Nucleotide excision repair

Definition

Nucleotide excision repair (NER) is a DNA repair mechanism that removes bulky lesions, such as thymine dimers and chemical adducts, from the DNA strand. It involves the recognition of damage, excision of the damaged strand segment, and synthesis of a new DNA strand to replace it.

5 Must Know Facts For Your Next Test

1. NER is critical for repairing UV-induced damage like thymine dimers.
2. The process involves key proteins such as UvrABC endonuclease in prokaryotes.
3. NER consists of several steps: damage recognition, local unwinding of DNA, incision on both sides of the lesion, removal of the oligonucleotide containing the lesion, and gap-filling by DNA polymerase followed by ligation.
4. Defects in NER can lead to diseases such as xeroderma pigmentosum (XP), which results in extreme sensitivity to sunlight and a higher risk of skin cancer.
5. There are two sub-pathways within NER: global genome NER (GG-NER) that scans the entire genome for damage and transcription-coupled NER (TC-NER) that specifically targets lesions obstructing transcription.

Review Questions

• What types of DNA damage does nucleotide excision repair typically address?
• Which key proteins are involved in the nucleotide excision repair process in prokaryotes?
• How does a defect in nucleotide excision repair impact human health?

Related terms

Base Excision Repair (BER): A DNA repair mechanism that corrects small base lesions not causing major distortions.

Mismatch Repair (MMR): A system for correcting errors introduced during DNA replication.

Xeroderma Pigmentosum (XP): A genetic disorder caused by defects in nucleotide excision repair leading to extreme sensitivity to UV light.