nucleotide excision repair pathway NER pathway Nucleotide Excision Repair PW:0000130 The nucleotide excision repair pathway is an important mechanism for the detection of helix-distorting base alterations. Unlike the base excision repair pathway that only removes the damaged bases, the NER pathway removes an entire lesion-containing segment. The single-strand gap thus introduced is filled in by DNA polymerase using the undamaged strand as a template. The pathway can be subdivided into two sub-pathways: transcription-coupled and global genome repair. They only differ in the lesion recognition step while the core repair component is shared. nucleotide-excision repair pathway single-strand DNA repair pathway