DNA glycosylases are a family of enzymes involved in base excision repair, classified under EC number EC 3.2.2. Base excision repair is the mechanism by which damaged bases in DNA are removed and replaced. DNA glycosylases catalyze the first step of this process. They remove the damaged nitrogenous base while leaving the sugar-phosphate backbone intact, creating an apurinic/apyrimidinic site, commonly referred to as an AP site. This is accomplished by flipping the damaged base out of the double helix followed by cleavage of the N-glycosidic bond.
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 bulky helix-distorting lesions. BER is important for removing damaged bases that could otherwise cause mutations by mispairing or lead to breaks in DNA during replication. BER is initiated by DNA glycosylases, which recognize and remove specific damaged or inappropriate bases, forming AP sites. These are then cleaved by an AP endonuclease. The resulting single-strand break can then be processed by either short-patch or long-patch BER.
Werner syndrome ATP-dependent helicase, also known as DNA helicase, RecQ-like type 3, is an enzyme that in humans is encoded by the WRN gene. WRN is a member of the RecQ Helicase family. Helicase enzymes generally unwind and separate double-stranded DNA. These activities are necessary before DNA can be copied in preparation for cell division. Helicase enzymes are also critical for making a blueprint of a gene for protein production, a process called transcription. Further evidence suggests that Werner protein plays a critical role in repairing DNA. Overall, this protein helps maintain the structure and integrity of a person's DNA.
Proliferating cell nuclear antigen (PCNA) is a DNA clamp that acts as a processivity factor for DNA polymerase δ in eukaryotic cells and is essential for replication. PCNA is a homotrimer and achieves its processivity by encircling the DNA, where it acts as a scaffold to recruit proteins involved in DNA replication, DNA repair, chromatin remodeling and epigenetics.
Deoxyribonuclease IV (phage-T4-induced) is a kind of Endonuclease that catalyzes the degradation nucleotides in DsDNA by attacking the 5'-terminal end.
DNA-(apurinic or apyrimidinic site) lyase is an enzyme that in humans is encoded by the APEX1 gene.
Cell cycle checkpoint control protein RAD9A is a protein that in humans is encoded by the RAD9A gene.Rad9 has been shown to induce G2 arrest in the cell cycle in response to DNA damage in yeast cells. Rad9 was originally found in budding yeast cells but a human homolog has also been found and studies have suggested that the molecular mechanisms of the S and G2 checkpoints are conserved in eukaryotes. Thus, what is found in yeast cells are likely to be similar in human cells.
UV excision repair protein RAD23 homolog A is a protein that in humans is encoded by the RAD23A gene.
DNA polymerase kappa is an DNA polymerase that in humans is encoded by the POLK gene. It is involved in translesion synthesis.
The enzyme DNA-(apurinic or apyrimidinic site) lyase, also referred to as DNA-(apurinic or apyrimidinic site) 5'-phosphomonoester-lyase or DNA AP lyase catalyzes the cleavage of the C-O-P bond 3' from the apurinic or apyrimidinic site in DNA via β-elimination reaction, leaving a 3'-terminal unsaturated sugar and a product with a terminal 5'-phosphate. In the 1970s, this class of enzyme was found to repair at apurinic or apyrimidinic DNA sites in E. coli and in mammalian cells. The major active enzyme of this class in bacteria, and specifically, E. coli is endonuclease type III. This enzyme is part of a family of lyases that cleave carbon-oxygen bonds.
Flap endonuclease 1 is an enzyme that in humans is encoded by the FEN1 gene.
Cyclin-O is a protein that in humans is encoded by the CCNO gene.
G/T mismatch-specific thymine DNA glycosylase is an enzyme that in humans is encoded by the TDG gene. Several bacterial proteins have strong sequence homology with this protein.
DnaJ homolog subfamily A member 1 is a protein that in humans is encoded by the DNAJA1 gene.
Endonuclease VIII-like 1 is an enzyme that in humans is encoded by the NEIL1 gene.
Endonuclease VIII-like 2 is an enzyme that in humans is encoded by the NEIL2 gene.
ATP-dependent DNA helicase Q1 is an enzyme that in humans is encoded by the RECQL gene.
The FPG IleRS zinc finger domain represents a zinc finger domain found at the C-terminal in both DNA glycosylase/AP lyase enzymes and in isoleucyl tRNA synthetase. In these two types of enzymes, the C-terminal domain forms a zinc finger.
MutS is a mismatch DNA repair protein, originally described in Escherichia coli.
In molecular biology, the H2TH domain is a DNA-binding domain found in DNA glycosylase/AP lyase enzymes, which are involved in base excision repair of DNA damaged by oxidation or by mutagenic agents. Most damage to bases in DNA is repaired by the base excision repair pathway. These enzymes are primarily from bacteria, and have both DNA glycosylase activity EC 3.2.2.- and AP lyase activity EC 4.2.99.18. Examples include formamidopyrimidine-DNA glycosylases and endonuclease VIII (Nei).
