Cell Cycle Regulation and Subcellular Localization of the Major Human Uracil-DNA Glycosylase

Schwartz

Journal of Biological Chemistry

et al. 2004

A chronic imbalance in DNA precursors, caused by one-carbon metabolism impairment, can result in a deficiency of DNA repair and increased DNA damage. Although indirect evidence suggests that DNA damage plays a role in neuronal apoptosis and in the pathogenesis of neurodegenerative disorders, the underlying mechanisms are poorly understood. In particular, very little is known about the role of base excision repair of misincorporated uracil in neuronal survival. To test the hypothesis that repair of DNA damage associated with uracil misincorporation is critical for neuronal survival, we employed an antisense (AS) oligonucleotide directed against uracil-DNA glycosylase encoded by the UNG gene to deplete UNG in cultured rat hippocampal neurons. AS, but not a scrambled control oligonucleotide, induced apoptosis, which was associated with DNA damage analyzed by comet assay and up-regulation of p53. UNG mRNA and protein levels were decreased within 30 min and were undetectable within 6 -9 h of exposure to the UNG AS oligonucleotide. Whereas UNG expression is significantly higher in proliferating as compared with nonproliferating cells, such as neurons, the levels of UNG mRNA were increased in brains of cystathionine ␤-synthase knockout mice, a model for hyperhomocysteinemia, suggesting that one-carbon metabolism impairment and uracil misincorporation can induce the up-regulation of UNG expression.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Suppression of Uracil-DNA Glycosylase Induces Neuronal Apoptosis

Schwartz

Journal of Biological Chemistry

et al. 2004

“…Ugi forms an essentially irreversible complex with UDG [68,69], and the specificity of the interaction [70,71] indicates that only structurally related UDGs will bind to Ugi. Furthermore, antibodies raised against homogeneous human UDG detected both mitochondrial and nuclear forms, indicating that these forms are closely related [37,64,72].…”

Section: Similarities Between the Nuclear And Mitochondrial Forms Of Udgmentioning

confidence: 94%

DNA glycosylases in the base excision repair of DNA

Krokan

Standal

Slupphaug

1997

Biochemical Journal

Self Cite

771

566

A wide range of cytotoxic and mutagenic DNA bases are removed by different DNA glycosylases, which initiate the base excision repair pathway. DNA glycosylases cleave the Nglycosylic bond between the target base and deoxyribose, thus releasing a free base and leaving an apurinic\apyrimidinic (AP) site. In addition, several DNA glycosylases are bifunctional, since they also display a lyase activity that cleaves the phosphodiester backbone 3h to the AP site generated by the glycosylase activity. Structural data and sequence comparisons have identified common features among many of the DNA glycosylases. Their active sites have a structure that can only bind extrahelical target bases, as observed in the crystal structure of human uracil-DNA glycosylase in a complex with double-stranded DNA. Nucleotide flipping is apparently actively facilitated by the enzyme. With bacteriophage T4 endonuclease V, a pyrimidine-

“…The nuclear isoform of UDG, UNG2, is present at high levels during S phase, and removes misincorporated uracil during DNA replication. Inexplicably, UNG2 expression increases by 2.8-fold during G2 [25], but at this time UNG2 is concentrated into fewer foci than during S phase [26]. These foci are somewhat reminiscent of CENP-A foci.…”

Section: Colocalization Of Cenp-a Foci With Ung2 Foci During G2mentioning

confidence: 98%

Xenopus CENP-A assembly into chromatin requires base excision repair proteins

Zeitlin

Patel

Kavli³

et al. 2005

DNA Repair

Self Cite

CENP-A is an essential histone H3 variant found in all eukaryotes examined to date. To begin to determine how CENP-A is assembled into chromatin, we developed a binding assay using sperm chromatin in cell-free extract derived from Xenopus eggs. Our data suggest that the catalytic activities of an unidentified deoxycytidine deaminase and UNG2, a uracil DNA glycosylase, are involved in CENP-A assembly. In support of this model, inhibiting deoxycytidine deaminase with zebularine, or uracil DNA glycosylase with Ugi, uracil or UTP results in a lack of detectable CENP-A on sperm DNA.Conversely, inducing DNA damage increases the level of CENP-A detected on sperm chromatin. Our data suggest that base excision repair may be involved in assembly of this histone H3 variant.3