The molecular mechanism of mammalian NER. DNA is damaged and the damage is recognized either by stalled RNA polymerase and CSB (transcription-coupled repair, outer circle) or with the help of an accessory protein (global repair, inner pathway). The damaged DNA is excised in an approximately 26 base pair long oligodeoxynucleotide. The excised oligodeoxynucleotide is released in complex with repair proteins. The gap is filled in with repair synthesis and ligated. Reproduced from ref. 22 with permission from The American Society for Biochemistry and Molecular Biology, Copyright 2017.