PT - JOURNAL ARTICLE AU - Volker Boehm AU - Sabrina Kueckelmann AU - Jennifer V. Gerbracht AU - Thiago Britto-Borges AU - Janine Altmüller AU - Christoph Dieterich AU - Niels H. Gehring TI - Nonsense-mediated mRNA decay relies on “two-factor authentication” by SMG5-SMG7 AID - 10.1101/2020.07.07.191437 DP - 2020 Jan 01 TA - bioRxiv PG - 2020.07.07.191437 4099 - http://biorxiv.org/content/early/2020/07/07/2020.07.07.191437.short 4100 - http://biorxiv.org/content/early/2020/07/07/2020.07.07.191437.full AB - Eukaryotic gene expression is constantly regulated and controlled by the translation-coupled nonsense-mediated mRNA decay (NMD) pathway. Aberrant translation termination leads to NMD activation and robust clearance of NMD targets via two seemingly independent and redundant mRNA degradation branches. Here, we uncover that the loss of the first SMG5-SMG7-dependent pathway also inactivates the second SMG6-dependent branch, indicating an unexpected functional hierarchy of the final NMD steps. Transcriptome-wide analyses of SMG5-SMG7-depleted cells confirm complete NMD inhibition resulting in massive transcriptomic alterations. The NMD activity conferred by SMG5-SMG7 is determined to varying degrees by their interaction with the central NMD factor UPF1, heterodimer formation and the initiation of deadenylation. Surprisingly, we find that SMG5 functionally substitutes SMG7 and vice versa. Our data support an improved model for NMD execution that requires two-factor authentication involving UPF1 phosphorylation and SMG5-SMG7 recruitment to access SMG6 activity.Competing Interest StatementThe authors have declared no competing interest.