key term - Poly(A) polymerase

Definition

Poly(A) polymerase is an enzyme responsible for adding a polyadenylate (poly(A)) tail to the 3' end of eukaryotic mRNA molecules during transcription. This modification is crucial for mRNA stability, export from the nucleus, and efficient translation. By facilitating these processes, Poly(A) polymerase plays a significant role in gene expression regulation.

5 Must Know Facts For Your Next Test

1. Poly(A) polymerase adds approximately 100-200 adenine nucleotides to the 3' end of eukaryotic mRNA, forming the poly(A) tail.
2. The poly(A) tail enhances mRNA stability by protecting it from degradation by exonucleases in the cytoplasm.
3. Polyadenylation is coupled with transcription termination and occurs shortly after the RNA polymerase synthesizes the pre-mRNA.
4. The length of the poly(A) tail can affect translation efficiency; longer tails generally lead to increased translation rates.
5. In addition to its role in mRNA processing, Poly(A) polymerase is involved in regulating gene expression through its influence on mRNA lifespan.

Review Questions

• How does Poly(A) polymerase contribute to the stability and functionality of eukaryotic mRNA?
  • Poly(A) polymerase contributes to mRNA stability by adding a poly(A) tail at the 3' end of the molecule, which protects it from enzymatic degradation. This modification not only enhances the lifespan of the mRNA in the cytoplasm but also plays a key role in facilitating mRNA export from the nucleus and promoting efficient translation. The presence of a poly(A) tail helps ribosomes recognize and bind to the mRNA, ensuring successful protein synthesis.
• Discuss how Poly(A) polymerase interacts with other transcriptional processes during gene expression.
  • Poly(A) polymerase interacts closely with transcriptional processes by being involved in both transcription termination and mRNA processing. As RNA polymerase transcribes DNA into pre-mRNA, Poly(A) polymerase recognizes specific signals that trigger polyadenylation. This process occurs right after transcription termination and is essential for producing mature mRNA. By coupling polyadenylation with transcription, it ensures that only properly processed RNA molecules are stabilized and translated, which is crucial for gene expression regulation.
• Evaluate the implications of altered Poly(A) polymerase activity on cellular function and gene regulation.
  • Altered Poly(A) polymerase activity can significantly impact cellular function and gene regulation by affecting mRNA stability and translation efficiency. If Poly(A) polymerase is overactive, it may lead to abnormally long poly(A) tails, potentially causing increased levels of certain proteins that could disrupt cellular homeostasis. Conversely, reduced activity could result in shorter tails and decreased mRNA stability, leading to lower protein production. These changes can contribute to various diseases, including cancer, where gene expression profiles are often altered.

Related terms

mRNA:

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

Transcription: Transcription is the process by which the genetic information in DNA is copied into RNA, forming the precursor to messenger RNA (pre-mRNA).

Capping: Capping refers to the addition of a modified guanine nucleotide at the 5' end of mRNA, which protects the RNA from degradation and assists in ribosome recognition.