Transcriptional coactivator involved in neuroepithelial stem cell differentiation and neurogenesis. Involved in particular in lens epithelial cell gene regulation and stress responses. May play an important role in lens epithelial to fiber cell terminal differentiation. May play a protective role during stress-induced apoptosis (By similarity). Monomer (By similarity). Interacts with IFRD1/PC4 (By similarity). Interacts (via IBD domain) with POGZ (via IBM motif) and CDCA7L (via IBM motifs) (By similarity). Interacts (via IBD domain) with KMT2A (via IBM motifs) with a moderate affinity whereas interacts with the KMT2A-MEN1 complex with a greater affinity; MEN1 enhances interaction of KMT2A with PSIP1 (By similarity). Interacts (via IBD domain) with IWS1 (via IBM motif), MED1 (via IBM motif) and DBF4 (via IBM motifs) (By similarity). (Microbial infection) Interacts (via IBD domain) with feline immunodeficiency virus (FIV) integrase (IN), determining its nuclear localization, its tight association with chromatin and its protection from the proteasome. Citrullinated by PADI4. Belongs to the HDGF family.