The scientists, who included Albert Jeltsch of Jacobs University in Breman, Germany; Yoichi Shinkai at Japan's Kyoto University; and Professor Xiaodong Cheng at Emory University explained histones are the group of proteins that creates tightly bundled packages of DNA strands.

The modification enzymes, called protein methyltransferases, add methyl groups to lysine amino acids within the histones and change their influence on gene expression. The researchers found a histone methyltransferase called G9a adds methyl groups to other proteins in addition to histones and changes the behavior of those proteins.

"This discovery broadens our view of methyltransferases and tells us that epigenetic regulation in cells is even more complicated than we thought," said Cheng, the principal investigator. "We have known for some time that we had a great deal more to discover about methyltransferases.

"This is an important piece of the puzzle and additional research will continue to help us unwind the multiple mechanisms involved in epigenetic gene regulation," he added.

The research is reported online in the journal Nature Chemical Biology.