Molecular fight against viruses identified

DALLAS, April 22 (UPI) -- University of Texas scientists say they've identified the mechanism by which a protein initiates the body's immune response to viral attacks.

The Southwestern Medical Center researchers say they've determined how a form of the so-called death protein ubiquitin, which normally latches onto molecules inside cells and marks them for destruction, interacts with the protein RIG-I but doesn't mark it for destruction. Instead, that form of ubiquitin binds to and activates RIG-I, which is known to trigger the body's immune system when a virus invades a cell.

The scientists, led by Professor Zhijian Chen, reconstituted key elements of the human innate immune system in laboratory test tubes and found ubiquitin forms a unique chain-like structure that associates with RIG-I before RIG-I begins fighting viruses.

"Activation of RIG-I is the first line of our immune defenses against viral infections," said Chen. "Understanding how it comes to life is a key step in developing new approaches to antiviral therapies."

He said his team's experiments mark the first time innate immunity has been recapitulated in a test tube and the findings provide one of the missing pieces in the complex puzzle of how the body fights off infection.

The study, which included Wenwen Zeng, Ming Xu, Lijun Sun, Xiang Chen, Xiaomo Jiang, Fajian Hou and Anirban Adkikari, appears in the journal Cell.