Chromatin interaction component of the NuA4 histone acetyltransferase complex which is involved in transcriptional activation of selected genes principally by acetylation of nucleosomal histone H4 and H2A. The NuA4 complex is also involved in DNA repair. Is required for NuA4 complex integrity. Component of the SWR1 complex which mediates the ATP-dependent exchange of histone H2A for the H2A variant H2A.Z leading to transcriptional regulation of selected genes by chromatin remodeling. Component of the INO80 complex which remodels chromatin by shifting nucleosomes and is involved in DNA repair (By similarity). Component of the NuA4 histone acetyltransferase complex, of the INO80 chromatin remodeling complex, and of the SWR1 chromatin remodeling complex. Belongs to the actin family. ARP4 subfamily.