May regulate cell growth likely by suppressing RB1 phosphorylation (PubMed:19531561). May function as RNase and regulate the levels of target RNA species (Potential). In association with ZC3H12A enhances the degradation of interleukin IL-6 mRNA level in activated macrophages (PubMed:26134560). Serve as a tumor suppressor in certain leukemia cells (PubMed:17210687). Overexpression inhibits the G1 to S phase progression through suppression of RB1 phosphorylation (PubMed:19531561). {ECO:0000269|PubMed:17210687, ECO:0000269|PubMed:19531561, ECO:0000269|PubMed:26134560, ECO:0000305}. This is the function of Ensembl gene identifier ENSG00000178199 (ZC3H12D, zinc finger CCCH-type containing 12D).