Eight Percent of Human Genetic Material Comes from a Virus

http://www.sciencedaily.com/releases/2010/01/100107103621.htm

ScienceDaily (Jan. 8, 2010) — About eight percent of human genetic material comes from a virus and not from our ancestors, according to researchers in Japan and the U.S.

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The research showed that the genomes of humans and other mammals contain DNA derived from the insertion of bornaviruses, RNA viruses whose replication and transcription takes place in the nucleus. Feschotte wrote on recent research led by Professor Keizo Tomonaga at Osaka University in Japan. Feschotte said this virally transmitted DNA may be a cause of mutation and psychiatric disorders such as schizophrenia and mood disorders.

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The assimilation of viral sequences into the host genome is a process referred to as endogenization. This occurs when viral DNA integrates into a chromosome of reproductive cells and is subsequently passed from parent to offspring. Until now, retroviruses were the only viruses known to generate such endogenous copies in vertebrates. But Feschotte said that scientists have found that non-retroviral viruses called bornaviruses have been endogenized repeatedly in mammals throughout evolution.

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