Involved in the 3'-end formation of mRNA precursors (pre-mRNA) by the addition of a poly(A) tail of 200-250 nt to the upstream cleavage product. Stimulates poly(A) polymerase (PAPOLA) conferring processivity on the poly(A) tail elongation reaction and controls also the poly(A) tail length. Increases the affinity of poly(A) polymerase for RNA. Binds to poly(A) and to poly(G) with high affinity. May protect the poly(A) tail from degradation. Monomer and homooligomer. Binds RNA as a monomer and oligomerizes when bound to poly(A) (By similarity). Shuttles between the nucleus and the cytoplasm but predominantly found in the nucleus. Shows dynamic spatial expression throughout development. First expressed in the animal pole region of the egg and this pattern persists through to the blastula stage. In gastrula and neurula embryos, expressed mainly in ectodermal, neural and epidermal regions. Neural tissue-specific expression pattern persists into tailbud stage when expression is localized to the brain and spinal cord. At early tadpole stage, expression becomes gradually confined to the specific vesicle regions of the developing brain. At stage 39, expressed in the telencephalon and mesencephalon regions of the brain. Also detected in the eye and olfactory pit at the tadpole stage. Expressed during gut endoderm development. At stage 35, expressed exclusively in the anterior portion of the gut endoderm, which includes the prospective liver, stomach and pancreas. As development proceeds, expression becomes restricted to the pancreas, and by stage 46/47 (the seventh day of development) expression is localized exclusively to the pancreas. Expressed in most adult tissues. Expressed both maternally and zygotically. Expressed at relatively constant levels throughout development. The RRM domain is essential for specific adenine bases recognition in the poly(A) tail but not sufficient for poly(A) binding.