SMG6 is a central component of the nonsense-mediated mRNA decay (NMD) pathway that functions as both an RNA endonuclease and regulatory adapter protein. The protein exhibits endonucleolytic activity that cleaves single-stranded RNA substrates to initiate mRNA degradation 1. SMG6 interacts with the key NMD factor UPF1 through both phosphorylation-dependent and phosphorylation-independent mechanisms, with the latter involving a conserved short linear motif that binds to UPF1's cysteine/histidine-rich domain 23. This interaction is mutually exclusive with UPF2 binding to UPF1, suggesting distinct conformational states regulate NMD complex formation 2. SMG6 functions redundantly with SMG7 in targeting the same mRNA substrates, indicating overlapping roles in the endo- and exonucleolytic decay pathways 4. Beyond NMD, SMG6 also associates with telomerase through protein-RNA and protein-protein interactions, binding telomerase RNA with high affinity 5. Clinically, SMG6 variants show protective effects against temporal lobe epilepsy, with reduced SMG6 expression correlating with decreased seizure frequency 6. The protein also influences HIV-1 reactivation, negatively regulating viral gene expression through its interaction with UPF1 7.