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. Involved in down-regulation of MYB- and JUN-dependent transcription. Enhances ligand-dependent transcriptional activity of nuclear hormone receptors. May play a role in cell differentiation. Homodimer. Component of the CCR4-NOT complex. Belongs to the CNOT9 family.