Ubiquitination-dependent histone crosstalk plays critical roles in chromatin-associated processes and is highly associated with human diseases. Mechanism studies of the crosstalk have been of the central focus. Here our study on the crosstalk between H2BK34ub and Dot1L-catalyzed H3K79me suggests a novel mechanism of ubiquitination-induced nucleosome distortion to stimulate the activity of an enzyme. We determined the cryo-electron microscopy structures of Dot1L–H2BK34ub nucleosome complex and the H2BK34ub nucleosome alone. The structures reveal that H2BK34ub induces an almost identical orientation and binding pattern of Dot1L on nucleosome as H2BK120ub, which positions Dot1L for the productive conformation through direct ubiquitin–enzyme contacts. However, H2BK34-anchored ubiquitin does not directly interact with Dot1L as occurs in the case of H2BK120ub, but rather induces DNA and histone distortion around the modified site. Our findings establish the structural framework for understanding the H2BK34ub–H3K79me trans-crosstalk and highlight the diversity of mechanisms for histone ubiquitination to activate chromatin-modifying enzymes.

泛素化依赖性组蛋白串扰在染色质相关过程中起着关键作用，并且与人类疾病高度相关。串扰的机制研究一直是中心焦点。在这里，我们对 H2BK34ub 和 Dot1L 催化的 H3K79me 之间串扰的研究表明泛素化诱导的核小体变形刺激酶活性的新机制。我们确定了 Dot1L–H2BK34ub 核小体复合物和单独的 H2BK34ub 核小体的冷冻电子显微镜结构。结构显示 H2BK34ub 诱导 Dot1L 在核小体上的方向和结合模式与 H2BK120ub 几乎相同，这通过直接泛素-酶接触将 Dot1L 定位为生产性构象。然而，H2BK34 锚定泛素不像 H2BK120ub 那样直接与 Dot1L 相互作用，而是在修饰位点周围诱导 DNA 和组蛋白变形。我们的研究结果建立了理解 H2BK34ub–H3K79me 的结构框架反式串扰并突出显示组蛋白泛素化激活染色质修饰酶的机制的多样性。