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Cellular functions and transcriptional regulation of a third thioredoxin from Schizosaccharomyces pombe

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Abstract:

The structural gene encoding a third thioredoxin (Trx) homologue, TRX3, of the fission yeast Schizosaccharomyces pombe was characterized and its regulation was studied. The determined DNA sequence encoded a putative 290 amino acid sequence of Trx with a molecular mass of 31889Da. The TRX3 mRNA level was increased in S. pombe cells harboring plasmid pTRX3, suggesting that the cloned TRX3 gene was functional. Yeast cultures harbouring plasmid pTRX3 exhibited shorter generation times and higher survival on solid minimal media plates incorporating mercury chloride (0.01mmol/L) or hydrogen peroxide (1mmol/L) compared with control cultures. Yeast cells containing extra copies of TRX3, but not TRX1 and TRX2, gave rise to lower reactive oxygen species levels than control cells. Oxidative stress owing to hydrogen peroxide and menadione enhanced the synthesis of -galactosidase from the TRX3lacZ fusion gene in Pap1-positive cells but not in Pap1-negative cells. The TRX3 mRNA level was increased by oxidative stress only in Pap1-positive cells. Basal expression of the TRX3 gene also depended on Pap1. We concluded that S. pombe TRX3 is linked with yeast growth and oxidative stress response, with its expression being regulated by oxidative stress in a Pap1-dependent manner.

Le gène structurel codant le troisième homologue de la thiorédoxine (Trx), TRX3, de la levure à fission Schizosaccharomyces pombe, a été caractérisé et sa régulation a été étudiée. La séquence déterminée d’ADN code les 290 acides aminés de la séquence potentielle de TRX3 dont la masse moléculaire est de 31889Da. La quantité d’ARNm de TRX3 était augmentée chez S. pombe possédant le plasmide pTRX3, suggérant que le gène TRX3 cloné est fonctionnel. La culture de levures contenant le plasmide pTRX3 montrait un temps de génération plus court et un taux de survie plus élevé sur milieu minimal contenant du chlorure de mercure (0,01mmol/L) ou du peroxyde d’hydrogène (1mmol/L), comparativement à la culture contrôle. Les levures contenant des copies supplémentaires de TRX3, mais non TRX1 et TRX2, génèraient moins d’espèces réactives d’oxygène (ROS) que les cellules contrôles. Le stress oxydatif, tel que le peroxyde d’hydrogène et la ménadione, augmentait la synthèse de -galactosidase à partir d’un gène de fusion TRX3–lacZ chez les cellules exprimant Pap1, mais pas chez les cellules négatives. La quantité d’ARNm de TRX3 était augmentée par le stress oxydatif chez les cellules exprimant Pap1 seulement. L’expression de base du gène TRX3 dépendait aussi de Pap1. En somme, TRX3 est lié à la croissance et à la réponse oxydative chez la levure S.pombe, et son expression est régulée par le stress oxydatif de façon dépendante de Pap1.

Document Type: Research Article

Publication date: 2007-06-01

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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