Tudor Domains as Methyl-Lysine and Methyl-Arginine Readers

The Tudor domain is a methyl-lysine and methyl-arginine binding domain present in proteins involved in cellular functions as diverse as DNA transcription, RNA metabolism, gene silencing, the transmission of epigenetic posttranslational modifications, and the maintenance of genomic stability. In this chapter, we review the different forms-single Tudor, tandem Tudor, hybrid Tudor, extended Tudor-and substrate binding modes, including methylation-state specificity, of the Tudor domain. Our focus is on proteins for which three-dimensional structures of Tudor domains in complex with lysine- or arginine-methylated substrates are available. The functional significance of Tudor proteins in chromatin signaling and possible involvement in diseases are highlighted.