Drosophila SWR1 and NuA4 complexes are defined by DOMINO isoform

Histone acetylation and deposition of H2A.Z variant are integral aspects of active transcrip-tion. In Drosophila, the single DOMINO chromatin regulator complex is thought to combine both activities via an unknown mechanism. Here we show that alternative isoforms of the DOMINO nucleosome remodeling ATPase, DOM-A and DOM-B, directly specify two distinct multi-subunit complexes. Both complexes are necessary for transcriptional regulation but through different mechanisms. The DOM-B complex incorporates H2A.V (the fly ortholog of H2A.Z) genome-wide in an ATP-dependent manner, like the yeast SWR1 complex. The DOM-A complex, instead, functions as an ATP-independent histone acetyltransferase com-plex similar to the yeast NuA4, targeting lysine 12 of histone H4. Our work provides an in-structive example of how different evolutionary strategies lead to similar functional separation. In yeast and humans, nucleosome remodeling and histone acetyltransferase complexes orig-inate from gene duplication and paralog specification. Drosophila generates the same diversi-ty by alternative splicing of a single gene.