title: APETALA1 and SEPALLATA3 interact with SEUSS to mediate transcription repression during flower development.
abstract: The transcriptional repression of key regulatory genes is crucial for plant and animal development. Previously, we identified and isolated two Arabidopsis transcription co-repressors LEUNIG (LUG) and SEUSS (SEU) that function together in a putative co-repressor complex to prevent ectopic AGAMOUS (AG) transcription in flowers. Because neither LUG nor SEU possesses a recognizable DNA-binding motif, how they are tethered to specific target promoters remains unknown. Using the yeast two-hybrid assay and a co-immunoprecipitation assay, we showed that APETALA1 (AP1) and SEPALLATA3 (SEP3), both MADS box DNA-binding proteins, interacted with SEU. The AP1-SEU protein-protein interaction was supported by synergistic genetic interactions between ap1 and seu mutations. The role of SEU proteins in bridging the interaction between AP1/SEP3 and LUG to repress target gene transcription was further demonstrated in yeast and plant cells, providing important mechanistic insights into co-repressor function in plants. Furthermore, a direct in vivo association of SEU proteins with the AG cis-regulatory element was shown by chromatin immunoprecipitation. Accordingly, a reporter gene driven by the AG cis-element was able to respond to AP1- and SEP3-mediated transcriptional repression in a transient plant cell system when supplied with SEU and LUG. These results suggest that AP1 and SEP3 may serve as the DNA-binding partners of SEU/LUG. Our demonstration of the direct physical interaction between SEU and the C-terminal domain of SEP3 and AP1 suggests that AP1 and SEP3 MADS box proteins may interact with positive, as well as negative, regulatory proteins via their C-terminal domains, to either stimulate or repress their regulatory targets.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
authors.forename: Vaniyambadi V
authors.initials: VV
authors.lastname: Sridhar
authors.forename: Anandkumar
authors.initials: A
authors.lastname: Surendrarao
authors.forename: Zhongchi
authors.initials: Z
authors.lastname: Liu
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D035264:Flowers / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C417768:LUG protein, Arabidopsis; D026161:MADS Domain Proteins; C121158:SEP3 protein, Arabidopsis; C445880:SEUSS protein, Arabidopsis; D014157:Transcription Factors