Eukaryotic gene regulation occurs at the chromatin level, which requires changing the chromatin structure by a group of ATP-dependent DNA translocases—namely, the chromatin remodellers¹. In plants, chromatin remodellers function in various biological processes and possess both conserved and plant-specific components^2,3,4,5. DECREASE IN DNA METHYLATION 1 (DDM1) is a plant chromatin remodeller that plays a key role in the maintenance DNA methylation^{6,7,8,9,10,11}. Here we determined the structures of Arabidopsis DDM1 in complex with nucleosome in ADP–BeF_x-bound, ADP-bound and nucleotide-free conformations. We show that DDM1 specifically recognizes the H4 tail and nucleosomal DNA. The conformational differences between ADP–BeF_x-bound, ADP-bound and nucleotide-free DDM1 suggest a chromatin remodelling cycle coupled to ATP binding, hydrolysis and ADP release. This, in turn, triggers conformational changes in the DDM1-bound nucleosomal DNA, which alters the nucleosome structure and promotes DNA sliding. Together, our data reveal the molecular basis of chromatin remodelling by DDM1.

真核基因调控发生在染色质水平，这需要通过一组 ATP 依赖性 DNA 转位酶（即染色质重塑酶）来改变染色质结构¹。在植物中，染色质重塑因子在各种生物过程中发挥作用，并拥有保守的和植物特有的成分^2,3,4,5。DNA 甲基化减少 1 (DDM1) 是一种植物染色质重塑剂，在维持 DNA 甲基化中发挥关键作用^{6,7,8,9,10,11}。在这里，我们确定了拟南芥DDM1 与核小体复合物的 ADP-BeF _x结合、ADP 结合和无核苷酸构象的结构。我们证明 DDM1 特异性识别 H4 尾和核小体 DNA。_{ADP-BeF x}结合、ADP 结合和无核苷酸 DDM1之间的构象差异表明染色质重塑循环与 ATP 结合、水解和 ADP 释放耦合。这反过来又触发 DDM1 结合核小体 DNA 的构象变化，从而改变核小体结构并促进 DNA 滑动。总之，我们的数据揭示了 DDM1 染色质重塑的分子基础。