Damage-specific DNA binding protein 1 (DDB1): a protein with a wide range of functions.

Damage-specific DNA binding protein 1 (DDB1) is a multifunctional protein that was first isolated as a subunit of a heterodimeric complex that recognises the UV-induced DNA lesions in the nucleotide excision repair pathway. DDB1 and DDB2 form a complex that promotes the global genome repair (GG-NER), whereas DDB1 and Cockayne syndrome group A protein (CSA) form a complex that contributes to the transcription-coupled repair (TC-NER) pathway. DDB1 is also a component of an ubiquitin-E3 ligase complex and functions as substrate or adapter protein between Cullin 4A (Cul4A) and CUL4-associated factors (DCAFs) to target substrates for ubiquitination. CUL4-DDB1 E3-ligase complex regulates the selective proteolysis of key proteins in DNA repair, replication and transcription. In addition, DDB1 plays a role in transcriptional regulation of UV-induced genes. It is conceivable that DDB1 acts as a sensor of damage to maintain the balance between genome integrity and cell cycle progression. However, the temporal order between these two events remains to be established.