page_title: MRNA surveillance
section_title: Nonsense-mediated mRNA decay
hierarchical_section_title: MRNA surveillance / Nonsense-mediated mRNA decay
caption_attribution_description: English: phosphorylation/dephosphorylation
context_page_description: mRNA surveillance mechanisms are pathways utilized by organisms to ensure fidelity and quality of messenger RNA molecules. There are a number of surveillance mechanisms present within cells. These mechanisms function at various steps of the mRNA biogenesis pathway to detect and degrade transcripts that have not properly been processed.
caption: UPF1 is a conserved helicase which is phosphorylated in the process of NMD. This phosphorylation is catalyzed by SMG1 kinase. This process requires UPF2 and UPF3. Dephosphorylation of UPF1 is catalyzed by SMG5, SMG6 and SMG7 proteins.[5]
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