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HY5  -  transcription factor HY5

Arabidopsis thaliana

Synonyms: BZIP TRANSCRIPTION FACTOR HY5, ELONGATED HYPOCOTYL 5, F2I11.150, F2I11_150, REVERSAL OF THE DET PHENOTYPE 5, ...
 
 
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High impact information on HY5

  • COP1 interacts directly with HY5 in the nucleus to regulate its activity negatively [1].
  • HY5 is a bZIP transcription factor that binds directly to the promoters of light-inducible genes, promoting their expression and photomorphogenic development [1].
  • The SUB1 gene encodes a Ca2+-binding protein that suppresses light-dependent accumulation of the transcription factor HY5 [2].
  • The COP1-SPA1 interaction defines a critical step in phytochrome A-mediated regulation of HY5 activity [3].
  • The accumulation of HYH protein, not the mRNA, is dependent on the presence of HY5 [4].
 

Biological context of HY5

  • Here we show that overexpression of Arabidopsis SPA1 results in a hyperetiolation phenotype and reduced accumulation of HY5 and HFR1 [5].
  • 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 [4].
  • In vitro DNA binding studies suggested that HY5 can bind specifically to the G-box DNA sequences but not to any of the other LREs present in the light-responsive promoters examined [6].
  • Phosphorylation of HY5 by casein kinase II requires the beta subunit 2, but does not affect HY5's susceptibility to ubiquitination [7].
  • Nuclear localization of the HY5 protein strongly suggests that the HY5 gene modulates the signal transduction pathways under the HY5-related development by controlling expression of genes downstream of these pathways [8].
 

Anatomical context of HY5

  • These results, together with previous epistasis studies, support models in which light signals, once perceived by different photoreceptors, converge downstream and act through a common cascade(s) of regulatory steps, as defined by DET1, HY5, COP1, and likely others, to derepress photomorphogenic development [9].
 

Associations of HY5 with chemical compounds

  • HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana [10].
  • The Arabidopsis HY5 gene has been defined genetically as a positive regulator of photomorphogenesis and recently has been shown to encode a basic leucine zipper type of transcription factor [6].
  • The data also suggest that HY5 and HYH are important negative regulators of auxin signaling amplitude in embryogenesis and seedling development [11].
 

Physical interactions of HY5

  • 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 [4].
 

Regulatory relationships of HY5

  • Here, we show that COP1 negatively regulates HY5, a bZIP protein and a positive regulator of photomorphogenic development [12].
  • Moreover, we show that UVR8 regulates expression of the transcription factor HY5 specifically when the plant is exposed to UV-B [13].
 

Other interactions of HY5

  • Furthermore cytokinins are shown to increase levels of HY5 protein accumulation, suggesting that cytokinins may function by reducing HY5 degradation by COP1 (constitutively photomorphogenic 1) [10].
  • Among its substrates is the basic domain/leucine zipper (bZIP) transcription factor ELONGATED HYPOCOTYL5 (HY5), one of the key regulators of photomorphogenesis under all light qualities, including UV-B responses required for tolerance to this environmental threat [14].
  • Epistatic analyses with the long hypocotyl hy1, hy2, hy3, hy4, and hy5 mutations suggested that these three loci, similar to COP1 and COP9, act downstream of both phytochromes and a blue light receptor, and probably HY5 as well [15].
  • Together with our previous studies of CIP7 and HY5, our data suggest that COP1 interacts directly with and regulates multiple physiological targets, which in turn regulate distinct sets of light-regulated responses [16].
  • Thus, the COP1-SPA1 interaction defines a critical step in coordinating COP1-mediated ubiquitination and subsequent degradation of HY5 with PHYA signaling [3].
 

Analytical, diagnostic and therapeutic context of HY5

  • Molecular cloning of the HY5 gene using a T-DNA-tagged mutant has revealed that the gene encodes a protein with a bZIP motif, one of the motifs found in transcriptional regulators [8].
  • Using limited proteolysis in combination with mass spectrometry, circular dichroism, and nuclear magnetic resonance spectroscopy, we have deduced that the N-terminal 77 amino acids of HY5 form a premolten globular structure, while amino acids 78-110, which constitute the basic region (BR) of the protein, exist in a molten globule state [17].
  • Chromatin immunoprecipitation showed that UVR8 associates with chromatin in the HY5 promoter region, providing a mechanistic basis for its involvement in regulating transcription [13].

