nucleotide excision repair
NER operates by: (a) recognition of the damaged DNA; (b) excision of an oligonucleotide of 24–32 residues by dual incision of the damaged strand on each side of the lesion; and, as for BER (c) filling in of the resulting gap by DNA polymerase; and (d) ligation of the nick. There is evidence that at least some steps of NER require ATP-dependent chromatin remodeling activities.
NER can operate by two pathways. The first pathway, global genome repair (GGR), acts on DNA lesions across the genome and is transcription-independent. The second NER pathway, transcription coupled repair, is coupled to active transcription and is directed to the transcribed strand of active genes.
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