Bifunctional DNA Alkylator 1,3-Bis(2-chloroethyl)-1-nitrosourea Activates the ATR-Chk1 Pathway Independently of the Mismatch Repair Pathway

AUTOR(ES)

Cui, B.

FONTE

American Society for Pharmacology and Experimental Therapeutics

RESUMO

The presence of DNA damage initiates signaling through the ataxia-telangiectasia mutated kinase (ATM) and the ATM- and the Rad3-related kinase (ATR), which phosphorylate, thus activating, the checkpoint kinases (Chk) 1 and 2, which leads to cell cycle arrest. The bifunctional DNA alkylator 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) is cytotoxic primarily by inducing DNA monoadducts and ultimately, interstrand cross-links, which block DNA replication. In this study, we investigated the activation of the ATR-Chk1 pathway in response to BCNU treatment and the dependence of this response on the DNA mismatch repair (MMR) capacity. Medulloblastoma cells were exposed to low and moderate doses of BCNU, and the effects on this DNA damage signaling pathway were examined. In response to BCNU, Chk1 was found to be phosphorylated at serine 345 and exhibited increased kinase activity. Caffeine and wortmannin, which are broad-spectrum inhibitors of ATM and ATR, reduced this phosphorylation. Cell cycle analysis further revealed an accumulation of cells in the S phase in response to BCNU, an effect that was attenuated by caffeine. Small interfering RNA knockdown of ATR also reduced Chk1 phosphorylation after exposure to BCNU. However, knockdown of ATM had no effect on the observed Chk1 phosphorylation, suggesting that ATR was primarily responsible for Chk1 activation. Analysis of Chk1 activation in cells deficient in MMR proteins MutLα or MutSα indicated that the DNA damage response induced by BCNU was independent of the MMR apparatus. This MMR-independent activation seems to be the result of DNA interstrand cross-link formation.

Documentos Relacionados

• In Vivo Antiviral Activity of 1,3-Bis(2-Chloroethyl)-1-Nitrosourea
• In Vitro Studies on the Antiviral Activity of 1,3-Bis(2-Chloroethyl)-1-Nitrosourea
• The DNA crosslink-induced S-phase checkpoint depends on ATR–CHK1 and ATR–NBS1–FANCD2 pathways
• Retroviral transduction of a mutant methylguanine DNA methyltransferase gene into human CD34 cells confers resistance to O6-benzylguanine plus 1,3-bis(2-chloroethyl)-1-nitrosourea
• Glutathione, cell proliferation, and 1,3-bis-(2-chloroethyl)-1-nitrosourea in K562 leukemia.