title: A competitive peptide inhibitor KIDARI negatively regulates HFR1 by forming nonfunctional heterodimers in Arabidopsis photomorphogenesis.
abstract: 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-overexpressing 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.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul, Korea.
authors.forename: Shin-Young
authors.initials: SY
authors.lastname: Hong
authors.forename: Pil Joon
authors.initials: PJ
authors.lastname: Seo
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Ryu
authors.forename: Shin-Hae
authors.initials: SH
authors.lastname: Cho
authors.forename: Je-Chang
authors.initials: JC
authors.lastname: Woo
authors.forename: Chung-Mo
authors.initials: CM
authors.lastname: Park
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D019281:Dimerization; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D047468:Immunoprecipitation; D008027:Light; D009024:Morphogenesis / Q000502:physiology / Q000528:radiation effects; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D010834:Phytochrome; D015398:Signal Transduction; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010834:Phytochrome; C414438:At1g02340 protein, Arabidopsis; C513139:KIDARI protein, Arabidopsis; C459466:PIF4 protein, Arabidopsis