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. ARP4 recognizes H2AS128ph (gamma-H2A) and is required for NuA4 complex integrity. Component of the SWR1 complex which mediates the ATP-dependent exchange of histone H2A for the H2A variant HZT1 leading to transcriptional regulation of selected genes by chromatin remodeling. Component of the INO80 complex which remodels chromatin by shifting nucleosomes. Its ability to induce transcription of some phosphate-responsive genes is modulated by inositol polyphosphates. The INO80 complex is involved in DNA repair by associating to gamma-H2A as a response to DNA damage. Component of the NuA4 histone acetyltransferase complex composed of at least ACT1, ARP4, EAF3, EAF5, EAF6, EAF7, EPL1, ESA1, SWC4, TRA1, VID21, YAF9 and YNG2. Component of the chromatin-remodeling INO80 complex, at least composed of ARP4, ARP5, ARP8, RVB1, RVB2, TAF14, NHP10, IES1, IES3, IES4, IES6, ACT1, IES2, IES5 and INO80. Component of the SWR1 chromatin remodeling complex composed of at least ACT1, ARP4, RVB1, RVB2, ARP6, YAF9, VPS71, VPS72, SWC3, SWC4, SWC5, SWC7 and SWR1, and perhaps BDF1. Interacts with histones H4 (HHF1 and HHF2), H3 (HHT1 and HHT2) and H2A (HTA1 and HTA2). Present with 1070 molecules/cell in log phase SD medium. Belongs to the actin family. ARP4 subfamily.