Identification of a novel thioredoxin-1 pseudogene on human chromosome 10.

Abstract

Thioredoxin (Trx) is a small, ubiquitous protein of 12 kDa that acts as general dithiol-disulfide oxidoreductase via its conserved redox active site Trp-Cys-Gly-Pro-Cys which is located in a protrusion of the protein (Holmgren 1985). Mammalian cells contain two forms of thioredoxin: Trx1, a cytosolic enzyme able to translocate to the nucleus under certain stimuli and be secreted from the cells thus displaying cytokine-like properties and Trx2, a mitochondrial enzyme (Tagaya et al. 1989; Spyrou et al 1997). While many functions have been described for Trx1 for example antioxidant enzyme, modulator of transcription factors, electron donor for enzymes like ribonucleotide reductase and PAPS reductase, etc. (see introduction Spyrou et al. 1997), only an antioxidant function has been assigned to Trx2. Trx2 acts as a reductant of a mitochondrial thioredoxin-dependent peroxidase which protects cells against hydrogen peroxide treatment (Araki et al. 1999). Human Trx1 gene maps at chromosome 9q31 and several bands hybridize with a Trx1 probe in Southern blots suggesting the existence of Trx1 derived sequences in the human genome (Heppell-Parton et al. 1995; Kaghad et al. 1994). As only one active Trx1 gene has been described, the other hybridizing bands might correspond to different inactive pseudogenes (Kaghad et al. 1994), but only one Trx1 pseudogene has been described so far (GenBank accession number: AF146023 (Tonissen and Wells 1991)). We report here the sequence of a second Trx1 retrotranscribed pseudogene and propose the nomenclature wTrx1-1 and wTrx1-2.