title: Interactions between DNA, transcriptional regulator Dreb2a and the Med25 mediator subunit from Arabidopsis thaliana involve conformational changes.
abstract: Mediator is a multiprotein coregulatory complex that conveys signals from DNA-bound transcriptional regulators to the RNA polymerase II transcription machinery in eukaryotes. The molecular mechanisms for how these signals are transmitted are still elusive. By using purified transcription factor Dreb2a, mediator subunit Med25 from Arabidopsis thaliana, and a combination of biochemical and biophysical methods, we show that binding of Dreb2a to its canonical DNA sequence leads to an increase in secondary structure of the transcription factor. Similarly, interaction between the Dreb2a and Med25 in the absence of DNA results in conformational changes. However, the presence of the canonical Dreb2a DNA-binding site reduces the affinity between Dreb2a and Med25. We conclude that transcription regulation is facilitated by small but distinct changes in energetic and structural parameters of the involved proteins.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Blomberg
authors.forename: Ximena
authors.initials: X
authors.lastname: Aguilar
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Brännström
authors.forename: Linn
authors.initials: L
authors.lastname: Rautio
authors.forename: Anders
authors.initials: A
authors.lastname: Olofsson
authors.forename: Pernilla
authors.initials: P
authors.lastname: Wittung-Stafshede
authors.forename: Stefan
authors.initials: S
authors.lastname: Björklund
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D006801:Humans; D056892:Mediator Complex / Q000737:chemistry; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C114579:DREB2A protein, Arabidopsis; C483045:MED25 protein, human; D056892:Mediator Complex; D009687:Nuclear Proteins; C475686:PFT1 protein, Arabidopsis; D014157:Transcription Factors; D004247:DNA