Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An essential step in the repair of free radical-mediated DNA strand breaks is the removal of sugar fragments such as phosphoglycolate from the 3' termini. While the abasic endonuclease Ape1 can remove phosphoglycolate from single-strand breaks in double-stranded DNA, an enzyme capable of removing it from 3' overhangs of double-strand breaks has yet to be identified. We therefore tested DNase III, the predominant 3' --> 5' exonuclease in mammalian cell extracts, for possible 3'-phosphoglycolate-removing activity. However, all 3'-phosphoglycolate substrates, as well as a 3'-phosphate substrate, were resistant to DNase III under conditions in which the analogous 3'-hydroxyl substrates were extensively degraded. The DNA end-binding protein Ku (an equimolar mixture of Ku70, now known as G22P1, and Ku86, now known as XRCC5) did not alter the resistance of the 3'-phosphoglycolate substrates, but the protein modulated the susceptibility of 3'-hydroxyl substrates, allowing DNase III to remove a 3' overhang but inhibiting digestion of the double-stranded portion of the substrate.
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PMID:Resistance of 3'-phosphoglycolate DNA ends to digestion by mammalian DNase III. 1183 93

The aims of this study were to investigate mechanisms of action involved in H2AX phosphorylation by DNA interstrand crosslinking (ICL) agents and determine whether gammaH2AX could be a suitable pharmacological marker for identifying potential ICL cellular chemosensitivity. In normal human fibroblasts, after treatment with nitrogen mustard (HN2) or cisplatin, the peak gammaH2AX response was detected 2-3 h after the peak of DNA ICLs measured using the comet assay, a validated method for detecting ICLs in vitro or in clinical samples. Detection of gammaH2AX foci by immunofluorescence microscopy could be routinely detected with 6-10 times lower concentrations of both drugs compared to detection of ICLs using the comet assay. A major pathway for repairing DNA ICLs is the initial unhooking of the ICL by the ERCC1-XPF endonuclease followed by homologous recombination. HN2 or cisplatin-induced gammaH2AX foci persisted significantly longer in both, ERCC1 or XRCC3 (homologous recombination) defective Chinese hamster cells that are highly sensitive to cell killing by ICL agents compared to wild type or ionising radiation sensitive XRCC5 cells. An advantage of using gammaH2AX immunofluorescence over the comet assay is that it appears to detect ICL chemosensitivity in both ERCC1 and HR defective cells. With HN2 and cisplatin, gammaH2AX foci also persisted in chemosensitive human ovarian cancer cells (A2780) compared to chemoresistant (A2780cisR) cells. These results show that gammaH2AX can act as a highly sensitive and general marker of DNA damage induced by HN2 or cisplatin and shows promise for predicting potential cellular chemosensitivity to ICL agents.
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PMID:Histone H2AX phosphorylation as a molecular pharmacological marker for DNA interstrand crosslink cancer chemotherapy. 1850 35