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ATR inhibition selectively sensitizes G1 checkpoint-deficient cells to lethal premature chromatin condensation
1Department of Chemistry and Chemical Biology, Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA.
Abstract:
Premature chromatin condensation (PCC) is a hallmark of mammalian cells that begin mitosis before completing DNA replication. This lethal event is prevented by a highly conserved checkpoint involving an unknown, caffeine-sensitive mediator. Here, we have examined the possible involvement of the caffeine-sensitive ATM and ATR protein kinases in this checkpoint. We show that caffeine's ability to inhibit ATR (but not ATM) causes PCC, that ATR (but not ATM) prevents PCC, and that ATR prevents PCC via Chk-1 regulation. Moreover, mimicking cancer cell phenotypes by disrupting normal G(1) checkpoints sensitizes cells to PCC by ATR inhibition plus low-dose DNA damage. Notably, loss of p53 function potently sensitizes cells to PCC caused by ATR inhibition by a small molecule. We present a molecular model for how ATR prevents PCC and suggest that ATR represents an attractive therapeutic target for selectively killing cancer cells by premature chromatin condensation.
Insights
A cell cycle checkpoint involving ATR protein kinase prevents premature chromatin condensation (PCC). Inhibiting ATR triggers PCC, offering a potential strategy for targeting cancer cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Premature chromatin condensation (PCC) is a lethal event in cells that enter mitosis before DNA replication is complete.
- A conserved checkpoint, mediated by a caffeine-sensitive factor, normally prevents PCC.
- The roles of ATM and ATR protein kinases in this checkpoint were investigated.
Purpose of the Study:
- To determine if ATM or ATR protein kinases are involved in the checkpoint that prevents PCC.
- To elucidate the molecular mechanism by which ATR prevents PCC.
- To explore the therapeutic potential of targeting ATR for cancer treatment.
Main Methods:
- Utilized caffeine to inhibit ATM and ATR kinases.
- Assessed the effects of kinase inhibition on PCC.
- Investigated the role of Chk-1 in ATR-mediated PCC prevention.
- Examined the impact of disrupted G1 checkpoints and p53 loss on PCC sensitivity.
Main Results:
- Caffeine inhibition of ATR, but not ATM, induced PCC.
- ATR, not ATM, was found to prevent PCC.
- ATR prevents PCC through the regulation of Chk-1.
- Disrupting G1 checkpoints and loss of p53 function sensitized cells to ATR inhibition-induced PCC, especially with low-dose DNA damage.
Conclusions:
- ATR kinase plays a crucial role in preventing premature chromatin condensation.
- ATR prevents PCC via Chk-1 regulation, forming a key component of the cell cycle checkpoint.
- ATR inhibition, particularly in cancer cells with compromised G1 checkpoints or p53 loss, represents a potential therapeutic strategy for inducing selective cell death via PCC.