Polyadenylation

Addition of a poly(A) tail to an RNA end. Its effect and regulation depend on the compartment and transcript class.

In many eukaryotic messenger RNAs, cleavage and addition of the tail help establish a mature end and influence export, biological translation and stability. Tail length can subsequently change. Polyadenylation is therefore a processing event whose functional consequence depends on the transcript and system. ^[ref]

The AAUAAA signal is a six-nucleotide RNA sequence involved in cleavage and polyadenylation of many eukaryotic pre-mRNAs. Recognition of the signal helps organize processing downstream, after which a poly(A) tail is added. The signal itself is an encoded part of the RNA; the tail is subsequently synthesized and is not simply a copied run of genomic adenines. ^[ref]

Mutating the signal and comparing processing of defined RNA substrates supplied a direct functional test. The result concerns a particular processing context: other surrounding sequences and protein factors also contribute, and biological polyadenylation sites can use signal variants. Sequence recognition, cleavage position and final tail length are separate features of the mature transcript.