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Basic steps of base excision repair. Base excision repair (BER) is a cellular mechanism, studied in the fields of biochemistry and genetics, that repairs damaged DNA throughout the cell cycle. It is responsible primarily for removing small, non-helix-distorting base lesions from the genome. The related nucleotide excision repair pathway repairs
Enzymes, namely DNA glycosylases, also commonly create AP sites, as part of the base excision repair pathway. In a given mammalian cell, 5000–10,000 apurinic sites are estimated to form per day. Apyrimidinic sites form at a rate roughly 20 times slower, with estimates at around 500 formation events per day, per cell.
Uracil-DNA glycosylases are DNA repair enzymes that excise uracil residues from DNA by cleaving the N-glycosydic bond, initiating the base excision repair pathway. Uracil in DNA can arise either through the deamination of cytosine to form mutagenic U:G mispairs, or through the incorporation of dUMP by DNA polymerase to form U:A pairs. [18]
Nucleotide excision repair is a DNA repair mechanism. [2] DNA damage occurs constantly because of chemicals (e.g. intercalating agents ), radiation and other mutagens . Three excision repair pathways exist to repair single stranded DNA damage: Nucleotide excision repair (NER), base excision repair (BER), and DNA mismatch repair (MMR).
Apurinic/apyrimidinic (AP) endonuclease is an enzyme that is involved in the DNA base excision repair pathway (BER). Its main role in the repair of damaged or mismatched nucleotides in DNA is to create a nick in the phosphodiester backbone of the AP site created when DNA glycosylase removes the damaged base.
AP sites are pre-mutagenic lesions that can prevent normal DNA replication. All cells, from simple prokaryotes to humans, have evolved systems to identify and repair such sites. Class II AP endonucleases cleave the phosphodiester backbone 5' to the AP site, thereby initiating a process known as base excision repair (BER). The APEX gene ...
It is involved in oxidative DNA damage repair and is part of the base excision repair pathway. The enzyme excises adenine bases from the DNA backbone at sites where adenine is inappropriately paired with guanine, cytosine, or 8-oxo-7,8-dihydroguanine, a common form of oxidative DNA damage.
One important function of uracil-DNA glycosylases is to prevent mutagenesis by eliminating uracil from DNA molecules by cleaving the N-glycosidic bond and initiating the base-excision repair (BER) pathway. Uracil bases occur from cytosine deamination or misincorporation of dUMP residues.