3' poly-A tail

Definition

A 3' poly-A tail is a stretch of adenine nucleotides added to the 3' end of a newly synthesized mRNA molecule during post-transcriptional modification. This tail plays crucial roles in stabilizing the mRNA, facilitating its export from the nucleus, and enhancing the efficiency of translation by ribosomes.

5 Must Know Facts For Your Next Test

1. The addition of the 3' poly-A tail occurs after transcription and is catalyzed by the enzyme polyadenylate polymerase.
2. The length of the poly-A tail can vary, typically ranging from 50 to 250 adenine residues, which influences mRNA stability and translational efficiency.
3. A shorter poly-A tail is often associated with decreased stability of the mRNA and may lead to its rapid degradation.
4. The poly-A tail plays a role in the initiation of translation, as it interacts with proteins that help recruit ribosomes to the mRNA.
5. Some viruses, particularly those with RNA genomes, can also utilize mechanisms similar to the poly-A tail for their own mRNA stability and translation enhancement.

Review Questions

• How does the presence of a 3' poly-A tail influence the stability and translation of mRNA?
  • The 3' poly-A tail significantly enhances the stability of mRNA by protecting it from degradation by exonucleases. A longer poly-A tail is associated with increased translation efficiency because it interacts with proteins that recruit ribosomes to initiate protein synthesis. Without a proper poly-A tail, mRNA may be more prone to degradation and less effective in directing protein production.
• Compare and contrast the functions of the 3' poly-A tail and the 5' cap in mRNA processing and stability.
  • Both the 3' poly-A tail and the 5' cap serve important roles in mRNA processing and stability. The 5' cap protects the mRNA from degradation, facilitates export from the nucleus, and is critical for translation initiation. In contrast, the 3' poly-A tail also enhances mRNA stability but primarily aids in efficient translation by interacting with ribosomal machinery. While both modifications contribute to overall mRNA integrity, they have distinct structural features and specific functions within the cell.
• Evaluate how variations in poly-A tail length could impact viral strategies for mRNA translation and stability.
  • Variations in poly-A tail length can significantly impact viral strategies as viruses often mimic host cell mechanisms to ensure their RNA is effectively translated. Viruses with shorter poly-A tails may face challenges in evading host defenses, leading to faster degradation. Conversely, those that adapt longer tails can enhance their own mRNA stability and translational efficiency, allowing for increased viral protein production. Understanding these variations helps elucidate how viruses exploit cellular processes for their replication and survival.

Related terms

mRNA (messenger RNA): A type of RNA that carries genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.

5' cap:

A modified guanine nucleotide added to the 5' end of eukaryotic mRNA, important for stability, export, and initiation of translation.

Translation:

The process by which ribosomes synthesize proteins using the genetic code carried by mRNA.