Multifunctional protein that is involved in the regulation of many processes including cell proliferation, apoptosis, cell cycle progression or transcription. Regulates the proliferation of neuronal stem cells, differentiation of leukemic cells and progression from G1 to S phase of the cell cycle. As negative regulator of caspase-3-dependent apoptosis, may act as an antagonist of ANP32A in regulating tissue homeostasis. Exhibits histone chaperone properties, able to recruit histones to certain promoters, thus regulating the transcription of specific genes. Plays also an essential role in the nucleocytoplasmic transport of specific mRNAs via the uncommon nuclear mRNA export receptor XPO1/CRM1. Participates in the regulation of adequate adaptive immune responses by acting on mRNA expression and cell proliferation.; (Microbial infection) Plays an essential role in influenza A and B viral genome replication. Plays also a role in foamy virus mRNA export from the nucleus to the cytoplasm.
