Mutations in SUP35 gene coding for translation termination factor eRF3 lead to NMD defect.
Svetlana Chabelskaya (1), Michel Philippe (2), Galina Zhouravleva (1)
(1) Department of Genetics and Breeding, St Petersburg State University, Universitetskaya emb. , 7/9, 199034, St Petersburg, Russia, Université de Rennes 1, CNRS UMR 6061, IFR 140, 2 av. Pr. Léon Bernard 35043 Rennes Cedex, France; (2) Université de Rennes 1, CNRS UMR 6061, IFR 140, 2 av. Pr. Léon Bernard 35043 Rennes Cedex, France
The nonsense-mediated mRNA decay (NMD) pathway promotes the rapid degradation of mRNAs containing premature termination codons (PTCs). In yeast Saccharomyces cerevisiae, the activity of the NMD pathway depends on the recognition of the PTC by the translational machinery. Two translation termination factors, eRF1 and eRF3, participate in termination of protein synthesis in eukaryotes. eRF1 recognizes all three stop codons ( UAG, UAA, and UGA ) and eRF3 forms a complex with eRF1 and stimulates termination through a GTP-dependent mechanism. In S. cerevisiae eRF1 and eRF3 are encoded by essential genes SUP45 and SUP35, respectively. Mutations in these genes cause a general decrease in the efficiency of translation termination and lead to suppression of nonsense-codons. To characterize the relationship between translation termination and NMD, we have we have studied steady-state levels of some mRNA, containing PTCs, in strains harboring mutations in SUP35 gene. We showed that suppressor mutations in SUP35 promote accumulation of aberrant mRNA harboring PTC and have an inhibitory effect on NMD. This was the case for sup35 nonsense-mutations leading to decrease amount of full-length translation termination factors eRF1 or eRF3 as well as for missense mutations. Our results support existence of a direct link between the termination complex and the mRNA stability and demonstrate that eRF3 protein is required for NMD. The work was supported by RFBR 03-04-48886 and to S.C. from FEBS.