title: Two interacting bZIP proteins are direct targets of COP1-mediated control of light-dependent gene expression in Arabidopsis.
abstract: Arabidopsis COP1 acts to repress photomorphogenesis in the absence of light. It was shown that in the dark, COP1 directly interacts with the bZIP transcription factor HY5, a positive regulator of photomorphogenesis, and promotes its proteasome-mediated degradation. Here we identify a novel bZIP protein HYH, as a new target of COP1. We identify a physical and genetic interaction between HYH and COP1 and show that this interaction results in dark-specific degradation of HYH. Genetic analysis indicates that HYH is predominantly involved in blue-light regulation of development and gene expression, and that the function of HYH in part overlaps with that of HY5. The accumulation of HYH protein, not the mRNA, is dependent on the presence of HY5. Our data suggest that HYH and HY5 can, respectively, act as heterodimers and homodimers, thus mediating light-regulated expression of overlapping as well as distinct target genes. We propose that COP1 mediates light control of gene expression through targeted degradation of multiple photomorphogenesis-promoting transcription factors in the nucleus.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA.
authors.forename: Magnus
authors.initials: M
authors.lastname: Holm
authors.forename: Li-Geng
authors.initials: LG
authors.lastname: Ma
authors.forename: Li-Jia
authors.initials: LJ
authors.lastname: Qu
authors.forename: Xing-Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology*; D018744:DNA, Plant / Q000378:metabolism; D004268:DNA-Binding Proteins; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D016350:Leucine Zippers / Q000502:physiology*; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D063245:Plant Development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D010944:Plants / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D019076:Transgenes; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; C457459:HYH protein, Arabidopsis; D010940:Plant Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases