Thioredoxin Reductase-dependent Inhibition of MCB Cell Cycle Box Activity in Saccharomyces cerevisiae

• Published in: The Journal of biological chemistry Vol. 272; no. 27; pp. 17045 - 17054
• Main Authors: Machado, André K., Morgan, Brian A., Merrill, Gary F.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 04-07-1997; American Society for Biochemistry and Molecular Biology
• Subjects: Cell Cycle; DNA-Binding Proteins - metabolism; Fungal Proteins - antagonists & inhibitors; Fungal Proteins - metabolism; Gene Deletion; Genes, Reporter; Hydrogen Peroxide - metabolism; Mutation; Nuclear Receptor Subfamily 4, Group A, Member 2; Oxidation-Reduction; Periodicity; Protein Binding; RNA, Messenger - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Thioredoxin-Disulfide Reductase - genetics; Thioredoxin-Disulfide Reductase - metabolism; Thioredoxins - metabolism; Transcription Factors - antagonists & inhibitors; Transcription Factors - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.27.17045

Mlu1 cell cycle box (MCB) elements are found near the start site of yeast genes expressed at G1/S. Basal promoters dependent on the elements for upstream activating sequence activity are inactive in Δswi6 yeast. Yeast were screened for mutations that activated MCB reporter genes in the absence of Swi6. The mutations identified a single complementation group. Functional cloning revealed the mutations were alleles of theTRR1 gene encoding thioredoxin reductase. Although deletion of TRR1 activated MCB reporter genes, high copy expression did not suppress reporter gene activity. The trr1 mutations strongly (20-fold) stimulated MCB- and SCB (Swi4/Swi6 cell cycle box)-containing reporter genes, but also weakly (3-fold) stimulated reporter genes that lacked these elements. The trr1mutations did not affect the level or periodicity of three endogenous MCB gene mRNAs (TMP1, RNR1, andSWI4). Deletion of thioredoxin genes TRX1 andTRX2 recapitulated the stimulatory effect oftrr1 mutations on MCB reporter gene activity. Conditions expected to oxidize thioredoxin (exposure to H2O2) induced MCB gene expression, whereas conditions expected to conserve thioredoxin (exposure to hydroxyurea) inhibited MCB gene expression. The results suggest that thioredoxin oxidation contributes to MCB element activation and suggest a link between thioredoxin-oxidizing processes such as ribonucleotide reduction and cell cycle-specific gene transcription.