THE SURVEILLANCE COMPLEX INTERACTS WITH THE TRANSLATION RELEASE FACTORS TO ENHANCE TERMINATION AND DEGRADE ABERRANT MESSENGER-RNAS

The nonsense-mediated mRNA decay pathway is an example of an evolution arily conserved surveillance pathway that rids the cell of transcripts that contain nonsense mutations. The product of the UPF1 gene is a ne cessary component of the putative surveillance complex that recognizes and degrades aberrant mRNAs. Recent results indicate that the Upf1p a lso enhances translation termination at a nonsense codon. The results presented here demonstrate that the yeast and human forms of the Upf1p interact with both eukaryotic translation termination factors eRF1 an d eRF3. Consistent with Upf1p interacting with the eRFs, the Upf1p is found in the prion-like aggregates that contain eRF1 and eRF3 observed in yeast [PSI+] strains. These results suggest that interaction of th e Upf1p with the peptidyl release factors may be a key event in the as sembly of the putative surveillance complex that enhances translation termination, monitors whether termination has occurred prematurely, an d promotes degradation of aberrant transcripts.