Has 3'-5' poly(A) exoribonuclease activity for synthetic poly(A) RNA substrate. 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. May be involved in the deadenylation-dependent degradation of mRNAs through the 3'-UTR AU-rich element-mediated mechanism. Involved in deadenylation-dependent degradation of CDKN1B mRNA. Its mRNA deadenylase activity can be inhibited by TOB1. Mediates cell proliferation and cell survival and prevents cellular senescence. Exonucleolytic cleavage of poly(A) to 5'-AMP. Binds 2 magnesium ions, but the ions interact each with only 1 or 2 residues. Inhibited by free AMP, and with lesser efficiency also by CMP, GMP, UMP, ATP and neomycin. Component of the CCR4-NOT complex; distinct complexes seem to exist that differ in the participation of probably mutually exclusive catalytic subunits; the complex contains two deadenylase subunits, CNOT6 or CNOT6L, and CNOT7 or CNOT8 (PubMed:17452450, PubMed:18377426, PubMed:19558367). Interacts with CNOT1, CNOT3, CNOT7, CNOT8 and CNOT9 (PubMed:17452450). Interacts with TOB1 (PubMed:18377426). Interacts with NANOS2 (By similarity). Interacts with ZFP36 (By similarity). Predominantly cytoplasmic. Highly expressed in placenta, skeletal muscle, pancreas, testis and leukocytes. Weakly expressed in heart, spleen and thymus. Depletion of CNOT6L causes cell growth defect. Belongs to the CCR4/nocturin family.