Poliadenilasyon

Poliadenilasyon is a crucial post-transcriptional modification process in eukaryotic gene expression. It involves the addition of a tail of adenine nucleotides, known as a poly(A) tail, to the 3' end of messenger RNA (mRNA) molecules. This process is carried out by a multiprotein complex called the polyadenylation machinery, which recognizes a specific sequence element, the AAUAAA hexanucleotide, downstream of the cleavage site in the pre-mRNA.

The poly(A) tail plays several vital roles in mRNA function. Firstly, it protects the mRNA from degradation by exonucleases in the cytoplasm, thereby increasing its stability and lifespan. Secondly, the poly(A) tail is essential for the efficient export of mRNA from the nucleus to the cytoplasm, where protein synthesis occurs. Thirdly, it plays a role in the initiation of translation by interacting with proteins involved in ribosome binding. The length of the poly(A) tail can also influence the rate of translation and mRNA degradation, providing an additional layer of gene regulation. Aberrations in poliadenilasyon can lead to various cellular dysfunction and diseases.