The 3' tailing process, formally known as polyadenylation, is a fundamental step in the maturation of messenger RNA (mRNA) molecules in eukaryotic cells. It specifically involves modifications that occur at the 3' end of the initial RNA transcript, called pre-mRNA.
Based on the provided reference, the process of tailing is defined as the "cleavage of the 3' end and addition of adenylate residues to the same end of the pre-mRNA".
This definition breaks down the process into two main actions:
- Cleavage at the 3' End: A specific section near the end of the newly synthesized pre-mRNA molecule is cut off.
- Addition of Adenine Nucleotides: Following this cleavage, a long chain of adenine nucleotides (called a poly(A) tail) is attached to the newly exposed 3' end.
The Polyadenylation Signal Sequence
A crucial element that directs this process is a specific sequence found within the pre-mRNA. The reference highlights that a conserved sequence 5'-AAUAAA-3' is typically present near the 3' end of the primary transcript. This sequence acts as a polyadenylation signal, indicating where the cleavage and subsequent addition of the poly(A) tail should occur.
In summary, the 3' tailing process creates a poly(A) tail on the mRNA, which is essential for the molecule's stability, transport from the nucleus to the cytoplasm, and efficient translation into protein.
