Mtt1 is a Upf1-like helicase that interacts with the translation termination factors and whose overexpression can modulate termination efficiency

Translation termination is the final step that completes the synthesis of a polypeptide. Premature translation termination by introduction of a nonsen se mutation leads to the synthesis of a truncated protein. We report the id entification and characterization of the product of the MTT1 gene, a helica se belonging to the Upf1-like family of helicases that is involved in modul ating translation termination. MTT1 is homologous to UPF1, a factor previou sly shown to function in both mRNA turnover and translation termination. Ov erexpression of MTT1 induced a nonsense suppression phenotype in a wild-typ e yeast strain. Nonsense suppression is apparently not due to induction of [PSI+], even though cooverexpression of HSP104 alleviated the nonsense supp ression phenotype observed in cells overexpressing MTT1, suggesting a more direct role of Hsp104p in the translation termination process. The MTT1 gen e product was shown to interact with translation termination factors and is localized to polysomes. Taken together, these results indicate that at lea st two members of a family of RNA helicases modulate translation terminatio n efficiency in cells.