mRNA methylguanosine-cap decapping

Definition

Target type: biologicalprocess

Cleavage of the 5'-methylguanosine-cap of an mRNA. The methylguanosine-cap is present at the 5'-end of eukaryotic mRNAs. Decapping inactivates translation initiation and promotes 5'-to-3' decay of mRNA. [PMID:23287066]

mRNA decapping is a crucial step in the regulation of gene expression and mRNA turnover. It involves the removal of the 5'-methylguanosine (m7G) cap, a protective structure found at the 5' end of eukaryotic mRNAs. This process is carried out by a group of enzymes called decapping enzymes, which are highly conserved across species. The decapping process proceeds through a series of steps:

1. **Recognition and Binding:** Decapping enzymes recognize and bind to the m7G cap structure.
2. **Phosphorylation:** The m7G cap is first phosphorylated by a decapping enzyme, specifically a 5'-3' exoribonuclease. This phosphorylation step is critical for the subsequent removal of the cap.
3. **Hydrolysis:** The phosphorylated m7G cap is then hydrolyzed by the decapping enzyme, breaking the bond between the guanine base and the 5' phosphate of the mRNA molecule.
4. **Release:** The cleaved m7G cap is released, leaving the mRNA molecule with a free 5' phosphate.

Following decapping, the mRNA molecule becomes vulnerable to degradation by 5'-3' exoribonucleases, which can rapidly degrade the mRNA from the 5' end to the 3' end. This degradation process ensures that the mRNA molecule is no longer available for translation and is eventually eliminated from the cell.

The process of mRNA decapping plays a crucial role in various cellular processes, including:

* **Regulation of gene expression:** Decapping can regulate the lifespan of mRNAs, thereby controlling the levels of specific proteins produced by the cell.
* **mRNA turnover:** Decapping is a key step in the degradation pathway of mRNAs, ensuring the removal of damaged or unwanted mRNAs.
* **Translation initiation:** The m7G cap is essential for the recruitment of ribosomes to the mRNA molecule and the initiation of translation. Decapping removes this cap, inhibiting further translation.

Several factors can influence the decapping process, including:

* **mRNA sequence:** Certain mRNA sequences can promote or inhibit decapping.
* **Translational efficiency:** mRNAs that are actively translated are often protected from decapping.
* **Cellular environment:** Decapping activity can be influenced by factors such as stress, nutrient availability, and developmental stage.

The study of mRNA decapping provides valuable insights into the complex mechanisms that regulate gene expression and cellular processes. It also highlights the importance of this process in maintaining cellular homeostasis and responding to environmental changes.'
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Proteins (1)

Compounds (2)