The Plastic Genome

The poxvirus stockpiles genes when it needs to adapt.

Beth Marie Mole
Dec 1, 2012


THE VIRAL ACCORDION: In times of stress, vaccinia viruses (blue) expand their DNA (green) by making duplicate copies of beneficial genes.© SPL/SCIENCE SOURCE

The paper
N.C. Elde et al., “Poxviruses deploy genomic accordions to adapt rapidly against host antiviral defenses,” Cell, 150:831-41, 2012.

The finding
Double-stranded DNA viruses, such as poxviruses, were thought to mutate slowly despite keeping pace with rapidly shifting host defenses. Now, Harmit Malik at the Fred Hutchinson Cancer Research Center and colleagues have found that poxviruses expand their genome—making duplicate copies of genes—which allows more beneficial mutations to arise and hastens adaptive viral offensives.

The war zone
Nels Elde, at the time a postdoc in Malik’s lab, grew vaccinia virus in unfavorable conditions, namely in human cells that produced a viral inhibitor named protein kinase R (PKR). Although vaccinia virus carries a gene for one version of a PKR antagonist...