Chromatin structure is a key regulator of DNA transcription, replication, and repair¹. In humans, the TIP60/EP400 complex (TIP60-C) is a 20-subunit assembly that impacts chromatin structure via two enzymatic activities: ATP-dependent exchange of histone H2A/H2B for H2A.Z/H2B and histone acetylation, which in yeast are carried out by two independent complexes, SWR1 and NuA4, respectively^2,3. How these activities are merged in humans into one super-complex and what this association entails for their structure, mechanism and recruitment to chromatin is unknown. Here we describe the 2.4-3.3 Å resolution structure of the endogenous human TIP60-C. We find a three lobed architecture composed of SWR1-like (SWR1L) and NuA4-like (NuA4L) parts, that associate with a TRRAP activator-binding module. The huge EP400 subunit harbors the ATPase motor, traverses twice the junction between SWR1L and NuA4L, and constitutes the scaffold of the three-lobed architecture. NuA4L is completely re-arranged compared to its yeast counterpart. TRRAP is flexibly tethered to NuA4L, in stark contrast to its robust connection to the complete opposite side of yeast NuA4^4-7. A modeled nucleosome bound to SWR1L, supported by activity tests, suggests that some aspects of the histone exchange mechanism diverge from the yeast example^8,9. Furthermore, a fixed actin module, as opposed to the mobile actin subcomplex in SWR1⁸, the flexibility of TRRAP and the weak effect of extra-nucleosomal DNA on exchange activity, lead to a different, activator-based, mode of enlisting TIP60-C to chromatin.

染色质结构是 DNA 转录、复制和修复的关键调节因子¹。在人类中，TIP60/EP400 复合物 （TIP60-C） 是一个由 20 个亚基组成的组装体，通过两种酶促活性影响染色质结构：ATP 依赖性组蛋白 H2A/H2B 与 H2A 的交换。Z/H2B 和组蛋白乙酰化，在酵母中分别由两个独立的复合物 SWR1 和 NuA4 进行^2,3。这些活动如何在人类中合并成一个超级复合物，以及这种关联对它们的结构、机制和染色质募集意味着什么，目前尚不清楚。在这里，我们描述了内源性人 TIP60-C 的 2.4-3.3 Å 分辨率结构。我们发现了一个由 SWR1 样 （SWR1L） 和 NuA4 样 （NuA4L） 部分组成的三叶结构，它们与 TRRAP 激活剂结合模块相关联。巨大的 EP400 亚基包含 ATP 酶电机，穿过 SWR1L 和 NuA4L 之间连接处的两倍，并构成了三叶结构的支架。与酵母相比，NuA4L 完全重新排列。TRRAP 可灵活地与 NuA4L 相连，这与它与酵母 NuA4^4-7 完全相反的紧密连接形成鲜明对比。与活性测试结合的建模核小体与 SWR1L 结合，表明组蛋白交换机制的某些方面与酵母示例不同^8,9。此外，与 SWR1⁸ 中的移动肌动蛋白亚复合物相反，固定的肌动蛋白模块、TRRAP 的灵活性和核小体外 DNA 对交换活性的微弱影响，导致了一种不同的、基于激活剂的模式，将 TIP60-C 吸收到染色质上。