3'-exoribonuclease that has a preference for poly(A) tails of mRNAs, thereby efficiently degrading poly(A) tails. Exonucleolytic degradation of the poly(A) tail is often the first step in the decay of eukaryotic mRNAs and is also used to silence certain maternal mRNAs translationally during oocyte maturation and early embryonic development. Interacts with both the 3'-end poly(A) tail and the 5'-end cap structure during degradation, the interaction with the cap structure being required for an efficient degradation of poly(A) tails. Involved in nonsense-mediated mRNA decay, a critical process of selective degradation of mRNAs that contain premature stop codons. Also involved in degradation of inherently unstable mRNAs that contain AU-rich elements (AREs) in their 3'-UTR, possibly via its interaction with KHSRP. Probably mediates the removal of poly(A) tails of AREs mRNAs, which constitutes the first step of destabilization (By similarity). Also able to recognize poly(A) tails of microRNAs such as MIR21 and H/ACA box snoRNAs (small nucleolar RNAs) leading to microRNAs degradation or snoRNA increased stability (By similarity). Exonucleolytic cleavage of poly(A) to 5'-AMP. Divalent metal cations. Mg(2+) is the most probable. Homodimer. Found in a mRNA decay complex with RENT1, RENT2 and RENT3B. Interacts with KHSRP. Interacts with CELF1/CUGBP1. Interacts with ZC3HAV1 in an RNA-independent manner. Interacts with DHX36. Some nuclear fraction is nucleolar. Phosphorylation by MAPKAPK2, preventing GADD45A mRNA degradation after genotoxic stress. Belongs to the CAF1 family.