This gene encodes one of several uracil-DNA glycosylases. One important function of uracil-DNA glycosylases is to prevent mutagenesis by eliminating uracil from DNA molecules by cleaving the N-glycosylic bond and initiating the base-excision repair (BER) pathway. Uracil bases occur from cytosine deamination or misincorporation of dUMP residues. Alternative promoter usage and splicing of this gene leads to two different isoforms: the mitochondrial UNG1 and the nuclear UNG2. The UNG2 term was used as a previous symbol for the CCNO gene (GeneID 10309), which has been confused with this gene, in the literature and some databases. [provided by RefSeq, Nov 2010],disease:Defects in UNG are a cause of immunodeficiency with hyper-IgM type 5 syndrome (HIGM5) [MIM:608106]. Hyper-IgM syndrome is a condition characterized by normal or increased serum IgM concentrations associated with low or absent serum IgG, IgA, and IgE concentrations. HIGM5 is associated with profound impairment in immunoglobulin (Ig) class-switch recombination (CSR) at a DNA precleavage step.,function:Excises uracil residues from the DNA which can arise as a result of misincorporation of dUMP residues by DNA polymerase or due to deamination of cytosine.,online information:UNG mutation db,PTM:Isoform 1 is processed by cleavage of a transit peptide.,similarity:Belongs to the uracil-DNA glycosylase family.,subunit:Monomer. Interacts with HIV-1 Vpr.,tissue specificity:Isoform 1 is widely expressed with the highest expression in skeletal muscle, heart and testicles. Isoform 2 has the highest expression levels in tissues containing proliferating cells.,