5' cap
Definition
The 5' cap is a modified guanine nucleotide added to the 5' end of eukaryotic mRNA shortly after transcription initiation. It protects the mRNA from degradation and is critical for translation initiation.
5 Must Know Facts For Your Next Test
- The 5' cap is added to pre-mRNA during transcription by RNA polymerase II.
- It involves the addition of a methylated guanine (7-methylguanosine) at the 5' end of the mRNA.
- The cap structure is recognized by cap-binding proteins which facilitate ribosome binding for translation.
- Capping enhances mRNA stability by protecting it from exonucleases.
- The presence of a 5' cap is essential for efficient splicing, nuclear export, and translation of the mRNA.
Review Questions
- What specific modification occurs at the 5' end of eukaryotic mRNA?
- Why is the 5' cap important for mRNA stability?
- How does the 5' cap contribute to translation initiation?
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Related terms
Poly-A Tail: A stretch of adenine nucleotides added to the 3' end of eukaryotic mRNA that aids in stability and export from the nucleus.
Splicing: The process by which introns are removed from pre-mRNA and exons are joined together to form mature mRNA.
mRNA Export: The process through which mature mRNA is transported from the nucleus to the cytoplasm where it can be translated into protein.
