The DOT5 gene was originally cloned as one of the DOT (disrupter of telomeric silencing) genes; and later it was re-discovered as a nuclear thioredoxin peroxidase in Saccharomyces cerevisiae. Here, we demonstrate that the telomeric-silencing disruption activity of Dots is independent of thioredoxin peroxidase activity. In addition, Dots cannot suppress the increased susceptibility to peroxides of mutants defected in cytosolic thioredoxin peroxidase, even when Dots is expressed in the cytoplasm. Furthermore, Dots does not affect redox regulation of the Yap1 transcription factor. These results suggest that Dots is less important as an antioxidant in yeast cells.