Binds double-stranded RNA and both single-stranded and double-stranded DNA. In oocytes, expression is limited to the germinal vesicle with highest levels in the nucleolus although a considerable portion is present in other regions of the germinal vesicle. In oocytes that progress to the first meiotic metaphase, diffuse expression is observed throughout the egg cytoplasm. Expressed specifically in the oocytes of the ovaries. Expressed maternally in immature oocytes at high levels but is scarcely detectable in mature oocytes or in embryos at the morula and blastula stages. Phosphorylation occurs in oocytes during the progression of the first meiotic M phase. No phosphorylation is observed in immature oocytes. Belongs to the nucleoplasmin family.