ANP32e Binds Histone H2A.Z in a Cell Cycle-Dependent Manner and Regulates Its Protein Stability in the Cytoplasm

ANP32e, a chaperone of H2A.Z, is receiving increasing attention because of its association with cancer growth and progression. An unanswered question is whether ANP32e regulates H2A.Z dynamics during the cell cycle; this could have clear implications for the proliferation of cancer cells. We confirmed that ANP32e regulates the growth of human U2OS cancer cells and preferentially interacts with H2A.Z during the G1 phase of the cell cycle. Unexpectedly, ANP32e does not mediate the removal of H2A.Z from chromatin, is not a stable component of the p400 remodeling complex and is not strongly associated with chromatin. Instead, most ANP32e is in the cytoplasm. Here, ANP32e preferentially interacts with H2A.Z in the G1 phase in response to an increase in H2A.Z protein abundance and regulates its protein stability. This G1-specific interaction was also observed in the nucleoplasm but was unrelated to any change in H2A.Z abundance. These results challenge the idea that ANP32e regulates the abundance of H2A.Z in chromatin as part of a chromatin remodeling complex. We propose that ANP32e is a molecular chaperone that maintains the soluble pool of H2A.Z by regulating its protein stability and acting as a buffer in response to cell cycle-dependent changes in H2A.Z abundance.