The Evolution Of The Monkey Gene That Blocks AIDS

Editor's Choice
Main Category: HIV / AIDS
Also Included In: Genetics;  Infectious Diseases / Bacteria / Viruses
Article Date: 28 Feb 2008 - 17:00 PDT

email to a friend   printer friendly   view / write opinions   rate article

There is a gene in Asian monkeys that could have evolved as protection against lentiviruses such as HIV, according to an article written by researchers at Harvard Medical School that is published in the open-access journal PLoS Pathogens.

The well-characterized gene - TRIM5-CypA - is a hybrid of TRIM5 and CypA, two genes that already exist. The hybrid produces a single protein that can protect from viral infections such the ones closely related to HIV. This is not the first time that a TRIM5-CypA gene was found in monkeys. In 2004, researchers found a hybrid gene called TRIMCyp in South American owl monkeys.

It is standard practice among evolutionary biologists to assume that if similar DNA sequences are found in the same place in the genomes of more than one species, then the sequence evolved only once. There is a common ancestor that first has the gene, and all species that descend from the ancestor inherit it. However, this does not seem to be the history of TRIM5-CypA and TRIMCyp.

Researchers did not find the TRIM5-CypA gene in monkeys closely related to the Asian macaques, nor did they find it in every macaque monkey that was tested. Owl monkey TRIMCyp, similarly, could not be detected in any other South American primate species. The conclusion that the researchers draw about both genes is that they arose independently - one time for owl monkeys and one time for macaques. Although there are similar protein sequences specified by the two TRIM5-CypA genes, there were different molecular events at the DNA level that are responsible for the formation of each gene.

According to evolutionary biologists, different species' acquisition of a similar adaptation is called "convergent evolution." One example of this is how birds and bats independently developed flight. The Harvard team remarks that an unequivocal and striking example of convergent evolution is seen in the genetic evidence of the two TRIM5-CypA genes. Researchers believe that it is rare for these kinds of molecular events to occur that are required to construct the two TRIM5-CypA genes.

Since the hybridization process occurred at least twice during primate evolution, the combination of the TRIM5 and CypA genes has given a strong evolutionary advantage to the individuals who originally carried the gene. One theory holds that the newly formed genes protected against infection by prehistoric viruses that are similar to the modern AIDS virus. If this is true, it could mean that the modern AIDS epidemic is similar to one that may have beleaguered our primate ancestors long ago; that is, AIDS is not as unique as we have believed.

Evolution of a TRIM5-CypA Splice Isoform in Old World Monkeys
Newman RM, Hall L, Kirmaier A, Pozzi L-A, Pery E, et al.
PLoS Pathogens 4(2): e1000013. (2008).
doi:10.1371/journal.ppat.1000003
Click Here to View Journal Website

Written by: Peter M Crosta
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today