Protein lysine methyltransferases (PKMTs) regulate diverse physiological processes including transcription and the maintenance of genomic integrity. Genetic studies suggest that the PKMTs SUV420H1 and SUV420H2 facilitate proficient nonhomologous end-joining (NHEJ)-directed DNA repair by catalyzing the di- and trimethylation (me2 and me3, respectively) of lysine 20 on histone 4 (H4K20). Here we report the identification of A-196, a potent and selective inhibitor of SUV420H1 and SUV420H2. Biochemical and co-crystallization analyses demonstrate that A-196 is a substrate-competitive inhibitor of both SUV4-20 enzymes. In cells, A-196 induced a global decrease in H4K20me2 and H4K20me3 and a concomitant increase in H4K20me1. A-196 inhibited 53BP1 foci formation upon ionizing radiation and reduced NHEJ-mediated DNA-break repair but did not affect homology-directed repair. These results demonstrate the role of SUV4-20 enzymatic activity in H4K20 methylation and DNA repair. A-196 represents a first-in-class chemical probe of SUV4-20 to investigate the role of histone methyltransferases in genomic integrity.
Authors: Kenneth D Bromberg, Taylor R H Mitchell, Anup K Upadhyay, Clarissa G Jakob, Manisha A Jhala, Kenneth M Comess, Loren M Lasko, Conglei Li, Creighton T Tuzon, Yujia Dai, Fengling Li, Mohammad S Eram, Alexander Nuber, Niru B Soni, Vlasios Manaves, Mikkel A Algire, Ramzi F Sweis, Maricel Torrent, Gunnar Schotta, Chaohong Sun, Michael R Michaelides, Alex R Shoemaker, Cheryl H Arrowsmith, Peter J Brown, Vijayaratnam Santhakumar, Alberto Martin, Judd C Rice, Gary G Chiang, Masoud Vedadi, Dalia Barsyte-Lovejoy, William N Pappano