title: DNA-binding and repressor function are prerequisites for the turnover of the tomato heat stress transcription factor HsfB1.
abstract: HsfB1 is a central regulator of heat stress (HS) response and functions dually as a transcriptional co-activator of HsfA1a and a general repressor in tomato. HsfB1 is efficiently synthesized during the onset of HS and rapidly removed in the course of attenuation during the recovery phase. Initial results point to a complex regime modulating HsfB1 abundance involving the molecular chaperone Hsp90. However, the molecular determinants affecting HsfB1 stability needed to be established. We provide experimental evidence that DNA-bound HsfB1 is efficiently targeted for degradation when active as a transcriptional repressor. Manipulation of the DNA-binding affinity by mutating the HsfB1 DNA-binding domain directly influences the stability of the transcription factor. During HS, HsfB1 is stabilized, probably due to co-activator complex formation with HsfA1a. The process of HsfB1 degradation involves nuclear localized Hsp90. The molecular determinants of HsfB1 turnover identified in here are so far seemingly unique. A mutational switch of the R/KLFGV repressor motif's arginine and lysine implies that the abundance of other R/KLFGV type Hsfs, if not other transcription factors as well, might be modulated by a comparable mechanism. Thus, we propose a versatile mechanism for strict abundance control of the stress-induced transcription factor HsfB1 for the recovery phase, and this mechanism constitutes a form of transcription factor removal from promoters by degradation inside the nucleus.
authors: Molecular Cell Biology of Plants, Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.
authors: Sascha
authors: S
authors: Röth
authors: Molecular Cell Biology of Plants, Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.
authors: Oliver
authors: O
authors: Mirus
authors: Molecular Cell Biology of Plants, Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.
authors: Daniela
authors: D
authors: Bublak
authors: Molecular Cell Biology of Plants, Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.
authors: Klaus-Dieter
authors: KD
authors: Scharf
authors: Molecular Cell Biology of Plants, Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.|Cluster of Excellence 'Macromolecular Complexes', Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.|Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt/Main, Max-von-Laue Str. 9, Frankfurt/Main, Germany.
authors: Enrico
authors: E
authors: Schleiff
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D000076249:Heat Shock Transcription Factors / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics; D018551:Solanum lycopersicum / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011523:Protoplasts / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; C000620135:HSFB1 protein, Arabidopsis; D018841:HSP90 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D010940:Plant Proteins; D014157:Transcription Factors
keywords: 
  Arabidopsis thaliana
  ; 
  Solanum lycopersicum
  ; Hsp90; K/RLFGV transcription factor family; abiotic stress response; chaperone function; protein degradation; protein half-life