Nucleotide excision repair

Definition

Nucleotide excision repair is a DNA repair mechanism that removes bulky DNA lesions, such as those caused by ultraviolet (UV) light and certain chemical agents. This process involves the recognition of damaged DNA, excision of the damaged section, and subsequent resynthesis of the missing DNA using the complementary strand as a template. It is crucial for maintaining genomic integrity and preventing mutations that could lead to diseases like cancer.

5 Must Know Facts For Your Next Test

1. Nucleotide excision repair can recognize and repair a variety of DNA damage types, including thymine dimers formed by UV radiation.
2. The process involves several key proteins, including UV-damaged DNA-binding protein (UVD), excinuclease, and DNA polymerase.
3. In humans, defects in nucleotide excision repair are associated with conditions like xeroderma pigmentosum, where individuals have extreme sensitivity to UV light.
4. This repair pathway is evolutionarily conserved across many organisms, highlighting its importance in cellular maintenance.
5. Nucleotide excision repair is critical not only for repairing UV-induced damage but also for correcting lesions from environmental agents such as chemicals and oxidative stress.

Review Questions

• How does nucleotide excision repair differ from other DNA repair mechanisms like base excision repair?
  • Nucleotide excision repair differs from base excision repair primarily in the type of damage it addresses. While nucleotide excision repair targets bulky DNA adducts or lesions caused by UV light and chemicals, base excision repair focuses on small, non-bulky modifications such as altered bases. This distinction highlights the specificity of each repair mechanism in addressing different types of DNA damage.
• What role do specific proteins play in the nucleotide excision repair process, and how do they interact during the mechanism?
  • Specific proteins are crucial for the nucleotide excision repair process. Proteins like UVD recognize and bind to damaged sites, while excinuclease makes incisions around the lesion. Following this, DNA polymerase synthesizes new DNA to fill in the gap created by the excised segment. This coordinated action ensures accurate removal of damage and effective restoration of the DNA sequence.
• Evaluate the implications of defective nucleotide excision repair on human health and disease susceptibility.
  • Defective nucleotide excision repair can have serious implications for human health, particularly increasing susceptibility to cancers. Conditions such as xeroderma pigmentosum illustrate how impaired ability to repair UV-induced damage leads to high rates of skin cancer. Moreover, these defects can result in genomic instability and contribute to other diseases, underscoring the importance of this mechanism in protecting cellular integrity against environmental threats.

Related terms

DNA polymerase: An enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand during DNA replication and repair.

Base excision repair: A DNA repair mechanism that specifically removes and replaces damaged or non-canonical bases in the DNA, differing from nucleotide excision repair by targeting smaller, non-bulky lesions.

Homologous recombination: A repair process that fixes double-strand breaks in DNA by using a homologous sequence as a template, playing a critical role in maintaining genetic stability.