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A germline polymorphism of thymine DNA glycosylase induces genomic instability and cellular transformation.

Sjolund A, Nemec AA, Paquet N, Prakash A, Sung P, Doublié S, Sweasy JB - PLoS Genet. (2014)

Bottom Line: The rs4135113 single nucleotide polymorphism (SNP) of TDG is found in 10% of the global population.This coding SNP results in the alteration of Gly199 to Ser.The persistent accumulation of abasic sites in cells expressing G199S leads to the induction of double-strand breaks (DSBs).

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America.

ABSTRACT
Thymine DNA glycosylase (TDG) functions in base excision repair, a DNA repair pathway that acts in a lesion-specific manner to correct individual damaged or altered bases. TDG preferentially catalyzes the removal of thymine and uracil paired with guanine, and is also active on 5-fluorouracil (5-FU) paired with adenine or guanine. The rs4135113 single nucleotide polymorphism (SNP) of TDG is found in 10% of the global population. This coding SNP results in the alteration of Gly199 to Ser. Gly199 is part of a loop responsible for stabilizing the flipped abasic nucleotide in the active site pocket. Biochemical analyses indicate that G199S exhibits tighter binding to both its substrate and abasic product. The persistent accumulation of abasic sites in cells expressing G199S leads to the induction of double-strand breaks (DSBs). Cells expressing the G199S variant also activate a DNA damage response. When expressed in cells, G199S induces genomic instability and cellular transformation. Together, these results suggest that individuals harboring the G199S variant may have increased risk for developing cancer.

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Related in: MedlinePlus

Expression of G199S leads to induction of chromosomal aberrations.Representative image of metaphase spreads of MCF10A pools expressing (A) WT or (B) G199S. Chromosomal breaks are noted with arrows and fusions are noted with *. C. Graph illustrating the average number of aberrations per metaphase. A total of at least 50 metaphases were scored for each cell line. Data are graphed as mean ± SD. ** and * denote p<0.01 and P<0.05, respectively.
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pgen-1004753-g006: Expression of G199S leads to induction of chromosomal aberrations.Representative image of metaphase spreads of MCF10A pools expressing (A) WT or (B) G199S. Chromosomal breaks are noted with arrows and fusions are noted with *. C. Graph illustrating the average number of aberrations per metaphase. A total of at least 50 metaphases were scored for each cell line. Data are graphed as mean ± SD. ** and * denote p<0.01 and P<0.05, respectively.

Mentions: Recent work has shown that expression of a germline variant of the nth endonuclease III-like (NTH1) DNA glycosylase as well as several germline and tumor-associated variants of DNA polymerase β induce genomic instability in the form of chromosomal aberrations [21]–[24]. Given this, and the fact that G199S binds more tightly to its abasic product leading to activation of the DNA damage response and the accumulation of DSBs, we asked if expression of G199S in MCF10A human breast epithelial cells leads to the generation of chromosomal aberrations. Analysis of metaphase spreads shows significantly more breaks and fragments are present in G199S cells compared to WT (Figure 6). These data suggest that expression of G199S leads to increased levels of genomic instability in the form of chromosomal aberrations.


A germline polymorphism of thymine DNA glycosylase induces genomic instability and cellular transformation.

Sjolund A, Nemec AA, Paquet N, Prakash A, Sung P, Doublié S, Sweasy JB - PLoS Genet. (2014)

Expression of G199S leads to induction of chromosomal aberrations.Representative image of metaphase spreads of MCF10A pools expressing (A) WT or (B) G199S. Chromosomal breaks are noted with arrows and fusions are noted with *. C. Graph illustrating the average number of aberrations per metaphase. A total of at least 50 metaphases were scored for each cell line. Data are graphed as mean ± SD. ** and * denote p<0.01 and P<0.05, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4222680&req=5

pgen-1004753-g006: Expression of G199S leads to induction of chromosomal aberrations.Representative image of metaphase spreads of MCF10A pools expressing (A) WT or (B) G199S. Chromosomal breaks are noted with arrows and fusions are noted with *. C. Graph illustrating the average number of aberrations per metaphase. A total of at least 50 metaphases were scored for each cell line. Data are graphed as mean ± SD. ** and * denote p<0.01 and P<0.05, respectively.
Mentions: Recent work has shown that expression of a germline variant of the nth endonuclease III-like (NTH1) DNA glycosylase as well as several germline and tumor-associated variants of DNA polymerase β induce genomic instability in the form of chromosomal aberrations [21]–[24]. Given this, and the fact that G199S binds more tightly to its abasic product leading to activation of the DNA damage response and the accumulation of DSBs, we asked if expression of G199S in MCF10A human breast epithelial cells leads to the generation of chromosomal aberrations. Analysis of metaphase spreads shows significantly more breaks and fragments are present in G199S cells compared to WT (Figure 6). These data suggest that expression of G199S leads to increased levels of genomic instability in the form of chromosomal aberrations.

Bottom Line: The rs4135113 single nucleotide polymorphism (SNP) of TDG is found in 10% of the global population.This coding SNP results in the alteration of Gly199 to Ser.The persistent accumulation of abasic sites in cells expressing G199S leads to the induction of double-strand breaks (DSBs).

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America.

ABSTRACT
Thymine DNA glycosylase (TDG) functions in base excision repair, a DNA repair pathway that acts in a lesion-specific manner to correct individual damaged or altered bases. TDG preferentially catalyzes the removal of thymine and uracil paired with guanine, and is also active on 5-fluorouracil (5-FU) paired with adenine or guanine. The rs4135113 single nucleotide polymorphism (SNP) of TDG is found in 10% of the global population. This coding SNP results in the alteration of Gly199 to Ser. Gly199 is part of a loop responsible for stabilizing the flipped abasic nucleotide in the active site pocket. Biochemical analyses indicate that G199S exhibits tighter binding to both its substrate and abasic product. The persistent accumulation of abasic sites in cells expressing G199S leads to the induction of double-strand breaks (DSBs). Cells expressing the G199S variant also activate a DNA damage response. When expressed in cells, G199S induces genomic instability and cellular transformation. Together, these results suggest that individuals harboring the G199S variant may have increased risk for developing cancer.

Show MeSH
Related in: MedlinePlus