5’ cap
Definition
The 5' cap is a modified guanine nucleotide added to the 5' end of eukaryotic mRNA shortly after transcription initiation. It plays critical roles in mRNA stability, nuclear export, and translation initiation.
5 Must Know Facts For Your Next Test
- The 5' cap consists of a 7-methylguanosine molecule linked via a 5' to 5' triphosphate bridge.
- Capping occurs co-transcriptionally, meaning it happens while the mRNA is still being synthesized by RNA polymerase II.
- The 5' cap protects mRNA from degradation by exonucleases.
- It is essential for efficient ribosome binding during translation initiation.
- Involved in the regulation of nuclear export of mRNA to the cytoplasm.
Review Questions
- What are the primary functions of the 5' cap in mRNA processing?
- How does the addition of a 5' cap protect mRNA molecules?
- Why is the 5' cap important for translation initiation?
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Related terms
Poly-A Tail: A stretch of adenine nucleotides added to the 3' end of eukaryotic mRNAs that aids in stability and export.
RNA Splicing: The process by which introns are removed from pre-mRNA and exons are joined together.
Exonuclease: An enzyme that degrades nucleic acids from their ends, either from the 3’ or the 5’ direction.
