Structural domains comprising this superfamily share the structure of the zinc binding domain (ZZ) of the cytoplasmic polyadenylation element-binding proteins (CPEBs), RNA-binding proteins that are essential regulators of post-transcriptional gene expression. CPEB regulates protein expression by inhibiting polyadenylation of selected mRNA transcripts, which prevents binding of the ribosome for protein synthesis PMID:23500490. Its ZZ domain has shown to be an interaction domain and to have a dual function, as it contributes to increasing the affinity of the RNA recognition motifs (RRMs) for the CPEs and to promotes interactions with other protein factors in the translational repression/activation complexes assembled by CPEBs PMID:24990967.