Biochemical crosstalk between two or more histone modifications is often observed in epigenetic enzyme regulation, but its functional significance in cells has been difficult to discern. Previous enzymatic studies revealed that Lys14 acetylation of histone H3 can inhibit Lys4 demethylation by lysine-specific demethylase 1 (LSD1). In the present study, we engineered a mutant form of LSD1, Y391K, which renders the nucleosome demethylase activity of LSD1 insensitive to Lys14 acetylation. K562 cells with the Y391K LSD1 CRISPR knockin show decreased expression of a set of genes associated with cellular adhesion and myeloid leukocyte activation. Chromatin profiling revealed that the cis-regulatory regions of these silenced genes display a higher level of H3 Lys14 acetylation, and edited K562 cells show diminished H3 mono-methyl Lys4 near these silenced genes, consistent with a role for enhanced LSD1 demethylase activity. These findings illuminate the functional consequences of disconnecting histone modification crosstalk for a key epigenetic enzyme.

在表观遗传酶调控中经常观察到两个或多个组蛋白修饰之间的生化串扰，但其在细胞中的功能意义一直难以辨别。先前的酶学研究表明，组蛋白 H3 的 Lys14 乙酰化可以抑制赖氨酸特异性去甲基化酶 1 （LSD1） 的 Lys4 去甲基化。在本研究中，我们设计了 LSD1 的突变形式 Y391K，它使 LSD1 的核小体去甲基化酶活性对 Lys14 乙酰化不敏感。具有 Y391K LSD1 CRISPR 敲入的 K562 细胞显示一组与细胞粘附和髓系白细胞活化相关的基因表达降低。染色质分析显示，这些沉默基因的顺式调控区域显示出更高水平的 H3 Lys14 乙酰化，编辑的 K562 细胞显示这些沉默基因附近的 H3 单甲基化 Lys4 减少，这与增强 LSD1 去甲基化酶活性的作用一致。这些发现阐明了断开关键表观遗传酶的组蛋白修饰串扰的功能后果。