A second catalytic domain in the Elp3 histone acetyltransferases: a candidate for histone demethylase activity?

A new subfamily of two-domain histone acetyltransferases (HATs) related to Elp3 has been identified. In addition to a HAT domain in the C terminus, these proteins have an N-terminal domain similar to the catalytic domain of S-adenosylmethionine radical enzymes. Two-domain organization is preserved in evolution, suggesting that both enzymatic activities are functionally or mechanistically coupled and directed towards highly conserved substrates. The functional implications of this similarity and a possible role for Elp3-related proteins as histone demethylases are discussed.