Component of light signal transduction machinery. Involved in repression of photomorphogenesis in darkness (By similarity). Plays a role in DNA repair by forming with DDB2 the UV-damaged DNA-binding protein complex (UV-DDB) (By similarity). Protein modification; protein ubiquitination. Interacts with DDA1 (PubMed:24563205). Binds to KTN80.2/DWA3 (PubMed:21421380). Interacts with HTD1 (PubMed:25358503). Belongs to the DDB1 family.