Anti-proliferative protein; the function is mediated by association with deadenylase subunits of the CCR4-NOT complex. Mediates CPEB3-accelerated mRNA deadenylation by binding to CPEB3 and recruiting CNOT7 which leads to target mRNA deadenylation and decay. Interacts with ERBB2. Interacts with CNOT7. Interacts with CPEB3 (via C-terminal RNA-binding region); recruits CNOT7 to CPEB3 to form a ternary complex required for mRNA deadenylation and decay. Interacts with CNOT8. Interacts with CPEB4. Only a small fraction localizes to the cytoplasm except in late S-phase where more than half of proteins become cytoplasmic. Ubiquitous. Phosphorylated on Ser and Thr residues. Belongs to the BTG family.