What Is Base Excision Repair?
Excision repair: It can repair a variety of DNA damage, including abasic spots formed by base shedding, pyrimidine dimers, base alkylation, and single-strand breaks. This system is based on the cooperation of several enzymes. First, the phosphodiester bond is opened at either end of the injury, and then the base or a segment of oligonucleotide is cut off. Ligase links it together. Different DNA damage requires different special endonucleases to recognize and cleave.
- Excision repair: It can repair a variety of DNA damage, including abasic spots formed by base shedding, pyrimidine dimers, base alkylation, and single-strand breaks. This system is based on the cooperation of several enzymes. First, the phosphodiester bond is opened at either end of the injury, and then the base or a segment of oligonucleotide is cut off. Ligase links it together. Different DNA damage requires different special endonucleases to recognize and cleave.
Excision repair classification
- There are two forms of excision repair: one is base excision repair, which removes specific types of damage or inappropriate bases from DNA under the action of DNA glycosylase. The other is Nucleotide excision repair (NER), which is a system that recognizes broad-spectrum DNA damage. These damages are removed by a multifunctional enzyme complex, resulting in a DNA polymerase and DNA linkage Gap repaired by enzymes.
- Base excision repair
The main process of excision repair
- (1) Nucleotide excision repair (NER)
- Mainly repairs DNA damage that affects the structure of regional chromosomes, including UV-induced purimidine dimers, chemical molecules or DNA adducts between proteins and DNA, or DNA and DNA Cross-link and so on. If these forms of damage are not ruled out in a timely manner, DNA polymerase will not be able to recognize and stay at the location of the damage. At this time, the cell will activate the cell cycle checkpoint to completely stop the cell cycle. It mainly includes genome-wide nucleotide excision repair and transcription-coupled nucleotide excision repair [1] .
- The general process is: damage recognition --- the protein complex binds to the damage site-the DNA strand is cut at a few bases upstream and downstream of the mismatch site (5 'upstream and 3' downstream). On-remove the oligonucleotide sequence between the two nicks [2] -DNA polymerase synthesizes new fragments to fill the gap-ligase links the newly synthesized fragments to the original DNA
- (2) Base-excision repair (BER)
- All cells have different types of glycoside hydrolases that can recognize damaged nucleic acid sites. It can specifically cut N--glycosidic bonds on damaged nucleotides to form purines or depyrimidines on the DNA strand. Sites, collectively referred to as AP sites.
- A class of DNA glycoside hydrolase generally corresponds to a specific type of damage. For example, uracil glycoside hydrolase specifically recognizes uracil formed by the spontaneous deamination of cytosine in DNA, but does not hydrolyze the uracil in RNA molecules. N--glycosidic bond. Once the AP site is generated in the DNA molecule, the AP endonuclease cuts the glycoside-phosphate bond of the damaged nucleotide, and removes the small piece of DNA including the AP site nucleotide. Polymerase I synthesizes new fragments, which are finally linked by DNA ligase into a new repaired DNA strand [3] .