scholarly journals Redox Regulation of Human OGG1 Activity in Response to Cellular Oxidative Stress

2006 ◽  
Vol 26 (20) ◽  
pp. 7430-7436 ◽  
Author(s):  
Anne Bravard ◽  
Monique Vacher ◽  
Barbara Gouget ◽  
Alexandre Coutant ◽  
Florence Hillairet de Boisferon ◽  
...  
Keyword(s):  
Base Excision Repair ◽  
Redox Regulation ◽  
Excision Repair ◽  
Migration Pattern ◽  
Dna Glycosylase ◽  
Reversible Inactivation ◽  
Base Excision ◽  
Oxidized Guanine ◽  
Dependent Mechanism

ABSTRACT 8-Oxoguanine (8-oxoG), a common and mutagenic form of oxidized guanine in DNA, is eliminated mainly through base excision repair. In human cells its repair is initiated by human OGG1 (hOGG1), an 8-oxoG DNA glycosylase. We investigated the effects of an acute cadmium exposure of human lymphoblastoid cells on the activity of hOGG1. We show that coinciding with alteration of the redox cellular status, the 8-oxoG DNA glycosylase activity of hOGG1 was nearly completely inhibited. However, the hOGG1 activity returned to normal levels once the redox cellular status was normalized. In vitro, the activity of purified hOGG1 was abolished by cadmium and could not be recovered by EDTA. In cells, however, the reversible inactivation of OGG1 activity by cadmium was strictly associated with reversible oxidation of the protein. Moreover, the 8-oxoG DNA glycosylase activity of purified OGG1 and that from crude extracts were modulated by cysteine-modifying agents. Oxidation of OGG1 by the thiol oxidant diamide led to inhibition of the activity and a protein migration pattern similar to that seen in cadmium-treated cells. These results suggest that cadmium inhibits hOGG1 activity mainly by indirect oxidation of critical cysteine residues and that excretion of the metal from the cells leads to normalization of the redox cell status and restoration of an active hOGG1. The results presented here unveil a novel redox-dependent mechanism for the regulation of OGG1 activity.

scholarly journals Repair of APOBEC3G-mutated retroviral DNA in vivo is facilitated by the host enzyme uracil DNA glycosylase 2

2021 ◽  
Author(s):  
Karen Salas Briceno ◽  
Susan R. Ross
Keyword(s):  
Base Excision Repair ◽  
Excision Repair ◽  
Critical Role ◽  
Dna Glycosylase ◽  
Repair System ◽  
Viral Dna ◽  
Uracil Dna Glycosylase ◽  
Base Excision

Apolipoprotein B mRNA Editing Enzyme Catalytic Subunit 3 (APOBEC3) proteins are critical for the control of infection by retroviruses. These proteins deaminate cytidines in negative strand DNA during reverse transcription, leading to G to A changes in coding strands. Uracil DNA glycosylase (UNG) is a host enzyme that excises uracils in genomic DNA, which the base excision repair machinery then repairs. Whether UNG removes uracils found in retroviral DNA after APOBEC3-mediated mutation is not clear, and whether this occurs in vivo has not been demonstrated. To determine if UNG plays a role in the repair of retroviral DNA, we used APOBEC3G (A3G) transgenic mice which we showed previously had extensive deamination of murine leukemia virus (MLV) proviruses. The A3G transgene was crossed onto an UNG and mouse APOBEC3 knockout background (UNG-/-APO-/-) and the mice were infected with MLV. We found that virus infection levels were decreased in A3G UNG-/-APO-/- compared to A3G APO-/- mice. Deep sequencing of the proviruses showed that there were significantly higher levels of G-to-A mutations in proviral DNA from A3G transgenic UNG-/-APO-/- than A3G transgenic APO-/- mice, suggesting that UNG plays a role in the repair of uracil-containing proviruses. In in vitro studies, we found that cytoplasmic viral DNA deaminated by APOBEC3G was uracilated. In the absence of UNG, the uracil-containing proviruses integrated at higher levels into the genome than did those made in the presence of UNG. Thus, UNG also functions in the nucleus prior to integration by nicking uracil-containing viral DNA, thereby blocking integration. These data show that UNG plays a critical role in the repair of the damage inflicted by APOBEC3 deamination of reverse-transcribed DNA. Importance While APOBEC3-mediated mutation of retroviruses is well-established, what role the host base excision repair enzymes play in correcting these mutations is not clear. This question is especially difficult to address in vivo . Here, we use a transgenic mouse developed by our lab that expresses human APOBEC3G and also lacks the endogenous uracil DNA glycosylase ( Ung ) gene, and show that UNG removes uracils introduced by this cytidine deaminase in MLV reverse transcripts, thereby reducing G-to-A mutations in proviruses. Furthermore, our data suggest that UNG removes uracils at two stages in infection – in unintegrated nuclear viral reverse transcribed DNA, resulting in its degradation and second, in integrated proviruses, resulting in their repair. These data suggest that retroviruses damaged by host cytidine deaminases take advantage of the host DNA repair system to overcome this damage.

