Practice question

After cleavage at polyadenylation site, polyadenine tail is synthesized not by RNA polymerase II but by specialized nuclear polyadenine polymerase PAPOLA and PAPOLG, recruited through interaction with CPSF via FIP1 subunit and stimulated by nuclear polyadenine binding protein PABPN1. Enzyme is template independent, uses ATP to add adenylates processively: initial distributive addition of ten to twelve adenines, then PABPN1-dependent switch to processive synthesis of two hundred to two hundred fifty residues in mammals. Polyadenine tail enhances stability, export, and translation via PABPC and eIF4G circularization bridge.