The txl1+ gene from Schizosaccharomyces pombe encodes a new thioredoxin-like 1 protein that participates in the antioxidant defence against tert-butyl hydroperoxide

Abstract

Yeasts are equipped with several putative single-domain thioredoxins located in different subcellular compartments. However, additional proteins containing thioredoxin domains are also encoded by the yeast genomes as described for mammals and other eukaryotic organisms. We report here the characterization of the fission yeast orthologue thioredoxin-like 1 (txl1+), which has been previously identified in mammals. Similarly to the human protein, the fission yeast Txl1 is a two-domain protein comprising an N-terminal thioredoxin-like domain and a C-terminal domain of unknown function. Many other yeasts and fungi species contain homologues of txl1+; however, there is no evidence of txl1+ orthologues in either Saccharomyces cerevisiae or plants. Txl1 is found in both the nucleus and the cytoplasm of Schizosaccharomyces pombe cells and exhibits a strong reducing activity coupled to thioredoxin reductase. In humans, TXL1 expression is induced by glucose deprivation and overexpression of TXL1 confers resistance against this stress. In contrast, a Sz. pombe Δtxl1 mutant was not affected in the response against glucose starvation but the Δtxl1 mutant strain showed a clear hypersensitivity to alkyl hydroperoxide. The mRNA levels of txl1+ in a h20 strain did not change in response to any oxidative insult (hydrogen peroxide or alkyl hydroperoxide) and the overexpression of an integrated copy of the wild-type txl1+ gene did not confer a significant increased resistance against alkyl hydroperoxide. Overall, these results indicate that the Txl1 role in the cellular detoxification of alkyl hydroperoxide is exerted through a constitutive transcription of txl1+.