Why is a 3' polyA tail important for mRNA?

The presence of a 3' polyA tail on mRNA is crucial for its stability and lifespan within the cell. This polyadenylation process adds a series of adenine nucleotides to the 3' end of the mRNA, which protects it from degradation by exonucleases—enzymes that can degrade RNA from the ends. The polyA tail helps enhance the stability of mRNA, preventing it from being broken down quickly, which allows for more efficient translation into proteins.

Furthermore, the polyA tail plays a role in the export of the mRNA from the nucleus to the cytoplasm where translation occurs, and it also influences the initiation of translation by enhancing the binding of initiation factors and ribosomes to the mRNA. Overall, the polyA tail is important for the proper regulation of gene expression at the post-transcriptional level.