Caspases shutdown nonsense-mediated mRNA decay during apoptosis.

Nonsense-mediated mRNA decay (NMD) is an mRNA surveillance mechanism that plays integral roles in eliminating mRNAs with premature termination codons to prevent the synthesis of truncated proteins that could be pathogenic. One response to the accumulation of detrimental proteins is apoptosis, which involves the activation of enzymatic pathways leading to protein and nucleic acid cleavage and culminating in cell death. It is not clear whether NMD is required to ensure the accurate expression of apoptosis genes or is no longer necessary since cytotoxic proteins are not an issue during cell death. The present study shows that caspases cleave the two NMD factors UPF1 and UPF2 during apoptosis impairing NMD. Our results demonstrate a new regulatory pathway for NMD that occurs during apoptosis and provide evidence for role of the UPF cleaved fragments in apoptosis and NMD inhibition.