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Description

Uracil-DNA glycosylase (EC 3.2.2.27, UniProt P13051, also known as UDG) is encoded by the UNG (also known as DGU, HIGM4, HIGM5, UNG1, UNG2, UNG15) gene (Gene ID 7374) in human. Uracil-DNA glycosylases catalyze the release of uracil from DNA molecules by cleaving the N-glycosylic bond and initiating the base-excision repair (BER) pathway that plays an important role in mutagenesis prevention. Uracil bases in DNA can result from cytosine deamination or misincorporation of dUMP instead of dTTP during DNA synthesis. Alternative promoter usage and splicing of UNG gene lead to two different isoforms, the mitochondrial UNG1 and the nuclear UNG2. The mammalian shelterin complex contains the six proteins (TRF1, TRF2, RAP1, TIN2, POT1, and TPP1), the complex occupies the end of the telomeres and protect telomeres against inappropriate DNA repair when telomeres are not being lengthened. UNG deficiency in primary mouse hematopoietic cells is shown to affect POT1 (Protector of Telomeres 1) recognition of the telomere repeats due to increased uracil incorporation in telomeres TTAGGG repeats, which in turn leads to abnormal telomere lengthening.