Mutations in the MOF2/SUI1 gene affect both translation and nonsense-mediated mRNA decay

Recent studies have demonstrated that cells have evolved elaborate mechanis ms to rid themselves of aberrant proteins and transcripts, The nonsense-med iated mRNA decay pathway (NMD) is: an example of a pathway that eliminates aberrant mRNAs. In yeast, a transcript is recognized as aberrant and is rap idly degraded if a specific sequence, called the DSE, is present 3' of a pr emature termination codon, Results presented here show that strains harbori ng the mof2-1, mof4-1, mof5-1, and mof8-1 alleles, previously demonstrated to increase the efficiency of programmed -1 ribosomal frameshifting, decrea se the activity of the NMD: pathway. The effect of the mof2-1 allele on NMD was characterized in more detail, Previous results demonstrated that the w ild-type MOF2 gene is identical to the SUI1 gene. Studies on the mof2-1 all ele of the SUI1 gene indicate that in addition to its role in recognition o f the AUG codon during translation initiation and maintenance of the approp riate reading frame during translation elongation, the Mof2 protein plays a role in the NMD pathway. The Mof2/Sui1p is conserved throughout nature and the human homolog of the Mof2p/Sui1p functions in yeast cells to activate NMD. These results; suggest that factors involved in NMD are general modula tors that act in several aspects of translation and mRNA turnover.