<p>Members of this family encode proteins with methylase activity. The enzyme activity has been mapped to the SET domain [<cite idref="PUB00014615"/>], originally identified in <taxon tax_id="7227">Drosophila melanogaster</taxon> (Fruit fly) Su(var)3-9, E(z) and Trithorax proteins [<cite idref="PUB00007132"/>].</p> <p>The sequence conservation pattern and structural analysis of the SET domain provides clues regarding possible active site residues. There are three conserved sequence motifs in most of the SET domain, two of which had been reported earlier. The N-terminal motif (I) has characteristic glycines. The central motif (II) has a distinct pattern of polar and charged residues (Asn, His). The C-terminal motif (III) has a characteristic dyad of polar residues and the hydrophobic residue tyrosine.</p> <p>The Trithorax group of proteins has been implicated in a variety of processes, including centromeric and telomeric silencing and cell-cycle regulation [<cite idref="PUB00014616"/>].</p> Methyltransferase, trithorax