6qtu

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]} [BBX24_ARATH] Acts as negative regulator of seedling photomorphogenesis and light-regulated inhibition of hypocotyl elongation (PubMed:17605755, PubMed:18540109, PubMed:21685177). BBX24/STO and BBX25/STH function as transcriptional corepressors of HY5 activity, leading to the down-regulation of BBX22 expression. BBX24/STO acts additively with BBX25/STH during de-etiolation and the hypocotyl shade avoidance response (PubMed:23624715). Functions as negative regulator of photomorphogenic UV-B responses by interacting with both COP1 and HY5 (PubMed:22410790). May act as a transcription factor in the salt-stress response (PubMed:12909688).^{[3] [4] [5] [6] [7] [8]}

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. ↑ Nagaoka S, Takano T. Salt tolerance-related protein STO binds to a Myb transcription factor homologue and confers salt tolerance in Arabidopsis. J Exp Bot. 2003 Oct;54(391):2231-7. doi: 10.1093/jxb/erg241. Epub 2003 Aug 8. PMID:12909688 doi:http://dx.doi.org/10.1093/jxb/erg241
4. ↑ Indorf M, Cordero J, Neuhaus G, Rodriguez-Franco M. Salt tolerance (STO), a stress-related protein, has a major role in light signalling. Plant J. 2007 Aug;51(4):563-74. doi: 10.1111/j.1365-313X.2007.03162.x. Epub 2007 , Jul 2. PMID:17605755 doi:http://dx.doi.org/10.1111/j.1365-313X.2007.03162.x
5. ↑ Kumagai T, Ito S, Nakamichi N, Niwa Y, Murakami M, Yamashino T, Mizuno T. The common function of a novel subfamily of B-Box zinc finger proteins with reference to circadian-associated events in Arabidopsis thaliana. Biosci Biotechnol Biochem. 2008 Jun;72(6):1539-49. doi: 10.1271/bbb.80041. Epub, 2008 Jun 7. PMID:18540109 doi:http://dx.doi.org/10.1271/bbb.80041
6. ↑ Yan H, Marquardt K, Indorf M, Jutt D, Kircher S, Neuhaus G, Rodriguez-Franco M. Nuclear localization and interaction with COP1 are required for STO/BBX24 function during photomorphogenesis. Plant Physiol. 2011 Aug;156(4):1772-82. doi: 10.1104/pp.111.180208. Epub 2011 Jun, 17. PMID:21685177 doi:http://dx.doi.org/10.1104/pp.111.180208
7. ↑ Jiang L, Wang Y, Li QF, Bjorn LO, He JX, Li SS. Arabidopsis STO/BBX24 negatively regulates UV-B signaling by interacting with COP1 and repressing HY5 transcriptional activity. Cell Res. 2012 Jun;22(6):1046-57. doi: 10.1038/cr.2012.34. Epub 2012 Mar 13. PMID:22410790 doi:http://dx.doi.org/10.1038/cr.2012.34
8. ↑ Gangappa SN, Crocco CD, Johansson H, Datta S, Hettiarachchi C, Holm M, Botto JF. The Arabidopsis B-BOX protein BBX25 interacts with HY5, negatively regulating BBX22 expression to suppress seedling photomorphogenesis. Plant Cell. 2013 Apr;25(4):1243-57. doi: 10.1105/tpc.113.109751. Epub 2013 Apr, 26. PMID:23624715 doi:http://dx.doi.org/10.1105/tpc.113.109751