Structure of the histone acetyltransferase NuA4 complex

Abstract

NuA4, one of two major histone acetyltransferase complexes in Saccharomyces cerevisiae, specifically acetylates histone H4 and H2A, and therefore loosen the histone-DNA contacts, resulting in increased transcriptional activity. Here we present a near-atomic resolution structure of NuA4 complex through cryonic electron microscopy. The structure comprises six subunits and a total of 5,000 amino acids, within which Eaf1 and Eaf2 twist against each other and span from Actin-Arp4 module to the platform subunit Tra1, forming the backbone of NuA4. The locations of four missing components including Yaf9, and Esa1, Yng2 and Eaf6 of Piccolo module were indicated based on the structure. Intriguingly, our biochemical data showed that NuA4 doesnt bind nucleosome in vitro, whereas possesses strong histone acetyltransferase activity. Its Piccolo module, which has long been regarded as the catalytic module of NuA4, acetylates the nucleosome substrate at almost the same efficiency, but is capable of binding nucleosome. Combining the structural and biochemical data give rise to a model in which the entire NuA4 adopts an auto-inhibited conformation, and undergoes structural rearrangements upon substrate and co-factor additions, restoring its capacity of nucleosome-binding and activity of hyper-acetylation.