The function of CNOT8 (CCR4-NOT transcription complex subunit 8, Ensembl gene identifier ENSG00000155508) is as follows. Has 3'-5' poly(A) exoribonuclease activity for synthetic poly(A) RNA substrate. Its function seems to be partially redundant with that of CNOT7. Catalytic component of the CCR4-NOT complex which is linked to various cellular processes including bulk mRNA degradation, miRNA-mediated repression, translational repression during translational initiation and general transcription regulation. During miRNA-mediated repression the complex also seems to act as translational repressor during translational initiation. Additional complex functions may be a consequence of its influence on mRNA expression. Associates with members of the BTG family such as TOB1 and BTG2 and is required for their anti-proliferative activity. {ECO:0000269|PubMed:12771185, ECO:0000269|PubMed:19605561, ECO:0000269|PubMed:20065043, ECO:0000269|PubMed:23236473}.