The last family of SWI-like ATP-dependent chromatin-remodelling complexes is the INO80 family. These complexes contain INO80 ATPases, which in mammals include INO80 and SWR1 and are characterized by the presence of a conserved split ATPase domain. The INO80 and SWR1 complexes are large multisubunit machines with in vitro nucleosome-remodelling activity, which might contribute to their in vivo roles in transcriptional regulation (see ref. 80 for a review). In the light of recent discoveries, we focus on the developmental functions of the SWR1 complex and a related complex known as the TIP60-p400 complex. In yeast, the Swr1 complex incorporates the variant histone Htz1 (known as H2AZ in mammals) into chromatin by replacing H2A81. In mammals, the genes encoding p400 and SRCAP are closely related homologues of yeast SWR1 and the gene products are found in distinct complexes that have common subunits but potentially different functions82. SRCAP-containing complexes are required for the deposition of H2AZ in vivo83, although the role of these complexes in H2AZ incorporation during development has not been studied. H2AZ is conserved from yeast to mammals: how it functions
