MicrobiologyBytes

It was my priveledge to work with Brian Mahy many years ago. Brian has just retired as long-serving Editor of Virus Research, and his swansong is an excellent special issue on negative strand RNA viruses – an important read for all virologists and an even more impirtant one for all aspiring virologists.

Virus Research: Negative Strand RNA Viruses Special Issue

• Insights on influenza pathogenesis from the grave
• Taming influenza viruses
• Induction and evasion of type I interferon responses by influenza viruses
• Immune responses to influenza virus infection
• Novel vaccines against influenza viruses
• Prospects for controlling future pandemics of influenza
• New concepts in measles virus replication: Getting in and out in vivo and modulating the host cell environment
• Recombinant vaccines against the mononegaviruses—What we have learned from animal disease controls
• Biological feasibility of measles eradication
• Progress in understanding and controlling respiratory syncytial virus: Still crazy after all these years
• An unconventional pathway of mRNA cap formation by vesiculoviruses
• Rhabdovirus accessory genes
• Structural insights into the rhabdovirus transcription/replication complex
• Hantavirus pulmonary syndrome
• Progress in recombinant DNA-derived vaccines for Lassa virus and filoviruses
• Borna disease virus – Fact and fantasy
• A review of Nipah and Hendra viruses with an historical aside
• Negative-strand RNA viruses: The plant-infecting counterparts
• Quasispecies as a matter of fact: Viruses and beyond

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Even before I wrote my online notes about Bornaviruses over 10 years ago, this group of viruses was always a bit of a mystery. Considerable controversy still surrounds the role of these viruses in human pathogenesis, so it is of great interest that a report has just been published in Nature describing how Bornavirus-like sequences have been repeatedly incorporated into the genome during mammalian evolution. BDV infection might create a source of mutation in infected individuals, which allows a testable hypothesis for the alleged, but still controversial, causative association of BDV infection with certain psychiatric disorders, such as schizophrenia and mood disorders.

Endogenous non-retroviral RNA virus elements in mammalian genomes. Nature 463, 84, (2010). doi:10.1038/nature08695
Retroviruses are the only group of viruses known to have left a fossil record, in the form of endogenous proviruses, and approximately 8% of the human genome is made up of these elements. Although many other viruses, including non-retroviral RNA viruses, are known to generate DNA forms of their own genomes during replication, none has been found as DNA in the germline of animals. Bornaviruses, a genus of non-segmented, negative-sense RNA virus, are unique among RNA viruses in that they establish persistent infection in the cell nucleus. Here we show that elements homologous to the nucleoprotein (N) gene of bornavirus exist in the genomes of several mammalian species, including humans, non-human primates, rodents and elephants. These sequences have been designated endogenous Borna-like N (EBLN) elements. Some of the primate EBLNs contain an intact open reading frame (ORF) and are expressed as mRNA. Phylogenetic analyses showed that EBLNs seem to have been generated by different insertional events in each specific animal family. Furthermore, the EBLN of a ground squirrel was formed by a recent integration event, whereas those in primates must have been formed more than 40 million years ago. We also show that the N mRNA of a current mammalian bornavirus, Borna disease virus (BDV), can form EBLN-like elements in the genomes of persistently infected cultured cells. Our results provide the first evidence for endogenization of non-retroviral virus-derived elements in mammalian genomes and give novel insights not only into generation of endogenous elements, but also into a role of bornavirus as a source of genetic novelty in its host.

Related:

• MicrobiologyBytes: Bornaviruses
• Infectobesity: the bugs that make you fat
• News and Views (subscription): Bornavirus enters the genome