The 26S proteasome function and Hsp90 activity involved in the regulation of HsfA2 expression in response to oxidative stress.
Heat shock transcription factor A2 (HsfA2) is induced under environmental stress and regulates transcription of various defense-related genes. Thus HsfA2 plays an important role in induction of defenses against different types of environmental stress, but its mode of regulation remains unknown. To clarify the signal transduction pathway involved in the regulation of HsfA2 expression, we investigated the effect of MG132, a 26S proteasome inhibitor, or geldanamycin (GDA), a heat shock protein 90 (Hsp90) inhibitor, on the transcription of HsfA2 and its targets, Hsp18.1-CI and ascorbate peroxidase 2 (Apx2), in Arabidopsis T87 cells. The levels of transcripts were significantly increased by treatment with MG132 or GDA. Overexpression of a dexamethazone-inducible dominant-negative form of Hsp90.2 in Arabidopsis plants caused significant expression of HsfA2 and its target gene on treatment with the compound. Treatment with MG132 or GDA had no effect on intracellular levels of reactive oxygen species (ROS). Interestingly, the levels of polyubiquitinated proteins as well as the levels of HsfA2 transcript were rapidly increased under oxidative stress derived from treatment with H2O2 or methylviologen, while they were completely suppressed by pre-treatment with ascorbate, a scavenger of ROS, under oxidative stress. The present findings suggest that the inhibition of 26S proteasome function and/or Hsp90 activity is involved in the induction of HsfA2 expression in response to oxidative stress.
Nishizawa-Yokoi
Ayako
A
Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara, 631-8505 Japan.
Tainaka
Hitoshi
H
Yoshida
Eriko
E
Tamoi
Masahiro
M
Yabuta
Yukinori
Y
Shigeoka
Shigeru
S
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001205:Ascorbic Acid / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D057149:Ubiquitinated Proteins / Q000378:metabolism
D029681:Arabidopsis Proteins; D016227:Benzoquinones; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; C000620134:HSFA2 protein, Arabidopsis; D018841:HSP90 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D007976:Leupeptins; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D057149:Ubiquitinated Proteins; D006861:Hydrogen Peroxide; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D010269:Paraquat; D001205:Ascorbic Acid; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C001277:geldanamycin