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The Fanconi anemia complementation group C protein corrects DNA interstrand cross-link-specific apoptosis in HSC536N
U K Marathi1, S R Howell, R A Ashmun
1Department of Molecular Pharmacology, St Jude Children's Research Hospital Memphis, TN 38101, USA.
Abstract:
Fanconi anemia (FA) cells are hypersensitive to cytotoxicity, cell cycle arrest, and chromosomal aberrations induced by DNA cross-linking agents, such as mitomycin C (MMC) and nitrogen mustard (HN2). Although MMC hypersensitivity is complemented in a subset of FA cells (complementation group C [FA-C]) by wild-type FAC cDNA, the cytoprotective mechanism is unknown. In the current study, we tested the hypothesis that FAC protein functions in the suppression of DNA interstand cross-link (ISC)-induced cell cycle arrest and apoptosis. Comparison of HN2-induced cell cycle arrest and apoptosis with those of its non-cross-linking analogs, diethylaminoethyl chloride and 2-dimethylaminoethyl chloride, delineated the DNA ISC specificity of FAC-mediated cytoprotection. Overexpression of wild-type FAC cDNA in FA-C lymphoblasts (HSC536N cell line) prevented HN2-induced growth inhibition, G2 arrest, and DNA fragmentation that is characteristic of apoptosis. In contrast cytoprotection was not conferred against the effects of the non-cross-linking mustards. Our data show that DNA ISCs induce apoptosis more potently than do DNA monoadducts and suggest that FAC suppresses specifically DNA ISC-induced apoptosis in the G2 phase of the cell cycle.
Insights
Fanconi anemia (FA) cells exhibit sensitivity to DNA cross-linking agents. The FAC protein specifically suppresses DNA interstrand cross-link-induced apoptosis in FA-C cells, protecting them from cell cycle arrest and cytotoxicity.
Area of Science:
- Genetics
- Molecular Biology
- Cell Biology
Background:
- Fanconi anemia (FA) is a rare genetic disorder characterized by genomic instability.
- FA cells show hypersensitivity to DNA cross-linking agents, leading to cell cycle arrest and chromosomal aberrations.
- The precise cytoprotective mechanism of the FAC protein in FA complementation group C (FA-C) remains unclear.
Purpose of the Study:
- To investigate the role of the FAC protein in suppressing cell cycle arrest and apoptosis induced by DNA interstrand cross-links (ISCs).
- To determine if FAC-mediated cytoprotection is specific to DNA ISCs.
Main Methods:
- Comparison of cell cycle arrest and apoptosis induced by nitrogen mustard (HN2) and its non-cross-linking analogs.
- Overexpression of wild-type FAC cDNA in FA-C lymphoblasts (HSC536N cell line).
- Assessment of growth inhibition, G2 arrest, and DNA fragmentation.
Main Results:
- FAC protein overexpression prevented HN2-induced growth inhibition, G2 arrest, and apoptosis in FA-C cells.
- Cytoprotection was specific to DNA ISCs, as non-cross-linking analogs did not elicit the same protective effect.
- DNA ISCs were found to induce apoptosis more potently than DNA monoadducts.
Conclusions:
- The FAC protein specifically suppresses DNA ISC-induced apoptosis in the G2 phase of the cell cycle.
- This finding elucidates a key cytoprotective mechanism in Fanconi anemia complementation group C.
- The study highlights the differential cellular response to DNA ISCs versus monoadducts.