The goal of this proposal is the design, synthesis and testing of inhibitors of Histone Lysine Methyltransferases. We will design HKMTs focused libraries based on available crystal structure information. Initially we will target the S-adenosyl methionine (SAM) binding site, since it offers the opportunity to identify inhibitors of different HKMTs. The crystal structures reveal several interesting features of this site7. The adenine moiety of SAM binds to a well defined pocket engaging in hydrogen bonds. Importantly, the rest of the molecule adopts a conformation that has not been observed for other SAM utilising enzymes, suggesting that mimicking this conformation will lead to inhibitors specific for HMKTs. Moreover, a recently published analysis concludes that the co-factor binding sites of HKMTs are druggable and can be explored to give selective inhibitors. To identify HKMT inhibitors that can compete with SAM we will initially designand synthesise inhibitors that mimic the adenine moiety. Initially, we will keep the molecular weight of these compounds relatively low (<350). Again these compounds will be tested and the most promising representative will be co-crystallised. The co-crystal structure then serves as the starting point for more advanced and potent compounds. The testing against selected HKMTs will be done using commercially available assay kits9. In addition, LCMS or Caliper based detection of HKMT substrates have already been established at the Unit and can be explored. The internal testing will be complemented with external profiling at appropriate vendors e.g. to profile advanced compounds against a larger ranges of HKMTs. The crystallography will be conducted with an external collaborator.