PUM2 and breast cancer: Transcripts alternatively regulated by the CCR4-NOT catalytic subunit CNOT7 in metastatic mouse mammary cancer cell lines were highly enriched for mRNAs containing the canonical binding elements for the RNA-binding proteins (RNA-BPs) NANOS1, PUMILLIO2 (PUM2), and cleavage and polyadenylation specific factor 4 (CPSF4) (Fig. 1a).