Dna glycosylase

Definition

DNA glycosylase is an enzyme responsible for recognizing and removing damaged or inappropriate bases from DNA. This process is crucial in the base excision repair pathway, which maintains the integrity of the genetic material by fixing mutations that can arise from environmental factors or normal cellular processes.

5 Must Know Facts For Your Next Test

1. DNA glycosylases play a pivotal role in recognizing specific types of damage, such as oxidized bases or deaminated bases, ensuring the repair process starts promptly.
2. These enzymes work by cleaving the N-glycosidic bond between the damaged base and the sugar-phosphate backbone, leaving behind an apurinic or apyrimidinic site.
3. Different types of DNA glycosylases exist for various types of lesions, such as uracil-DNA glycosylase for uracil and 8-oxoguanine-DNA glycosylase for oxidized guanine.
4. After the removal of a damaged base, other enzymes, including AP endonuclease and DNA polymerase, are recruited to complete the repair process by filling in the gap left behind.
5. Mutations in genes encoding DNA glycosylases can lead to increased susceptibility to cancer due to the accumulation of uncorrected DNA damage.

Review Questions

• How does DNA glycosylase contribute to the base excision repair mechanism?
  • DNA glycosylase initiates the base excision repair mechanism by identifying and removing damaged bases from the DNA strand. Once it recognizes a lesion, it breaks the bond between the base and the sugar-phosphate backbone, resulting in an apurinic site. This action sets off a cascade of repair processes where other enzymes come in to replace the missing nucleotide and restore the integrity of the DNA.
• What types of DNA damage are specifically targeted by different DNA glycosylases, and how does this specificity impact repair pathways?
  • Different DNA glycosylases are specialized for particular types of damage, such as uracil-DNA glycosylase targeting uracil in DNA and 8-oxoguanine-DNA glycosylase targeting oxidized guanine. This specificity ensures that each type of lesion is addressed appropriately, preventing misrepair or incomplete repairs that could lead to mutations. The effectiveness of these enzymes directly impacts the overall fidelity of the DNA repair process and cellular health.
• Evaluate the consequences of defective DNA glycosylase activity on genomic stability and cancer development.
  • Defective activity or mutations in DNA glycosylase can lead to impaired recognition and repair of damaged bases. This malfunction results in an accumulation of mutations within the genome, significantly compromising genomic stability. Over time, these uncorrected errors can promote tumorigenesis as cells acquire additional mutations that drive cancer progression. Thus, functional DNA glycosylases are essential for safeguarding against cancer by maintaining the fidelity of genetic information.

Related terms

Base Excision Repair: A cellular mechanism that repairs damaged DNA by removing and replacing incorrect or damaged bases, utilizing enzymes like DNA glycosylases.

Apurinic Site: A site in DNA that has lost a purine base, created during the action of DNA glycosylases, which must be further repaired to restore DNA integrity.

DNA Polymerase: An enzyme involved in DNA replication and repair that synthesizes new DNA strands by adding nucleotides to a pre-existing chain, often acting after DNA glycosylases have removed damaged bases.