6qtv

Structural highlights

Function

[COP1_ARATH] E3 ubiquitin-protein ligase that acts as a repressor of photomorphogenesis and as an activator of etiolation in darkness. E3 ubiquitin ligases accept ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Represses photomorphogenesis in darkness by mediating ubiquitination and subsequent proteasomal degradation of light-induced transcription factors such as HY5, HYH and LAF1. Down-regulates MYB21, probably via ubiquitination process. Light stimuli abrogate the repression of photomorphogenesis, possibly due to its localization to the cytoplasm. Could play a role in switching between skotomorphogenetic and photomorphogenetic pathways.^{[1] [2]} [HFR1_ARATH] Atypical bHLH transcription factor that regulates photomorphogenesis through modulation of phytochrome (e.g. PHYA) and cryptochrome signalings (Ref.4, PubMed:11090209, PubMed:10995393, PubMed:19482971). Suppresses the transcriptional regulation activity of PIF4 by forming non-DNA-binding heterodimer.^{[3] [4] [5] [6]}

References

1. ↑ Shin B, Choi G, Yi H, Yang S, Cho I, Kim J, Lee S, Paek NC, Kim JH, Song PS, Choi G. AtMYB21, a gene encoding a flower-specific transcription factor, is regulated by COP1. Plant J. 2002 Apr;30(1):23-32. PMID:11967090
2. ↑ Holm M, Ma LG, Qu LJ, Deng XW. Two interacting bZIP proteins are direct targets of COP1-mediated control of light-dependent gene expression in Arabidopsis. Genes Dev. 2002 May 15;16(10):1247-59. PMID:12023303 doi:http://dx.doi.org/10.1101/gad.969702
3. ↑ Fairchild CD, Schumaker MA, Quail PH. HFR1 encodes an atypical bHLH protein that acts in phytochrome A signal transduction. Genes Dev. 2000 Sep 15;14(18):2377-91. PMID:10995393
4. ↑ Soh MS, Kim YM, Han SJ, Song PS. REP1, a basic helix-loop-helix protein, is required for a branch pathway of phytochrome A signaling in arabidopsis. Plant Cell. 2000 Nov;12(11):2061-74. doi: 10.1105/tpc.12.11.2061. PMID:11090209 doi:http://dx.doi.org/10.1105/tpc.12.11.2061
5. ↑ Yang SW, Jang IC, Henriques R, Chua NH. FAR-RED ELONGATED HYPOCOTYL1 and FHY1-LIKE associate with the Arabidopsis transcription factors LAF1 and HFR1 to transmit phytochrome A signals for inhibition of hypocotyl elongation. Plant Cell. 2009 May;21(5):1341-59. doi: 10.1105/tpc.109.067215. Epub 2009 May, 29. PMID:19482971 doi:http://dx.doi.org/10.1105/tpc.109.067215
6. ↑ Soh MS, Kim YM, Han SJ, Song PS. REP1, a basic helix-loop-helix protein, is required for a branch pathway of phytochrome A signaling in arabidopsis. Plant Cell. 2000 Nov;12(11):2061-74. doi: 10.1105/tpc.12.11.2061. PMID:11090209 doi:http://dx.doi.org/10.1105/tpc.12.11.2061