SMG1
SMG1 is the PIKK-family kinase that drives nonsense-mediated mRNA decay (NMD), the surveillance pathway that eliminates transcripts containing premature termination codons. Together with its regulators SMG8 and SMG9 it forms the SURF complex at terminating ribosomes and phosphorylates UPF1 on multiple Ser/Thr-Gln sites, a modification that licenses UPF1-dependent mRNA degradation and translational repression. SMG1 has additionally been reported to contribute to genome-stability control under oxidative stress. Compared with its DNA-damage relatives ATM and ATR, SMG1 is dedicated to RNA quality control rather than repair signaling. Recombinant SMG1 supports NMD reconstitution and UPF1 phosphorylation assays.
