ING4 is similar to ING1, a tumor suppressor protein that can interact with TP53, inhibit cell growth, and induce apoptosis. ING4 contains a PHD-finger, which is a common motif in proteins involved in chromatin remodeling. ING4 protein can bind TP53 and EP3/p3, a component of the histone acetyltransferase complex, suggesting its involvement in the TP53-dependent regulatory pathway. ING4 is a component of the HBO1 complex which has a histone H4-specific acetyltransferase activity, a reduced activity toward histone H3 and is responsible for the bulk of histone H4 acetylation in vivo. Through chromatin acetylation, it may function in DNA replication. ING4 may also inhibit tumor progression by modulating the transcriptional output of signaling pathways that regulate cell proliferation.