The COP1 (constitutive photomorphogenic 1) protein, comprising RING finger, coiled-coil and WD40 domains, is conserved in both higher plants and vertebrates.
In plants, COP1 acts as an E3 ubiquitin ligase to repress light signaling by targeting photoreceptors and downstream transcription factors for ubiquitylation and degradation.
Mammalian COP1 has possible roles in tumorigenesis and the stress response through regulating the activities of p53 and c-Jun.
References
Yi C, Deng XW. COP1 - from plant photomorphogenesis to mammalian tumorigenesis. Trends Cell Biol. 2005 Nov;15(11):618-25. PMID: 16198569