Proteasome inhibitors and knockdown of SMG1 cause accumulation of Upf1 and Upf2 in human cells.

The ubiquitin-proteasome system (UPS) is one of the most promising anticancer drug targets of the century. However, the involved molecular mechanisms are still unclear. The nonsense-mediated mRNA decay (NMD) pathway is a highly conserved pathway which degrades nonsense mutation‑containing mRNA selectively and efficiently.