3' polyadenylation

Definition

3' polyadenylation is the addition of a poly(A) tail, a stretch of adenine nucleotides, to the 3' end of a newly synthesized mRNA molecule. This process is crucial for mRNA stability, export from the nucleus, and translation efficiency. The presence of the poly(A) tail also influences mRNA degradation and plays a significant role in gene expression regulation.

5 Must Know Facts For Your Next Test

1. The poly(A) tail typically consists of 50 to 250 adenine residues and is added to mRNA after transcription, enhancing its stability in the cytoplasm.
2. 3' polyadenylation occurs via a process involving the recognition of a specific signal sequence on the pre-mRNA, which recruits enzymes that facilitate the addition of the poly(A) tail.
3. This modification not only protects mRNA from enzymatic degradation but also aids in the transport of mRNA from the nucleus to the cytoplasm, ensuring proper translation.
4. 3' polyadenylation is regulated by various factors including specific RNA-binding proteins that influence the efficiency and length of the poly(A) tail added.
5. Dysregulation of 3' polyadenylation can lead to various diseases, including cancer, by affecting gene expression and protein synthesis.

Review Questions

• How does 3' polyadenylation influence mRNA stability and translation efficiency?
  • 3' polyadenylation enhances mRNA stability by adding a protective poly(A) tail that prevents degradation by exonucleases. This modification also facilitates efficient translation by promoting the recruitment of ribosomes and translation factors. The longer the poly(A) tail, the more stable the mRNA tends to be, allowing for greater protein synthesis. Thus, 3' polyadenylation plays a vital role in determining both the longevity and translatability of mRNA in cells.
• Discuss the mechanisms involved in recognizing and executing 3' polyadenylation during mRNA processing.
  • The recognition of where to add the poly(A) tail involves specific sequence signals on the pre-mRNA, such as the AAUAAA hexamer found near the 3' end. Upon transcription termination, an enzyme complex assembles at this site, consisting of cleavage and polyadenylation specificity factor (CPSF) and other proteins. This complex cleaves the pre-mRNA at a designated site, followed by Poly(A) polymerase adding adenine nucleotides to form the tail. This multi-step process ensures precise and efficient addition of the poly(A) tail to mature mRNA.
• Evaluate the implications of altered 3' polyadenylation patterns in relation to cellular function and disease development.
  • Altered patterns of 3' polyadenylation can significantly impact cellular function by affecting gene expression profiles. For example, changes in polyadenylation can lead to variations in protein isoforms produced from a single gene, potentially resulting in dysfunctional proteins associated with diseases like cancer or neurological disorders. Furthermore, these changes may disrupt normal regulatory mechanisms, leading to increased stability of oncogenes or decreased stability of tumor suppressor genes. Understanding these alterations provides insights into disease mechanisms and highlights potential therapeutic targets for intervention.

Related terms

mRNA: Messenger RNA (mRNA) is a type of RNA that conveys genetic information from DNA to the ribosome, where proteins are synthesized.

Transcription: Transcription is the process by which genetic information from DNA is copied into RNA, forming the precursor to mRNA.

RNA splicing: RNA splicing is the process of removing introns from a pre-mRNA transcript and joining together the remaining exons to form mature mRNA.