Factor involved in transcription-coupled nucleotide excision repair (TC-NER) in response to UV damage. TC-NER allows RNA polymerase II-blocking lesions to be rapidly removed from the transcribed strand of active genes. Acts by promoting stabilization of ERCC6 by recruiting deubiquitinating enzyme USP7 to TC-NER complexes, preventing UV-induced degradation of ERCC6 by the proteasome. Interacts with the elongating form of RNA polymerase II (RNA pol IIo) and facilitates its ubiquitination at UV damage sites, leading to promote RNA pol IIo backtracking to allow access to the nucleotide excision repair machinery. Not involved in processing oxidative damage. Interacts with the elongating form of RNA polymerase II (RNA pol IIo). Interacts with ERCC6, ERCC8 and USP7. Accumulates at UV DNA damage sites. Monoubiquitinated: ubiquitination does not increase in response to UV. The disease is caused by variants affecting the gene represented in this entry. Belongs to the UVSSA family. Extended N-terminus.