SMG7 is a core component of the nonsense-mediated mRNA decay (NMD) pathway, functioning as an adapter protein that recruits UPF1 to mRNA degradation sites. In NMD, SMG7 forms a functional complex with SMG5 that recognizes phosphorylated UPF1 through its 14-3-3-like domain 1, enabling access to mRNA degradation machinery. SMG7 operates through two mechanistic pathways: it facilitates exonucleolytic decay by linking UPF1 to the CCR4-NOT deadenylase complex 2, and enables endonucleolytic activity of SMG6 through a two-factor authentication model where SMG5-SMG7 presence is required for SMG6 activation 3. SMG7 targets not only aberrant mRNAs with premature stop codons but also 3%-10% of normal mRNAs, particularly those with 3'UTR introns, upstream open reading frames, and long 3'UTRs 4. Beyond NMD, SMG7 exhibits DNA damage response functions, playing a critical role in ATR-CHK1 axis activation by stabilizing the 9-1-1 checkpoint complex during genotoxic stress 5. Clinically, dysregulation of SMG7-AS1 (an associated long noncoding RNA) correlates with melanoma progression and immunotherapy response 6. SMG7 demonstrates functional redundancy with SMG5, with either protein sufficient to activate NMD 3.