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. Also plays an essential role in the nucleocytoplasmic transport of specific mRNAs via the uncommon nuclear mRNA export receptor XPO1/CRM1. Interacts with histones H3 and H4. Interacts with KLF5; this interaction induces promoter region-specific histone incorporation and inhibition of histone acetylation by ANP32B. Histone binding is mediated by the concave surface of the LRR region. Directly cleaved by caspase-3/CASP3. Belongs to the ANP32 family.