Mismatch repair-mediated G2/M arrest by 6-thioguanine involves the ATR–Chk1 pathway

DNA mismatch repair (MMR) deficiency in human cancers is associated with resistance to a spectrum of clinically active chemotherapy drugs, including 6-thioguanine (6-TG). We and others have shown that 6-TG-induced DNA mismatches result in a prolonged G2/M cell cycle arrest followed by apoptosis in M...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 2004-05, Vol.318 (1), p.297-302
Main Authors: Yamane, Kazuhiko, Taylor, Kerri, Kinsella, Timothy J
Format: Article
Language:English
Subjects:
6-TG
Antimetabolites, Antineoplastic - pharmacology
Apoptosis - drug effects
Ataxia Telangiectasia Mutated Proteins
ATR
Base Pair Mismatch - genetics
Blotting, Western
Cell Cycle Proteins - metabolism
Checkpoint Kinase 1
Checkpoint Kinase 2
Chk1
DNA Repair - genetics
G2 Phase - drug effects
G2 Phase - physiology
G2/M checkpoint
HeLa Cells
Humans
In Situ Nick-End Labeling
Mismatch repair
Mitosis - drug effects
Mitosis - physiology
Phosphorylation
Protein Kinases - metabolism
Protein-Serine-Threonine Kinases - metabolism
RNA, Small Interfering - genetics
Signal Transduction
Thioguanine - pharmacology
Transfection
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Summary:DNA mismatch repair (MMR) deficiency in human cancers is associated with resistance to a spectrum of clinically active chemotherapy drugs, including 6-thioguanine (6-TG). We and others have shown that 6-TG-induced DNA mismatches result in a prolonged G2/M cell cycle arrest followed by apoptosis in MMR + human cancer cells, although the signaling pathways are not clearly understood. In this study, we found that prolonged (up to 4 days) treatment with 6-TG (3 μM) resulted in a progressive phosphorylation of Chk1 and Chk2 in MMR + HeLa cells, correlating temporally with a drug-induced G2/M arrest. Transfection of HeLa cells with small interfering RNA (siRNA) against the ataxia telangiectasia-related (ATR) kinase or against the Chk1 kinase destroyed the G2/M checkpoint and enhanced the apoptosis following 6-TG treatment. On the other hand, the induction of a G2/M population by 6-TG was similar in ATM −/− and ATM + human fibroblasts, suggesting that the ATM–Chk2 pathway does not play a major role in this 6-TG response. Our results indicate that 6-TG DNA mismatches activate the ATR–Chk1 pathway in the MMR + cells, resulting in a G2/M checkpoint response
ISSN:0006-291X
1090-2104
DOI:10.1016/j.bbrc.2004.04.030