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Uracil-DNA glycosylase (also known as UNG or UDG) is an enzyme. Its most important function is to prevent mutagenesis by eliminating uracil from DNA molecules by cleaving the N-glycosidic bond and initiating the base-excision repair (BER) pathway.
UNG is known to be the major player in uracil removal but when depleted SMUG1 can provide a backup for UNG in the antibody diversification process. [11] [12] In addition to uracil, SMUG1 removes several pyrimidine oxidation products. [13] and has a specific function to remove the thymine oxidation product 5-hydroxymethyl uracil from DNA. [14]
Some glycosylase-lyases can further perform δ-elimination, which converts the 3' aldehyde to a 3' phosphate. A wide variety of glycosylases have evolved to recognize different damaged bases. Examples of DNA glycosylases include Ogg1, which recognizes 8-oxoguanine, MPG, which recognizes 3-methyladenine, and UNG, which removes uracil from DNA.
There are two main classes of glycosylases: monofunctional and bifunctional. Monofunctional glycosylases have only glycosylase activity, whereas bifunctional glycosylases also possess AP lyase activity that permits them to cut the phosphodiester bond of DNA, creating a single-strand break without the need for an AP endonuclease.
Very short patch (VSP) repair is a DNA repair system that removes GT mismatches created by the deamination of 5-methylcytosine to thymine.This system exists because the glycosylases which normally target deaminated bases cannot target thymine (it being one of the regular four bases in DNA).
Double-stranded uracil-DNA glycosylase (EC 3.2.2.28, Mug, double-strand uracil-DNA glycosylase, Dug, dsUDG, double-stranded DNA specific UDG, dsDNA specific UDG, UdgB, G:T/U mismatch-specific DNA glycosylase, UDG) is an enzyme with systematic name uracil-double-stranded DNA deoxyribohydrolase (uracil-releasing).
The uracil may be excised by uracil-DNA glycosylase (UNG), resulting in an abasic site. This abasic site (or AP, apurinic/apyrimidinic) may be copied by a translesion synthesis DNA polymerase such as DNA polymerase eta, resulting in random incorporation of any of the four nucleotides, i.e. A, G, C, or T.
Therefore, if there were an organism that used uracil in its DNA, the deamination of cytosine (which undergoes base pairing with guanine) would lead to formation of uracil (which would base pair with adenine) during DNA synthesis. Uracil-DNA glycosylase excises uracil bases from double-stranded DNA. This enzyme would therefore recognize and cut ...