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O6-alkylguanine DNA lesions trigger apoptosis
W Meikrantz1, M A Bergom, A Memisoglu
1Department of Cancer Cell Biology, Harvard School of Public Health, Boston, MA 02115, USA.
Abstract:
It is unclear whether alkylating agents induce apoptosis because they damage DNA, or because they damage other cellular targets. Isogenic Chinese hamster ovary (CHO) cell lines varying in the repair of O6-alkylguanine (O6AlkG) were examined for their propensity to undergo alkylation-induced apoptosis. Robust O6AlkG repair virtually eliminated the apoptogenic effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU, carmustine), as did the expression of BCL-2. O6AlkG repair had no effect on apoptosis induced by tumor necrosis factor alpha or by gamma-irradiation. We conclude that alkylating agents induce apoptosis by virtue of their ability to modify DNA bases and, more specifically, that O6AlkG lesions can trigger such programmed cell death.
Insights
Alkylating agents trigger programmed cell death (apoptosis) by damaging DNA bases, specifically O6-alkylguanine lesions. Efficient repair of these DNA lesions significantly reduces alkylation-induced apoptosis.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Alkylating agents are used in cancer therapy but their mechanism of inducing apoptosis is not fully understood.
- It remains unclear if DNA damage or other cellular targets are responsible for alkylation-induced apoptosis.
Purpose of the Study:
- To investigate the role of O6-alkylguanine (O6AlkG) repair in alkylation-induced apoptosis.
- To determine if specific DNA base modifications trigger programmed cell death.
Main Methods:
- Utilized isogenic Chinese hamster ovary (CHO) cell lines with varying O6AlkG repair capacities.
- Examined apoptosis induction by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and BCNU (carmustine).
- Assessed the impact of BCL-2 expression and O6AlkG repair on apoptosis.
Main Results:
- Robust O6AlkG repair significantly reduced apoptosis induced by MNNG and BCNU.
- BCL-2 expression also diminished alkylation-induced apoptosis.
- O6AlkG repair did not affect apoptosis induced by tumor necrosis factor alpha or gamma-irradiation.
Conclusions:
- Alkylating agents induce apoptosis primarily through DNA base modification.
- O6-alkylguanine lesions are specifically implicated as triggers of programmed cell death.
- DNA repair pathways play a crucial role in modulating sensitivity to alkylating agent-induced apoptosis.