scholarly journals Repair of APOBEC3G-mutated retroviral DNA in vivo is facilitated by the host enzyme uracil DNA glycosylase 2

2021 ◽  
Author(s):  
Karen Salas Briceno ◽  
Susan R. Ross
Keyword(s):  
Base Excision Repair ◽  
Excision Repair ◽  
Critical Role ◽  
Dna Glycosylase ◽  
Repair System ◽  
Viral Dna ◽  
Uracil Dna Glycosylase ◽  
Base Excision

AbstractApolipoprotein B mRNA Editing Enzyme Catalytic Subunit 3 (APOBEC3) proteins are critical for the control of infection by retroviruses. These proteins deaminate cytidines in negative strand DNA during reverse transcription, leading to G to A changes in coding strands. Uracil DNA glycosylase (UNG) is a host enzyme that excises uracils in genomic DNA, which the base excision repair machinery then repairs. Whether UNG removes uracils found in retroviral DNA after APOBEC3-mediated mutation is not clear, and whether this occurs in vivo has not been demonstrated. To determine if UNG plays a role in the repair of retroviral DNA, we used APOBEC3G (A3G) transgenic mice which we showed previously had extensive deamination of murine leukemia virus (MLV) proviruses. The A3G transgene was crossed onto an UNG and mouse APOBEC3 knockout background (UNG-/-APO-/-) and the mice were infected with MLV. We found that virus infection levels were decreased in A3G UNG-/-APO-/- compared to A3G APO-/- mice. Deep sequencing of the proviruses showed that there were significantly higher levels of G-to-A mutations in proviral DNA from A3G transgenic UNG-/-APO-/- than A3G transgenic APO-/- mice, suggesting that UNG plays a role in the repair of uracil-containing proviruses. In in vitro studies, we found that cytoplasmic viral DNA deaminated by APOBEC3G was uracilated. In the absence of UNG, the uracil-containing proviruses integrated at higher levels into the genome than did those made in the presence of UNG. Thus, UNG also functions in the nucleus prior to integration by nicking uracil-containing viral DNA, thereby blocking integration. These data show that UNG plays a critical role in the repair of the damage inflicted by APOBEC3 deamination of reverse-transcribed DNA.ImportanceWhile APOBEC3-mediated mutation of retroviruses is well-established, what role the host base excision repair enzymes play in correcting these mutations is not clear. This question is especially difficult to address in vivo. Here, we use a transgenic mouse developed by our lab that expresses human APOBEC3G and also lacks the endogenous uracil DNA glycosylase (Ung) gene, and show that UNG removes uracils introduced by this cytidine deaminase in MLV reverse transcripts, thereby reducing G-to-A mutations in proviruses. Furthermore, our data suggest that UNG removes uracils at two stages in infection – in unintegrated nuclear viral reverse transcribed DNA, resulting in its degradation and second, in integrated proviruses, resulting in their repair. These data suggest that retroviruses damaged by host cytidine deaminases take advantage of the host DNA repair system to overcome this damage.

In Vitro Base Excision Repair Assay Using Mammalian Cell Extracts

1999 ◽  
pp. 301-315 ◽  
Author(s):  
Guido Frosina ◽  
Enrico Cappelli ◽  
Paola Fortini ◽  
Eugenia Dogliotti
Keyword(s):  
Mammalian Cell ◽  
Base Excision Repair ◽  
Excision Repair ◽  
Cell Extracts ◽  
Base Excision

Studies on the base excision repair (BER) complex in Pyrococcus furiosus

2009 ◽  
Vol 37 (1) ◽  
pp. 79-82 ◽  
Author(s):  
Shinichi Kiyonari ◽  
Saki Tahara ◽  
Maiko Uchimura ◽  
Tsuyoshi Shirai ◽  
Sonoko Ishino ◽  
...  
Keyword(s):  
Base Excision Repair ◽  
Pyrococcus Furiosus ◽  
Excision Repair ◽  
Repair Process ◽  
Nuclear Antigen ◽  
Physical Interaction ◽  
Ap Endonuclease ◽  
Reading Frame ◽  
Base Excision

