Acts as a chaperone for the linker histone to facilitate deposition of histone B4 onto linker DNA. Required for both remodeling of sperm chromatin into nucleosomes, and linker histone binding to nucleosome core dimers. Plays a role in tissue-specific gene regulation. Required for primitive hemopoiesis, acting upstream of tal1/scl. Forms homomultimers. Interacts with histone B4. Interacts with the B-type cyclins ccnb1 and ccnb2. Cytoplasmic prior to the midblastula transition, becoming predominantly nuclear subsequently. Initially expressed throughout the embryo with expression higher at the animal pole. Becomes localized to presumptive ectoderm by gastrula stages. By stage 18 (neurula), expressed in the neural plate and posterior to the cement gland. In late neurula/early tailbud stages, expressed in the neural crest, neural tube, eyes, tailbud and ventral blood islands. Adult expression is predominantly in ovaries. Expressed both maternally and zygotically. Expression levels remain constant during embryonic development, increasing at the swimming tadpole stage. The acidic domains are probably involved in the interaction with histones. Phosphorylated by cyclin B-cdc2 kinase complexes. Belongs to the nucleosome assembly protein (NAP) family. C-terminus does not match that of displayed sequence.