Epizyme Inc., 325 Vassar Street, Cambridge, MA 02139, USA.
Chem Biol Drug Des. 2012 Dec;80(6):971-80. doi: 10.1111/cbdd.12050. Epub 2012 Oct 9.
DOT1L is the human protein methyltransferase responsible for catalyzing the methylation of histone H3 on lysine 79 (H3K79). The ectopic activity of DOT1L, associated with the chromosomal translocation that is a universal hallmark of MLL-rearranged leukemia, is a required driver of leukemogenesis in this malignancy. Here, we present studies on the structure-activity relationship of aminonucleoside-based DOT1L inhibitors. Within this series, we find that improvements in target enzyme affinity and selectivity are driven entirely by diminution of the dissociation rate constant for the enzyme-inhibitor complex, leading to long residence times for the binary complex. The biochemical K(i) and residence times measured for these inhibitors correlate well with their effects on intracellular H3K79 methylation and MLL-rearranged leukemic cell killing. Crystallographic studies reveal a conformational adaptation mechanism associated with high-affinity inhibitor binding and prolonged residence time; these studies also suggest that conformational adaptation likewise plays a critical role in natural ligand interactions with the enzyme, hence, facilitating enzyme turnover. These results provide critical insights into the role of conformational adaptation in the enzymatic mechanism of catalysis and in pharmacologic intervention for DOT1L and other members of this enzyme class.
DOT1L 是一种人类蛋白甲基转移酶，负责催化组蛋白 H3 赖氨酸 79（H3K79）的甲基化。与 MLL 重排白血病普遍特征相关的染色体易位导致 DOT1L 的异位活性，是这种恶性肿瘤发生白血病的必需驱动因素。在这里，我们研究了基于氨基核苷的 DOT1L 抑制剂的结构-活性关系。在这个系列中，我们发现对靶酶亲和力和选择性的提高完全是由于酶-抑制剂复合物的解离速率常数的降低，导致二元复合物的停留时间延长。这些抑制剂的生化 K(i)和停留时间与它们对细胞内 H3K79 甲基化和 MLL 重排白血病细胞杀伤的影响很好地相关。晶体学研究揭示了与高亲和力抑制剂结合和延长停留时间相关的构象适应机制；这些研究还表明，构象适应同样在酶与天然配体的相互作用中起着关键作用，从而促进酶的周转。这些结果为构象适应在催化酶的酶促机制以及 DOT1L 和该酶类别的其他成员的药物干预中的作用提供了重要的见解。
