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Quinone reductase acts as a redox switch of the 20 S yeast proteasome
Author(s) -
Sollner Sonja,
Schober Markus,
Wagner Andrea,
Prem Anna,
Lorkova Lucie,
Palfey Bruce A,
Groll Michael,
Macheroux Peter
Publication year - 2009
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1038/embor.2008.218
Subject(s) - proteasome , reductase , biochemistry , quinone , transcription factor , cofactor , flavin mononucleotide , chemistry , biology , microbiology and biotechnology , enzyme , gene
The proteasome has an essential function in the intracellular degradation of protein in eukaryotic cells. We found that the dimeric quinone reductase Lot6 uses the flavin mononucleotide (FMN)‐binding site to bind to the 20 S proteasome with a 1:2 stoichiometry—that is, one 20 S proteasome molecule can associate with two quinone reductases. Furthermore, reduction of the FMN cofactor by either NADH or light irradiation results in the binding of the b‐Zip transcription factor Yap4 to the Lot6–proteasome complex, indicating that recruitment of the transcription factor depends on the redox state of the quinone reductase. Here, we show that binding of Yap4 to the complex not only protects it from ubiquitin‐independent proteasomal degradation, but also regulates its cellular localization. In non‐stressed wild‐type cells, we did not detect any Yap4 in the nucleus, whereas Yap4 was present in the nuclei from quinone‐stressed yeast cultures. Thus, the Lot6–proteasome complex can be regarded as a redox switch in which the quinone reductase acts as a sensor for oxidative stress.