The novel lysine methyltransferase ILSE1 controls castration-resistant prostate cancer

表观遗传作家，如组蛋白甲基转移酶，在生理和病理控制中起着关键作用。因此，各种组蛋白甲基转移酶的小分子抑制剂被开发出来，并进入临床评估。为了进一步扩展我们对这类重要的表观遗传酶的分子功能的了解，我们将生物信息学方法，如同源性预测和化学信息学与3D结构信息相结合，以确定具有潜在临床意义的新的组蛋白甲基转移酶(HMTs)。一种有趣的赖氨酸甲基转移酶，此后命名为ILSE1，是一种表观遗传酶，它写着染色质标记组蛋白H4在赖氨酸12(H4K12me)处单甲基化，到目前为止还没有被赋予任何功能。在催化中心引入单点突变或用S-腺苷蛋氨酸竞争性抑制剂新诺明处理在体外可取消ILSE1的甲基化。因此，ILSE1的耗尽或异位表达分别导致培养细胞中H4K12me水平的降低和升高。值得注意的是，ILSE1 RNAi对雄激素依赖和去势抵抗的前列腺癌细胞系的增殖都有最大的损害作用。相反，未转化细胞和各种其他肿瘤细胞的生长不受ILSE1的调控，揭示了前所未有的作用特异性。最后，在小鼠异种移植模型中，ILSE1的缺失导致雄激素依赖和去势抵抗的前列腺癌细胞的生长严重受阻。综上所述，我们的前期工作证明ILSE1是第一个H4K12甲基转移酶，在体外和体内都能强烈地阻碍去势耐药前列腺癌的增殖。因此，我们的数据确定ILSE1是小分子抑制剂潜在的抗去势前列腺癌治疗干预的靶点。因此，我们建议(1)确定ILSE1的三维晶体结构，并利用这些结构信息来设计和表征抑制ILSE甲基转移酶活性的化学探针。我们将(2)通过鉴定和鉴定靶基因来揭示ILSE1在生理和病理中的功能。最后，我们计划(3)通过鉴定阅读器和橡皮擦蛋白来确定染色质标记H4K12me中存储的信息如何被解释并转化为生理和病理特征。

Epigenetic writers such as histone methyltransferases play key roles in the control of physiology and pathology. Consequently, small molecule inhibitors of various histone methyltransferases have been developed and entered clinical evaluation. To further expand our knowledge on the molecular functions of this important class of epigenetic enzymes we combined bioinformatic approaches such as homology prediction and cheminformatics with 3D structural information to identify novel histone methyltransferases (HMTs) with putative clinical relevance. One of the interesting lysine methyltransferases, hereafter named ILSE1 presents as an epigenetic enzyme writing the chromatin mark histone H4 monomethylated at lysine 12 (H4K12me) to which no function has been assigned so far. Introduction of a single point mutation in the catalytic center or treatment with the S-adenosyl methionine (SAH)-competitive inhibitor sinefungin abrogates methylation by ILSE1 in vitro. Accordingly, depletion or ectopic expression of ILSE1 results in reduced and elevated H4K12me levels in cultured cells, respectively. Of note, ILSE1 RNAi most robustly impairs proliferation of both androgen-dependent and castration-resistant prostate cancer cell lines. In contrast, growth of non-transformed cells and various other tumor cells is not regulated by ILSE1 uncovering unprecedented specificity of action. Finally, depletion of ILSE1 results in severely retarded growth of androgen-dependent and castration-resistant prostate cancer cell in mouse xenograft models. In summary, our preparatory work demonstrates that ILSE1 is the first H4K12 methyltransferase robustly impairing proliferation of castration-resistant prostate cancer in vitro and in vivo. Thus, our data identify ILSE1 as a target for potential therapeutic intervention of castration-resistant prostate cancer by small molecule inhibitors. Consequently, we propose to (1) determine the 3D crystal structure of ILSE1 and use the structural information to design and characterize chemical probes that inhibit ILSE methyltransferase activity. We shall (2) unravel the function of ILSE1 in physiology and pathology by the identification and characterization of target genes. Finally, we plan to (3) determine how the information stored in the chromatin mark H4K12me is interpreted and transduced into physiological and pathological traits by characterization of reader and eraser proteins.