A competitive peptide inhibitor KIDARI negatively regulates HFR1 by forming nonfunctional heterodimers in Arabidopsis photomorphogenesis

• Published in: Molecules and cells Vol. 35; no. 1; pp. 25 - 31
• Main Authors: Hong, Shin-Young, Seo, Pil Joon, Ryu, Jae Yong, Cho, Shin-Hae, Woo, Je-Chang, Park, Chung-Mo
• Format: Journal Article
• Language: English
• Published: Springer Korean Society for Molecular and Cellular Biology 01-01-2013; Korea Society for Molecular and Cellular Biology
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Binding, Competitive; Biochemistry; Biomedical and Life Sciences; Biomedicine; Biotechnology; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Biology; Dimerization; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Gene Expression Regulation, Plant; Genetic Complementation Test; Hypocotyl - genetics; Hypocotyl - growth & development; Hypocotyl - metabolism; Immunoprecipitation; Life Sciences; Light; Morphogenesis - physiology; Morphogenesis - radiation effects; Mutation - genetics; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Peptide Fragments - genetics; Peptide Fragments - metabolism; Phytochrome; Research Article; Signal Transduction; Transcription, Genetic; Transcriptional Activation; Two-Hybrid System Techniques; light signaling; PHYTOCHROMEINTERACTING FACTOR (PIF); LONG HYPOCOTYL IN FAR-RED 1 (HFR1); competitive inhibition; KIDARI (KDR)
• ISSN: 1016-8478; 0219-1032
• DOI: 10.1007/s10059-013-2159-2

Dynamic dimer formation is an elaborate means of modulating transcription factor activities in diverse cellular processes. The basic helix-loop-helix (bHLH) transcription factor LONG HYPOCOTYL IN FAR-RED 1 (HFR1), for example, plays a role in plant photomorphogenesis by forming non-DNA binding heterodimers with PHYTOCHROMEINTERACTING FACTORS (PIFs). Recent studies have shown that a small HLH protein KIDARI (KDR) negatively regulates the HFR1 activity in the process. However, molecular mechanisms underlying the KDR control of the HFR1 activity are unknown. Here, we demonstrate that KDR attenuates the HFR1 activity by competitively forming nonfunctional heterodimers, causing liberation of PIF4 from the transcriptionally inactive HFR1-PIF4 complex. Accordingly, the photomorphogenic hypocotyl growth of the
HFR1
-overexpres-sing plants can be suppressed by KDR coexpression, as observed in the
HFR1
-deficient
hfr1-201
mutant. These results indicate that the PIF4 activity is modulated through a double layer of competitive inhibition by HFR1 and KDR, which could in turn ensure fine-tuning of the PIF4 activity under fluctuating light conditions.