Structure and Flexibility of the Yeast NuA4 Histone Acetyltransferase Complex

The NuA4 protein complex acetylates histones H4 and H2A to activate both transcription and DNA repair. We report the 3.0 Å-resolution cryo-electron microscopy structure of the central hub of NuA4, which flexibly tethers the HAT and TINTIN modules. The hub contains the large Tra1 subunit and a core that includes Swc4, Arp4, Act1, Eaf1 and the C-terminal region of Epl1. Eaf1 stands out as the primary scaffolding factor that interacts with the Tra1, Sw4 and Epl1 subunits and contributes the conserved HSA helix to the Arp module. Using nucleosome binding assays, we find that the HAT module, which is anchored to the core through Epl1, recognizes H3K4me3 nucleosomes with hyperacetylated H3 tails, while the TINTIN module, anchored to the core via Eaf1, recognizes nucleosomes that have hyperacetylated H2A and H4 tails. Together with the known interaction of Tra1 with site-specific transcription factors, our data suggests a model in which Tra1 recruits NuA4 to specific genomic sites then allowing the flexible HAT and TINTIN modules to select nearby nucleosomes for acetylation. ### Competing Interest Statement Matthew R. Marunde and Irina K. Popova are employees at EpiCypher. EpiCypher is a commercial developer and supplier of reagents (e.g. PTM-defined semi-synthetic nucleosomes; dNucs) and platforms (dCypher) used in this study.