Repressor of photomorphogenesis in the light. Probably part of the COP1/SPA E3 ubiquitin-protein ligase complex. Interacts with COP1 and CO (PubMed:12887588, PubMed:16854975). Binds to CRY1 in response to blue light, this interaction prevents SPA1/COP1 complex formation and thus avoid COP1-dependent degradation of the transcription factor HY5 by the proteasome and promotes hypocotyl elongation (PubMed:21511871). Up-regulated by red, far-red and blue light. The protein kinase domain is predicted to be catalytically inactive. The DWD box is required for interaction with DDB1A (By similarity). Reduced hypocotyl elongation in blue light.