Poly(A) nuclease with 3'-5' RNase activity. Catalytic component of the CCR4-NOT complex which is one of the major cellular mRNA deadenylases and is linked to various cellular processes including bulk mRNA degradation, miRNA-mediated repression, translational repression during translational initiation and general transcription regulation. Additional complex functions may be a consequence of its influence on mRNA expression (By similarity). Exonucleolytic cleavage of poly(A) to 5'-AMP. Binds 2 magnesium ions, but the ions interact each with only 1 or 2 residues. Component of the CCR4-NOT complex. Predominantly cytoplasmic. Belongs to the CCR4/nocturin family.