References

  1. Targeted destabilization of HY5 during light-regulated development of Arabidopsis. Osterlund, M.T., Hardtke, C.S., Wei, N., Deng, X.W. Nature (2000) [Pubmed]
  2. SUB1, an Arabidopsis Ca2+-binding protein involved in cryptochrome and phytochrome coaction. Guo, H., Mockler, T., Duong, H., Lin, C. Science (2001) [Pubmed]
  3. The COP1-SPA1 interaction defines a critical step in phytochrome A-mediated regulation of HY5 activity. Saijo, Y., Sullivan, J.A., Wang, H., Yang, J., Shen, Y., Rubio, V., Ma, L., Hoecker, U., Deng, X.W. Genes Dev. (2003) [Pubmed]
  4. Two interacting bZIP proteins are direct targets of COP1-mediated control of light-dependent gene expression in Arabidopsis. Holm, M., Ma, L.G., Qu, L.J., Deng, X.W. Genes Dev. (2002) [Pubmed]
  5. The central coiled-coil domain and carboxyl-terminal WD-repeat domain of Arabidopsis SPA1 are responsible for mediating repression of light signaling. Yang, J., Wang, H. Plant J. (2006) [Pubmed]
  6. Arabidopsis bZIP protein HY5 directly interacts with light-responsive promoters in mediating light control of gene expression. Chattopadhyay, S., Ang, L.H., Puente, P., Deng, X.W., Wei, N. Plant Cell (1998) [Pubmed]
  7. Biochemical evidence for ubiquitin ligase activity of the Arabidopsis COP1 interacting protein 8 (CIP8). Hardtke, C.S., Okamoto, H., Stoop-Myer, C., Deng, X.W. Plant J. (2002) [Pubmed]
  8. The Arabidopsis HY5 gene encodes a bZIP protein that regulates stimulus-induced development of root and hypocotyl. Oyama, T., Shimura, Y., Okada, K. Genes Dev. (1997) [Pubmed]
  9. Regulatory hierarchy of photomorphogenic loci: allele-specific and light-dependent interaction between the HY5 and COP1 loci. Ang, L.H., Deng, X.W. Plant Cell (1994) [Pubmed]
  10. HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana. Vandenbussche, F., Habricot, Y., Condiff, A.S., Maldiney, R., Straeten, D.V., Ahmad, M. Plant J. (2007) [Pubmed]
  11. Opposite Root Growth Phenotypes of hy5 versus hy5 hyh Mutants Correlate with Increased Constitutive Auxin Signaling. Sibout, R., Sukumar, P., Hettiarachchi, C., Holm, M., Muday, G.K., Hardtke, C.S. PLoS Genet. (2006) [Pubmed]
  12. Molecular interaction between COP1 and HY5 defines a regulatory switch for light control of Arabidopsis development. Ang, L.H., Chattopadhyay, S., Wei, N., Oyama, T., Okada, K., Batschauer, A., Deng, X.W. Mol. Cell (1998) [Pubmed]
  13. A UV-B-specific signaling component orchestrates plant UV protection. Brown, B.A., Cloix, C., Jiang, G.H., Kaiserli, E., Herzyk, P., Kliebenstein, D.J., Jenkins, G.I. Proc. Natl. Acad. Sci. U.S.A. (2005) [Pubmed]
  14. CONSTITUTIVELY PHOTOMORPHOGENIC1 is required for the UV-B response in Arabidopsis. Oravecz, A., Baumann, A., Máté, Z., Brzezinska, A., Molinier, J., Oakeley, E.J., Adám, E., Schäfer, E., Nagy, F., Ulm, R. Plant Cell (2006) [Pubmed]
  15. Arabidopsis COP8, COP10, and COP11 genes are involved in repression of photomorphogenic development in darkness. Wei, N., Kwok, S.F., von Arnim, A.G., Lee, A., McNellis, T.W., Piekos, B., Deng, X.W. Plant Cell (1994) [Pubmed]
  16. Cip4, a new COP1 target, is a nucleus-localized positive regulator of Arabidopsis photomorphogenesis. Yamamoto, Y.Y., Deng, X., Matsui, M. Plant Cell (2001) [Pubmed]
  17. Intrinsically unstructured N-terminal domain of bZIP transcription factor HY5. Yoon, M.K., Shin, J., Choi, G., Choi, B.S. Proteins (2006) [Pubmed]
 
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