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Factors modifying 3-aminobenzamide cytotoxicity in normal and repair-deficient human fibroblasts
Abstract:
3-Aminobenzamide (3-AB), an inhibitor of poly(ADP-ribosylation), is lethal to human fibroblasts with damaged DNA. Its cytotoxicity was determined relative to a number of factors including the types of lesions, the kinetics of repair, and the availability of alternative repair systems. A variety of alkylating agents, UV or gamma irradiation, or antimetabolites were used to create DNA lesions. 3-AB enhanced lethality with monofunctional alkylating agents only. Within this class of compounds, methylmethanesulfonate (MMS) treatments made cells more sensitive to 3-AB than did treatment with methylnitrosourea (MNU) or methylnitronitrosoguanidine (MNNG). 3-AB interfered with a dynamic repair process lasting several days, since human fibroblasts remained sensitive to 3-AB for 36-48 hours following MMS treatment. During this same interval, 3-AB caused these cells to arrest in G2 phase. Alkaline elution analysis also revealed that this slow repair was delayed further by 3-AB. Human mutant cells defective in DNA repair differed in their responses to 3-AB. Among mutants sensitive to monofunctional alkylating agents, ataxia telangiectasia cells were slightly more sensitive to 3-AB than control cells, while Huntington's disease cells had a near-normal response. Among UV-sensitive strains, xeroderma pigmentosum variant (XPV) cells were more sensitive to 3-AB after MMS than were XP complementation group A (A) cells, which responded normally. Greater lethality with 3-AB could be dependent on inability of the mutant cells to repair damage by other processes.
Insights
3-Aminobenzamide (3-AB) is lethal to human cells with DNA damage, particularly when exposed to monofunctional alkylating agents like MMS. This DNA repair inhibitor impacts cell cycle progression and repair kinetics, with varying sensitivity observed in DNA repair-deficient mutant cells.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- 3-Aminobenzamide (3-AB) is a known inhibitor of poly(ADP-ribosylation).
- DNA damage can trigger cell death, especially in human fibroblasts.
- The cytotoxicity of 3-AB is influenced by DNA lesion type, repair kinetics, and alternative repair pathways.
Purpose of the Study:
- To investigate the cytotoxicity of 3-Aminobenzamide (3-AB) in human fibroblasts with DNA damage.
- To determine how DNA lesion types, repair kinetics, and alternative repair systems affect 3-AB's lethality.
- To examine the differential responses of DNA repair-mutant human cells to 3-AB.
Main Methods:
- Induction of DNA lesions using various agents (alkylating agents, UV/gamma irradiation, antimetabolites).
- Assessment of cell lethality and sensitivity to 3-AB.
- Analysis of cell cycle progression (G2 arrest) and DNA repair kinetics using alkaline elution.
- Testing 3-AB sensitivity in human mutant cell lines (ataxia telangiectasia, Huntington's disease, xeroderma pigmentosum variants).
Main Results:
- 3-AB enhanced lethality specifically with monofunctional alkylating agents, with MMS treatment causing greater sensitivity than MNU or MNNG.
- Human fibroblasts remained sensitive to 3-AB for 36-48 hours post-MMS treatment, indicating interference with a prolonged repair process.
- 3-AB induced G2 phase arrest and further delayed slow DNA repair in MMS-treated cells.
- DNA repair-deficient mutant cells exhibited varied responses: ataxia telangiectasia cells were slightly more sensitive, Huntington's disease cells near-normal, and xeroderma pigmentosum variant cells more sensitive than XP group A cells after MMS exposure.
Conclusions:
- The lethality of 3-AB is strongly associated with the cellular response to specific DNA damaging agents, particularly monofunctional alkylating agents.
- 3-AB interferes with a dynamic, multi-day DNA repair process and can induce cell cycle arrest.
- Differential sensitivity of DNA repair-mutant cells suggests that the ability to utilize alternative repair pathways influences 3-AB-induced cytotoxicity.