Essential factor involved in transcription-coupled nucleotide excision repair (TCR) which allows RNA polymerase II-blocking lesions to be rapidly removed from the transcribed strand of active genes. Upon DNA-binding, it locally modifies DNA conformation by wrapping the DNA around itself, thereby modifying the interface between stalled RNA polymerase II and DNA. It is required for transcription-coupled repair complex formation. Homodimer. Binds DNA. Accumulates after genotoxic agents treatment such as bleomycin (BLM), a small peptide that create DNA double strand breaks (DSBs). Belongs to the SNF2/RAD54 helicase family.