We have been studying the functions of PCNA (proliferating-cell nuclear antigen) for the assembly and reassembly of the replisome during replication fork progression. We have identified the functional interactions between PCNA and several proteins involved in DNA replication and repair from Pyrococcus furiosus. We recently reported that the activity of UDG (uracil–DNA glycosylase) in P. furiosus (PfuUDG) is stimulated by PCNA (PfuPCNA) in vitro, and identified an atypical PCNA-binding site, AKTLF, in the PfuUDG protein. To understand further the function of the complex in the BER (base excision repair) process, we investigated the AP (apurinic/apyrimidinic) endonuclease, which can process the BER pathway after uracil removal by UDG. Interestingly, one candidate ORF (open reading frame) for the AP endonuclease was found in the operon containing the gene encoding UDG in the P. furiosus genome. However, this ORF did not exhibit any activity. Instead, we identified the AP endonuclease activity from the other candidate gene products, and designated the protein as PfuAP. We discovered a physical interaction between PfuAP and PfuPCNA, suggesting the formation of a BER complex in one of the repair systems in P. furiosus.

scholarly journals Spontaneous Mutagenesis Is Enhanced in Apex Heterozygous Mice

2004 ◽  
Vol 24 (18) ◽  
pp. 8145-8153 ◽  
Author(s):  
Jessica Huamani ◽  
C. Alex McMahan ◽  
Damon C. Herbert ◽  
Robert Reddick ◽  
John R. McCarrey ◽  
...  
Keyword(s):  
Base Excision Repair ◽  
Germ Line ◽  
Excision Repair ◽  
Spontaneous Mutant ◽  
Spermatogenic Cells ◽  
Ap Endonuclease ◽  
Repair Activity ◽  
Base Excision ◽  
Mutant Frequency

ABSTRACT Germ line DNA directs the development of the next generation and, as such, is profoundly different from somatic cell DNA. Spermatogenic cells obtained from young adult lacI transgenic mice display a lower spontaneous mutant frequency and greater in vitro base excision repair activity than somatic cells and tissues obtained from the same mice. However, spermatogenic cells from old lacI mice display a 10-fold higher mutant frequency. This increased spontaneous mutant frequency occurs coincidentally with decreased in vitro base excision repair activity for germ cell and testicular extracts that in turn corresponds to a decreased abundance of AP endonuclease. To directly test whether a genetic diminution of AP endonuclease results in increased spontaneous mutant frequencies in spermatogenic cell types, AP endonuclease heterozygous (Apex +/−) knockout mice were crossed with lacI transgenic mice. Spontaneous mutant frequencies were significantly elevated (approximately twofold) for liver and spleen obtained from 3-month-old Apex +/− lacI + mice compared to frequencies from Apex +/+ lacI + littermates and were additionally elevated for somatic tissues from 9-month-old mice. Spermatogenic cells from 9-month-old Apex +/− lacI + mice were significantly elevated twofold compared to levels for 9-month-old Apex +/+ lacI + control mice. These data indicate that diminution of AP endonuclease has a significant effect on spontaneous mutagenesis in somatic and germ line cells.

scholarly journals MSH2–MSH6 stimulates DNA polymerase η, suggesting a role for A:T mutations in antibody genes

2005 ◽  
Vol 201 (4) ◽  
pp. 637-645 ◽  
Author(s):  
Teresa M. Wilson ◽  
Alexandra Vaisman ◽  
Stella A. Martomo ◽  
Patsa Sullivan ◽  
Li Lan ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
Base Excision Repair ◽  
Somatic Hypermutation ◽  
Excision Repair ◽  
Cytidine Deaminase ◽  
Abasic Site ◽  
Cell Extracts ◽  
Activation Induced Cytidine Deaminase ◽  
Base Excision

Activation-induced cytidine deaminase deaminates cytosine to uracil (dU) in DNA, which leads to mutations at C:G basepairs in immunoglobulin genes during somatic hypermutation. The mechanism that generates mutations at A:T basepairs, however, remains unclear. It appears to require the MSH2–MSH6 mismatch repair heterodimer and DNA polymerase (pol) η, as mutations of A:T are decreased in mice and humans lacking these proteins. Here, we demonstrate that these proteins interact physically and functionally. First, we show that MSH2–MSH6 binds to a U:G mismatch but not to other DNA intermediates produced during base excision repair of dUs, including an abasic site and a deoxyribose phosphate group. Second, MSH2 binds to pol η in solution, and endogenous MSH2 associates with the pol in cell extracts. Third, MSH2–MSH6 stimulates the catalytic activity of pol η in vitro. These observations suggest that the interaction between MSH2–MSH6 and DNA pol η stimulates synthesis of mutations at bases located downstream of the initial dU lesion, including A:T pairs.

Sign in / Sign up

Export Citation Format

Share Document