UniProt release 15.14

Bornavirus: another viral stowaway in the human genome

Analysis of the human genome sequence has revealed that our 'book of life' is multi-authored. About 0.5% of human genes are derived from bacteria and 8% of our total genetic material results from viral infections (see also release 2.1 headline). These genomic viral "fossils" are ancient retroviruses, which are known to insert their genetic information into host chromosomal DNA. They do so by producing a DNA copy from their RNA genome by use of a viral enzyme, called reverse transcriptase. The viral DNA then integrates into the host genome, becoming a permanent part of the cell.

A recent Japanese study has unveiled another viral stowaway in the human gene pool. Several copies of the bornavirus N gene turn out to be part of the human genome and of other mammalian genomes, including chimpanzees, gorillas and African elephants. These genes are remnants of a bornavirus which presumably infected proto-hominids, and other species, some forty million years ago. This ancient virus has disappeared and nowadays bornaviruses are known to infect mainly horses, inducing neurological diseases.

This discovery came as a surprise since the bornaviral RNA genome is not known to be retrocopied into DNA at any stage of the viral replication cycle and never integrates into the host genome. This unusual integration into our ancestor's genome may have helped him survive against a pathogenic virus or may have played a role in primate evolution. As often in evolutionary biology, there are many more questions than answers, but this serves as a useful reminder that human evolution does not rely only on our own intrinsic potential, but also on a tight interaction with other living species in our environment.

A bornavirus-derived gene is actually expressed in human cells. It is called 'Endogenous Borna-like N element' (EBLN-1) and can be retrieved from UniProtKB/Swiss-Prot using the accession number Q6P2I7.

UniProtKB News

Changes concerning keywords

New keyword:

• Peters anomaly

Changes concerning the controlled vocabulary for PTMs

Modified terms for the feature key 'Modified residue' ('MOD_RES' in the flat file):

New terms:

• Diiodotyrosine
• Glycyl adenylate
• Iodotyrosine
• Threonine methyl ester

Modified term for the feature key 'Cross-link' ('CROSSLNK' in the flat file):

New term:

• Glycyl cysteine dithioester (Gly-Cys) (interchain with C-...)