Ancient Adaptive Evolution of the Primate Antiviral DNA-Editing Enzyme
APOBEC3G
Sara L. Sawyer1 , Michael Emerman1,2 , Harmit S. Malik1

1 Division of Basic Sciences, Fred Hutchinson Cancer Research Center,
Seattle, Washington, United States of America, 2 Human Biology, Fred
Hutchinson Cancer Research Center, Seattle, Washington, United States of
America

Host genomes have adopted several strategies to curb the proliferation of
transposable elements and viruses. A recently discovered novel primate
defence against retroviral infection involves a single-stranded DNA-editing
enzyme, APOBEC3G, that causes hypermutation of HIV. The HIV-encoded virion
infectivity factor (Vif) protein targets APOBEC3G for destruction, setting
up a genetic conflict between the APOBEC3G and Vif genes. This kind of
conflict leads to rapid fixation of mutations that alter amino acids at the
protein-protein interface, referred to as positive selection. We show that
the APOBEC3G gene has been subject to strong positive selection throughout
the history of primate evolution. Unexpectedly, this selection appears more
ancient than, and is likely only partially caused by, modern lentiviruses.
Furthermore, five additional APOBEC genes in the human genome appear to be
engaged in similar genetic conflicts, displaying some of the highest signals
for positive selection in the human genome. Despite being only recently
discovered, editing of RNA and DNA may thus represent an ancient form of
host defense in primate genomes.

Read the rest at PLoS Biology
http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371%2Fjournal.pbio.0020275

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