"Jumping genes" essentially cut themselves out of the genetic material, and scientists have suspected that this ability might have been borrowed by cells needing to build many different proteins from a specific, single set of instructions -- the key to recognizing a million immune-stimulating proteins. But until now, no jumping gene was known to behave just right.

Writing in the Dec. 23 issue of Nature, the researchers show that a jumping gene called Hermes, still active in the common house fly, creates changes in DNA very much like those created by the process behind antigen recognition.

"Hermes behaves more like the process used by the immune system to recognize a million different proteins, called antigens, than any previously studied jumping gene," says Nancy Craig, Ph.D., professor of molecular biology and genetics in Johns Hopkins' Institute for Basic Biomedical Sciences and a Howard Hughes Medical Institute investigator. "It provides the first real evidence that the genetic processes behind antigen diversity might have evolved from the activity of a jumping gene, likely a close relative of Hermes."

Recognition of so many antigens allows the immune system to fight infection and distinguish friend from foe. The "big picture" behind this ability is that cells build proteins called antibodies that bind to particular antigens, but the early steps of that process have been difficult to study. Hermes should help reveal some secrets of this process, the researchers say.

"The immune system takes an approach to protein building similar to that of diners creating a meal at a cafeteria, but how the immune system's 'a
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Contact: Joanna Downer
jdowner1@jhmi.edu
410-614-5105
Johns Hopkins Medical Institutions
22-Dec-2004