Oxidation Status of Human OGG1-S326C Polymorphic Variant Determines Cellular DNA Repair Capacity

Abstract

The hOGG1 gene encodes the DNA glycosylase that removes the mutagenic lesion 7,8-dihyro-8-oxoguanine (8-oxoG) from DNA. A frequently found polymorphism resulting in a serine to cysteine substitution at position 326 of the OGG1 protein has been associated in several molecular epidemiologic studies with cancer development. To investigate whether the variant allele encodes a protein with altered OGG1 function, we compared the 8-oxoG repair activity, both in vivo and in cell extracts, of lymphoblastoid cell lines established from individuals carrying either Ser/Ser or Cys/Cys genotypes. We show that cells homozygous for the Cys variant display increased genetic instability and reduced in vivo 8-oxoG repair rates. Consistently, their extracts have an almost 2-fold lower basal 8-oxoG DNA glycosylase activity when compared with the Ser variant. Treatment with reducing agents of either the Cys variant cells directly or of protein extracts from these cells increases the repair capacity to the level of the Ser variant, whereas it does not affect the activity in cells or extracts from the latter. Furthermore, the DNA glycosylase activity of cells carrying the Cys/Cys alleles is more sensitive to inactivation by oxidizing agents when compared with that of the Ser/Ser cells. Analysis of the redox status of the OGG1 protein in the cells confirms that the lower activity of OGG1-Cys326 is associated with the oxidation of Cys326 to form a disulfide bond. Our findings support the idea that individuals homozygous for the OGG1-Cys variant could more readily accumulate mutations under conditions of oxidative stress.

Inducible response required for repair of low-dose radiation damage in human fibroblasts

“…Strikingly, at least one of the six genes (Nek1) appears to be involved in DNA damage responses following IR, and its loss is associated with radiosensitivity and impaired DSB repair (32,33). This finding is in line with other recent observations indicating that oxidative stress on proteins can modify their structure and function (36)(37)(38)(39).…”

Redox Regulation of DNA Repair: Implications for Human Health and Cancer Therapeutic Development

“…The reversible inactivation of OGG1 activity by cadmium was strictly associated with reversible oxidation of the protein, as demonstrated by the use of cysteine-modifying agents, such as diamide, with the pure protein and crude extracts (30). A frequently found polymorphism of OGG1, S326C OGG1, associated with cancer development, has been shown to have lower 8-oxoG DNA glycosylase activity, and the lower activity of OGG1-Cys326 is associated with the easy oxidation of Cys326 to form a disulfide bond (31). In this study, the 8-oxoG repair activity was analyzed in the cells and cell extracts of lymphoblastoid cell lines established from individuals carrying either Ser=Ser or Cys=Cys genotypes.…”

The C/A polymorphism in intron 11 of the XPC gene plays a crucial role in the modulation of an individual’s susceptibility to sporadic colorectal cancer

“…The 8-oxoguanine DNA glycosyslase (OGG1) gene encodes a DNA repair protein that removes 8-oxo-7,8-dihydroguanine (8-oxoG) [6]. The variant allele of the Ser326Cys polymorphism is associated with higher level of genetic instability and seems to be associated with an increased risk of lung, esophagus, prostate cancer as well as ALL (acute lymphoblastic leukemia) among children [7][8][9]. Opinion is divided as to whether there is an association between OGG1, Ser326Cys and colorectal cancer [8,10,11].…”