E3 ubiquitin-protein ligase involved in postreplication repair of UV-damaged DNA. Postreplication repair functions in gap-filling of a daughter strand on replication of damaged DNA. Associates to the E2 ubiquitin conjugating enzyme UBE2B to form the UBE2B-RAD18 ubiquitin ligase complex involved in mono-ubiquitination of DNA-associated PCNA on 'Lys-164'. Has ssDNA binding activity.
Subcellular locations: Nucleus, Cytoplasm, Cytoskeleton, Microtubule organizing center, Centrosome
Associates with chromatin . Colocalizes with SLF1 in the nucleus and to centrosomes . Relocalizes with SLF1 to nuclear foci in response to DNA damage . Accumulates with the SLF1-SLF2 and SMC5-SMC6 complexes at replication-coupled DNA interstrand repair and DNA double-strand breaks (DSBs) sites on chromatin in a ubiquitin-dependent manner .