and ERVFRD-1 (NM_207582.2) genes. To date we have created 67 RefSeqs for ERV loci, which includes records representing ERV genes from a diverse set of mammals. A new RefSeq attribute category entitled ‘endogenous retrovirus’ was created for these records and appears in a structured comment on the RefSeq record. These records can be retrieved from the Nucleotide database by searching for ‘endogenous retrovirus [properties]’.
