Bromodomain; ASH1_like sub-family. ASH1 (absent, small, or homeotic 1) is a member of the trithorax-group in Drosophila melanogaster, an epigenetic transcriptional regulator of HOX genes. Drosophila ASH1 has been shown to methylate specific lysines in histones H3 and H4. Mammalian ASH1 has been shown to methylate histone H3. Bromodomains are 110 amino acid long domains, that are found in many chromatin associated proteins. Bromodomains can interact specifically with acetylated lysine.