 DDB2, in its heterodimeric complex with DDB1, and further complexed with the ubiquitin ligase protein CUL4A and with PARP1 rapidly associates with UV-induced damage within chromatin, with half-maximum association completed in 40 seconds.The PARP1 protein, attached to both DDB1 and DDB2, then PARylates (creates a poly-ADP ribose chain) on DDB2 that attracts the DNA remodeling protein ALC1.Action of ALC1 relaxes the chromatin at the site of UV damage to DNA.