Progress in high-throughput assays of MGMT and APE1 activities in cell extracts.

2.50
Hdl Handle:
http://hdl.handle.net/10146/232073
Title:
Progress in high-throughput assays of MGMT and APE1 activities in cell extracts.
Authors:
Georgiadis, Panagiotis; Polychronaki, Nektaria; Kyrtopoulos, Soterios A.
Abstract:
DNA repair activity is of interest as a potential biomarker of individual susceptibility to genotoxic agents. In view of the current trend for exploitation of large cohorts in molecular epidemiology projects, there is a pressing need for the development of phenotypic DNA repair assays that are high-throughput, very sensitive, inexpensive and reliable. Towards this goal we have developed and validated two phenotypic assays for the measurement of two DNA repair enzymes in cell extracts: (1) O(6)-methylguanine-DNA-methyltransferase (MGMT), which repairs the O(6)-alkylguanine-type of adducts induced in DNA by alkylating genotoxins; and (2) apurinic/apyrimidinic endonuclease 1 (APE 1), which participates in base excision repair (BER) by causing a rate-limiting DNA strand cleavage 5' to the abasic sites. The MGMT assay makes use of the fact that: (a) the enzyme works by irreversibly transferring the alkyl group from the O(6) position of guanine to a cystein residue in its active site and thereby becomes inactivated and (b) that the free base O(6)-benzylguanine (BG) is a very good substrate for MGMT. In the new assay, cell extracts are incubated with BG tagged with biotin and the resulting MGMT-BG-biotin complex is immobilized on anti-MGMT-coated microtiter plates, followed by quantitation using streptavidin-conjugated alkaline phosphatase and a chemiluminescence-producing substrate. A one-step/one-tube phenotypic assay for APE1 activity has been developed based on the use of a fluorescent molecular beacon (partially self-complementary oligonucleotide with a hairpin-loop structure carrying a fluorophore and a quencher at each end). It also contains a single tetrahydrofuran residue (THF) which is recognized and cleaved by APE1, and the subsequently formed single-stranded oligomer becomes a fluorescence signal emitter. Both assays are highly sensitive, require very small amounts of protein extracts, are relatively inexpensive and can be easily automated. They have been extensively validated and are being used in the context of large-scale molecular epidemiology studies.
Citation:
Mutat. Res. 2012, 736 (1-2):25-32
Journal:
Mutation Research
Issue Date:
17-May-2012
URI:
http://hdl.handle.net/10146/232073
DOI:
10.1016/j.mrfmmm.2012.05.002
PubMed ID:
22609488
Additional Links:
http://www.sciencedirect.com/science/article/pii/S0027510712001091
Type:
Article; Preprint
Language:
en
ISSN:
0027-5107
Sponsors:
This work was partly supported by the ECNIS (Environmental Cancer, Nutrition and Individual Susceptibility) Network of Excellence of the European Union (contract no. 513943).
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Full metadata record

DC FieldValue Language
dc.contributor.authorGeorgiadis, Panagiotisen_GB
dc.contributor.authorPolychronaki, Nektariaen_GB
dc.contributor.authorKyrtopoulos, Soterios A.en_GB
dc.date.accessioned2012-07-04T10:30:29Z-
dc.date.available2012-07-04T10:30:29Z-
dc.date.issued2012-05-17-
dc.identifier.citationMutat. Res. 2012, 736 (1-2):25-32en_GB
dc.identifier.issn0027-5107-
dc.identifier.pmid22609488-
dc.identifier.doi10.1016/j.mrfmmm.2012.05.002-
dc.identifier.urihttp://hdl.handle.net/10146/232073-
dc.description.abstractDNA repair activity is of interest as a potential biomarker of individual susceptibility to genotoxic agents. In view of the current trend for exploitation of large cohorts in molecular epidemiology projects, there is a pressing need for the development of phenotypic DNA repair assays that are high-throughput, very sensitive, inexpensive and reliable. Towards this goal we have developed and validated two phenotypic assays for the measurement of two DNA repair enzymes in cell extracts: (1) O(6)-methylguanine-DNA-methyltransferase (MGMT), which repairs the O(6)-alkylguanine-type of adducts induced in DNA by alkylating genotoxins; and (2) apurinic/apyrimidinic endonuclease 1 (APE 1), which participates in base excision repair (BER) by causing a rate-limiting DNA strand cleavage 5' to the abasic sites. The MGMT assay makes use of the fact that: (a) the enzyme works by irreversibly transferring the alkyl group from the O(6) position of guanine to a cystein residue in its active site and thereby becomes inactivated and (b) that the free base O(6)-benzylguanine (BG) is a very good substrate for MGMT. In the new assay, cell extracts are incubated with BG tagged with biotin and the resulting MGMT-BG-biotin complex is immobilized on anti-MGMT-coated microtiter plates, followed by quantitation using streptavidin-conjugated alkaline phosphatase and a chemiluminescence-producing substrate. A one-step/one-tube phenotypic assay for APE1 activity has been developed based on the use of a fluorescent molecular beacon (partially self-complementary oligonucleotide with a hairpin-loop structure carrying a fluorophore and a quencher at each end). It also contains a single tetrahydrofuran residue (THF) which is recognized and cleaved by APE1, and the subsequently formed single-stranded oligomer becomes a fluorescence signal emitter. Both assays are highly sensitive, require very small amounts of protein extracts, are relatively inexpensive and can be easily automated. They have been extensively validated and are being used in the context of large-scale molecular epidemiology studies.en_GB
dc.description.sponsorshipThis work was partly supported by the ECNIS (Environmental Cancer, Nutrition and Individual Susceptibility) Network of Excellence of the European Union (contract no. 513943).en_GB
dc.languageENG-
dc.language.isoenen
dc.relation.urlhttp://www.sciencedirect.com/science/article/pii/S0027510712001091en_GB
dc.rightsArchived with thanks to Mutation researchen_GB
dc.subjectmolecular epidemiologyen_GB
dc.subjectPhenotypic assaysen_GB
dc.subjectDNA repairen_GB
dc.subjectEnzymesen_GB
dc.subjectGenotoxic agentsen_GB
dc.subjectMGMTen_GB
dc.subjectAPE1en_GB
dc.titleProgress in high-throughput assays of MGMT and APE1 activities in cell extracts.en
dc.typeArticleen
dc.typePreprinten
dc.identifier.journalMutation Researchen_GB
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