DNA‐binding and repressor function are prerequisites for the turnover of the tomato heat stress transcription factor HsfB1. (14th November 2016)

• Record Type: Journal Article
• Authors: Röth, Sascha; Mirus, Oliver; Bublak, Daniela; Scharf, Klaus‐Dieter; Schleiff, Enrico
• Is Part Of: Plant journal. Volume 89:Number 1(2017:Jan.)
• Page Start: 31
• Page End: 44
• Publication Date: 2016-11-14
• Subjects: K/RLFGV transcription factor family -- protein half‐life -- protein degradation -- chaperone function -- Hsp90 -- abiotic stress response -- Solanum lycopersicum -- Arabidopsis thaliana; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.13317
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: 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. Significance Statement: Transcription factor turnover is important in modulating gene transcription after developmental signals or environmental changes. Here we show that both the DNA‐binding and repressor activity of the tomato heat stress transcription factor HsfB1 mediate its efficient turnover. We suggest that other transcription factors of the R/KLFGV‐type might be regulated similarly.