Nucleotide excision repair

Definition

Nucleotide excision repair (NER) is a DNA repair mechanism that removes bulky, helix-distorting lesions such as thymine dimers. It involves the recognition of damage, excision of a short single-stranded DNA segment containing the lesion, and synthesis of a new strand using the undamaged strand as a template.

5 Must Know Facts For Your Next Test

1. NER is crucial for repairing UV-induced damage like thymine dimers.
2. The process involves multiple steps: damage recognition, dual incision, removal of the damaged DNA segment, DNA synthesis, and ligation.
3. Two pathways of NER exist: global genomic NER (GG-NER) and transcription-coupled NER (TC-NER).
4. Key proteins involved include XPC for damage recognition in GG-NER and CSA/CSB for TC-NER.
5. Defects in NER can lead to genetic disorders such as Xeroderma Pigmentosum (XP), which increases sensitivity to UV radiation.

Review Questions

• What types of DNA damage are typically repaired by nucleotide excision repair?
• Describe the main steps involved in the nucleotide excision repair process.
• What are the differences between global genomic NER and transcription-coupled NER?

Related terms

Base Excision Repair (BER): A DNA repair mechanism that fixes small, non-helix-distorting base lesions.

Mismatch Repair (MMR): A system for correcting errors that escape proofreading during DNA replication.

Thymine Dimers: Covalent linkages between adjacent thymine bases in DNA caused by UV light exposure.