组蛋白H2A变体H2A。W占据转座子,因此在拟南芥中阻止了对它们的访问。H2A.W由染色质重塑剂DDM1沉积,这也通过未知的机制促进染色质作者对异染色质的可及性。为了阐明这个问题,我们求解了含有H2A和H2A的核小体的低温EM结构。W,还有DDM1-H2A.W核小体复合物。这些结构显示H2A核小体的DNA末端柔性高于H2A。W核小体。在DDM1-H2A中。W核小体复合物,DDM1与H4的N末端尾部和核小体DNA结合,并增加H2A的DNA末端柔性。W核小体。基于这些生化和结构结果,我们建议DDM1对抗含有H2A的核小体引起的低可及性。W能够维持转座子上的抑制性表观遗传标记并防止其活性。
The histone H2A variant H2A.W occupies transposons and thus prevents access to them in Arabidopsis thaliana. H2A.W is deposited by the chromatin remodeler DDM1, which also promotes the accessibility of chromatin writers to heterochromatin by an unknown mechanism. To shed light on this question, we solve the cryo-EM structures of
nucleosomes containing H2A and H2A.W, and the DDM1-H2A.W nucleosome complex. These structures show that the DNA end flexibility of the H2A nucleosome is higher than that of the H2A.W nucleosome. In the DDM1-H2A.W nucleosome complex, DDM1 binds to the N-terminal tail of H4 and the nucleosomal DNA and increases the DNA end flexibility of H2A.W
nucleosomes. Based on these biochemical and structural results, we propose that DDM1 counters the low accessibility caused by
nucleosomes containing H2A.W to enable the maintenance of repressive epigenetic marks on transposons and prevent their activity.