The trithorax-group gene in Drosophila little imaginal discs encodes a trimethylated histone H3 Lys4 demethylase.

Histone H3 Lys4 (H3K4) is methylated by yeast Set1-COMPASS and its mammalian homolog, the MLL complex. Human JARID1d can demethylate trimethyl-H3K4 (H3K4me3). We identified Drosophila melanogaster little imaginal discs (Lid) as the JARID1d homolog. We report that Lid knockdown using RNA interference results in a specific genome-wide increase in H3K4me3 levels without affecting other patterns of H3 methylation, and results in an altered distribution of the chromo-helicase protein Chd1.