Biochemical and redox characterization of the Mediator complex and its associated transcription factor GeBPL, a GLABROUS1 enhancer binding protein
Biochem. J. 2015, 468:385-400
Shaikhali J, Davoine C, Brännström K, Rouhier N, Bygdell J, Björklund S, Wingsle G

The eukaryotic Mediator integrates regulatory signals from promoter-bound transcription factors and transmits them to RNA polymerase II machinery. Although redox signaling is important in adjusting plant metabolism and development, nothing is known about a possible redox regulation of Mediator. Here, using pull-down and yeast two-hybrid assays, we demonstrate the association of MED10a, MED28 and MED32 Mediator subunits with the GLABROUS1 enhancer binding protein-like (GeBPL), a plant-specific transcription factor that binds a promoter containing CryR2 element. All the corresponding recombinant proteins form various types of covalent oligomers linked by intermolecular disulfide bonds that are reduced in vitro by the thioredoxin and/or glutathione/glutaredoxin systems. The presence of MED10a, MED28 and MED32 subunits or changes of its redox state affect the DNA-binding capacity of GeBPL suggesting that redox-driven conformational changes might modulate its activity. Overall, these results advance our understanding of how redox signaling affects transcription and identify Mediator as a novel actor in redox signaling pathways, relaying or integrating redox changes in combination to specific transcription factors as GeBPL.
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