What is the primary function of the polyA tail in eukaryotic mRNA?

What is the primary function of the polyA tail in eukaryotic mRNA?

• A. Stabilization of the mRNA
• B. Translation initiation
• C. Function is unknown
• D. Facilitation of splicing

Answer: (A)

The polyA tail primarily stabilizes mRNA. By adding a string of adenine nucleotides at the 3' end, the transcript becomes more resistant to exonucleases, which slows its degradation in the cytoplasm and lengthens how long the message can be used to make protein. This increased stability often translates to higher protein output because the mRNA remains available longer for translation. The tail also helps with efficient translation by binding poly(A)-binding protein, which fosters a close loop between the 3' end and the 5' cap through interactions with translation factors. This looping promotes translation efficiency and ribosome recycling, but the fundamental, primary effect remains the extended lifetime of the mRNA. Splicing occurs earlier in processing and is not driven by the polyA tail; the tail is added after transcription termination. The idea that its function is unknown is incorrect.

The polyA tail primarily stabilizes mRNA. By adding a string of adenine nucleotides at the 3' end, the transcript becomes more resistant to exonucleases, which slows its degradation in the cytoplasm and lengthens how long the message can be used to make protein. This increased stability often translates to higher protein output because the mRNA remains available longer for translation.

The tail also helps with efficient translation by binding poly(A)-binding protein, which fosters a close loop between the 3' end and the 5' cap through interactions with translation factors. This looping promotes translation efficiency and ribosome recycling, but the fundamental, primary effect remains the extended lifetime of the mRNA.

Splicing occurs earlier in processing and is not driven by the polyA tail; the tail is added after transcription termination. The idea that its function is unknown is incorrect.