Practice question

Polyadenylation of eukaryotic messenger RNA occurs exclusively at three prime end, downstream of AAUAAA signal where nascent RNA is cleaved by endonuclease CPSF73. Polyadenylate polymerase PAP adds continuous stretch of adenine residues to new three hydroxyl group in template-independent manner using ATP. Location exclusively three prime is critical for defining messenger RNA orientation, promoting nuclear export, protecting against three prime to five prime exosome decay, and enhancing translation initiation via interaction between polyadenine binding protein PABPC and eIF4G that circularizes mRNA. Replication-dependent histone mRNAs are exception lacking polyadenylation.