Essential protein (PubMed:19956626). Polymerase that creates the 3'-poly(A) tail of mRNA's (PubMed:15297145). Also required for the endoribonucleolytic cleavage reaction at some polyadenylation sites. May acquire specificity through interaction with a cleavage and polyadenylation specificity factor (CPSF) at its C-terminus (By similarity). ATP + RNA(n) = diphosphate + RNA(n)-3'-adenine ribonucleotide Binds 2 magnesium ions. Also active with manganese. Monomer (By similarity). Forms a complex with cleavage and polyadenylation specificity factor (CPSF) subunits CFIS2, FIPS3, PAPS1, PABN1, PABN2, PABN3 and FIPS5 (PubMed:16282318, PubMed:18479511). Mostly expressed in flowers (very active in pollen, sepals, styles, and stigmas), cotyledons and hypocotyls, and, to a lower extent, in roots (confined to the vascular tissue in the radicle) and leaves (in the vascular tissue and leaf petioles). Barely detected in stems (PubMed:15297145, PubMed:19956626). Active in the primary and secondary root systems (PubMed:19956626). Lethal. Incomplete sequence. Incomplete sequence. Belongs to the poly(A) polymerase family. Truncated N-terminus.