Acts as a chaperonin for the core histones H3, H2B and H4. Associated with nucleolar ribonucleoprotein structures and bind single-stranded nucleic acids. It may function in the assembly and/or transport of ribosome. May stimulate endonuclease activity on apurinic/apyrimidinic (AP) double-stranded DNA. May inhibit endonuclease activity on AP single-stranded RNA (By similarity). Decamer formed by two pentameric rings associated in a head-to-head fashion. Generally nucleolar, but is translocated to the nucleoplasm in case of serum starvation or treatment with anticancer drugs. Phosphorylated. Belongs to the nucleoplasmin family.