 CRL4A complexes appear to be activated by certain types of DNA damage (most notably, UV-irradiation) and several substrates are preferentially ubiquitinated after DNA damage induction.CUL4A's role in modifying chromatin is largely related to DNA repair activities and occurs after DNA damage induction.Both CUL4A and its closely related homolog CUL4B may ubiquitinate histones H2A, H3 and H4.