Nongene DNA boosts AIDS risk

From San Diego, at a meeting of the American Society of Human Genetics

A newly discovered genetic variation raises some people’s vulnerability to infection by HIV, the virus that causes AIDS.

People who have this difference in a single letter of their genetic code would have about a 15 percent greater risk that exposure to the virus will lead to infection than would individuals without the genetic variation. That conclusion comes from laboratory studies of human cells by Samuel Deutsch of the University of Geneva and his colleagues there and at the University of Lausanne in Switzerland.

Once infected, furthermore, those with the variation fare worse than other HIV-positive people. In a comparison of 805 HIV patients not yet receiving antiviral drugs, the 56 people with the mutation showed a more rapid decline of the immune system than did those without the mutation.

Yet this variation occurs in a region of DNA far from any protein-encoding genes, in an area of so-called junk DNA that scientists once presumed to have no function.

“This is in the middle of nowhere,” Deutsch says. The discovery is another example of scientists finding that some DNA formerly considered junk actually regulates the activity of genes. Because of this regulatory role, mutations in these regions can influence cell behavior and sometimes contribute to disease (SN: 9/8/07, p. 154).

The HIV-related mutation appears to regulate a cluster of about six genes with unknown functions, though further research is needed to confirm this, Deutsch says.

Whatever the regulated genes turn out to be, the proteins they produce are likely to be part of the mechanism by which HIV infects human cells. The proteins would therefore provide targets for developing drugs that combat infection.

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