Enzyme able to block HIV replication in human body

October 13th, 2008 - 5:21 pm ICT by IANS  

Washington, Oct 13 (IANS) An enzyme present in every human cell is capable of stopping HIV at the first step of replication, when the retrovirus transcribes its RNA into viral DNA.The study’s authors, led by Xiaojiang Chen of the University of Southern California (USC), were able to map the atomic structure of the active portion of enzyme APOBEC-3G. The discovery suggests how and where the enzyme binds to the viral DNA, mutating and destroying it.

“We understand how this enzyme can interact with DNA,” said Chen, a professor of molecular and computational biology at USC. “This understanding provides a platform for designing anti-HIV drugs.”

If APOBEC-3G works so well, why do people get AIDS? Because the HIV virus has evolved to encode the protein Vif, known as a “virulence factor,” that blocks APOBEC-3G, according to an USC release.

With APOBEC-3G out of the way, the RNA of the HIV virus can be successfully transcribed to viral DNA, an essential step for infection and for producing many more HIV viruses.

Chen said his group’s research offers important clues on where Vif binds to APOBEC-3G. The knowledge could be used to design drugs that would prevent Vif from binding and allow APOBEC-3G to do its job, Chen said.

That would unlock humans’ innate ability to fight HIV. “We were born with it, and it’s there waiting,” Chen said. In addition to fighting HIV, APOBEC-3G can inhibit the Hepatitis B virus. Other members of the APOBEC family serve important roles in antibody maturation, fat metabolism and heart development.

Mapping the structure of APOBEC-3G at the atomic level is a goal that “has been sought after worldwide because of its significance,” Chen said.

The study was published online in Nature.

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