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8-oxoguanine forms a Hoogsteen base pair with adenine. Single bases in DNA can be chemically damaged by a variety of mechanisms, the most common ones being deamination, oxidation, and alkylation. These modifications can affect the ability of the base to hydrogen-bond, resulting in incorrect base-pairing, and, as a consequence, mutations in the DNA.
It acts as a 3’→5’ DNA directed proofreading exonuclease that removes incorrectly incorporated bases during replication. [10] Similarly, in Salmonella typhimurium bacteria, the 3’ to 5’ editing function employed during DNA replication is also encoded by a gene, dnaQ , which specifies a 3’ to 5’ exonuclease subunit, one of the ...
When an incorrect base pair is recognized, DNA polymerase moves backwards by one base pair of DNA. The 3'–5' exonuclease activity of the enzyme allows the incorrect base pair to be excised (this activity is known as proofreading). Following base excision, the polymerase can re-insert the correct base and replication can continue forwards.
Examples of mismatched bases include a G/T or A/C pairing (see DNA repair). Mismatches are commonly due to tautomerization of bases during DNA replication. The damage is repaired by recognition of the deformity caused by the mismatch, determining the template and non-template strand, and excising the wrongly incorporated base and replacing it ...
Base excision repair (BER): damaged single bases or nucleotides are most commonly repaired by removing the base or the nucleotide involved and then inserting the correct base or nucleotide. In base excision repair, a glycosylase [ 22 ] enzyme removes the damaged base from the DNA by cleaving the bond between the base and the deoxyribose.
Similarly, the MMR pathway only targets mismatched Watson-Crick base pairs. Nucleotide excision repair (NER) is a particularly important excision mechanism that removes DNA damage induced by ultraviolet light (UV). UV DNA damage results in bulky DNA adducts — these adducts are mostly thymine dimers and 6,4-photoproducts. Recognition of the ...
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dnaQ is the gene encoding the ε subunit of DNA polymerase III in Escherichia coli. [1] The ε subunit is one of three core proteins in the DNA polymerase complex. It functions as a 3’→5’ DNA directed proofreading exonuclease that removes incorrectly incorporated bases during replication.