What are the DNA repair pathways that repair damaged DNA bases?
What are the DNA repair pathways that repair damaged DNA bases?
At least five major DNA repair pathways—base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR) and non-homologous end joining (NHEJ)—are active throughout different stages of the cell cycle, allowing the cells to repair the DNA damage.
What is required for DNA excision repair?
In nucleotide excision repair DNA damage is removed through incision of the damaged strand on both sides of the lesion, followed by repair synthesis, which fills the gap using the intact strand as a template, and finally ligation.
How does DNA excision repair work?
In nucleotide excision repair, the damaged nucleotide(s) are removed along with a surrounding patch of DNA. In this process, a helicase (DNA-opening enzyme) cranks open the DNA to form a bubble, and DNA-cutting enzymes chop out the damaged part of the bubble.
What are the 3 steps of nucleotide excision repair?
The basic mechanism of excision repair involves: (1) damage recognition; (2) subunit assembly; (3) dual incisions that result in excision of the damage-containing oligomer; (4) resynthesis to fill in the gap; and (5) ligation to regenerate an intact molecule.
How does base excision repair work?
Base excision repair (BER) corrects small base lesions that do not significantly distort the DNA helix structure. It is initiated by a DNA glycosylase that recognizes and removes the damaged base, leaving an abasic site which is further processed by short-patch repair or long-patch repair.
How do you repair damaged DNA?
Most damage to DNA is repaired by removal of the damaged bases followed by resynthesis of the excised region. Some lesions in DNA, however, can be repaired by direct reversal of the damage, which may be a more efficient way of dealing with specific types of DNA damage that occur frequently.
What triggers base excision repair?
BER is initiated by a DNA glycosylase that recognizes and removes the damaged base, leaving an abasic site that is further processed by short-patch repair or long-patch repair that largely uses different proteins to complete BER.
What does base excision repair fix?
Base excision repair (BER) corrects DNA damage from oxidation, deamination and alkylation. Such base lesions cause little distortion to the DNA helix structure. Furthermore, other DNA glycosylases may have important roles in epigenetics, thus expanding the repertoire of BER proteins.
What happens during base excision repair?
How DNA is repaired by the nucleotide excision repair system?
In nucleotide excision repair (NER), damaged bases are cut out within a string of nucleotides, and replaced with DNA as directed by the undamaged template strand. This repair system is used to remove pyrimidine dimers formed by UV radiation as well as nucleotides modified by bulky chemical adducts.
How does DNA repair mistakes in DNA replication in eukaryotes?
Most of the mistakes during DNA replication are promptly corrected by DNA polymerase which proofreads the base that has just been added. In proofreading, the DNA pol reads the newly-added base before adding the next one so a correction can be made.
Why is base excision repair important in DNA replication?
Base excision repair is important for removing damaged bases that could otherwise cause mutations by mispairing, or could 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.
What is base excision repair?
Base excision repair is a cellular mechanism that repairs damaged DNA throughout the cell cycle. It is primarily responsible for removing small, non-helix-distorting base lesions from the genome.
What is DNA repair in mammalian cells?
DNA repair in mammalian cells: Base excision repair: the long and short of it Base excision repair (BER) is the primary DNA repair pathway that corrects base lesions that arise due to oxidative, alkylation, deamination, and depurinatiation/depyrimidination damage.
What is the BER pathway for DNA repair?
BER facilitates the repair of damaged DNA via two general pathways – short-patch and long-patch. The shortpatch BER pathway leads to a repair tract of a single nucleotide. Alternatively, the long-patch BER pathway produces a repair tract of at least two nucleotides.
