Allio T, Preston RJ. Increased sensitivity to chromatid aberration induction by bleomycin and neocarzinostatin results from alterations in a DNA damage response pathway.
Mutat Res 2000;
453:5-15. [PMID:
11006407 DOI:
10.1016/s0027-5107(00)00030-0]
[Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
DNA damage response pathways coordinate the cellular response to DNA damage. To investigate the roles of tumor suppressor genes in these pathways, human lymphoblastoid cells (wild-type, p53-/-, ATM-/-) were treated for 1 h with 0-3 microg/ml of the radiomimetic compound bleomycin (BLM), and cells treated in G(2) were analyzed for chromatid aberrations. BLM-induced aberration frequencies were significantly increased, to the greatest extent in the ATM-/- cells and, to a lesser extent, in the p53-/- cells compared to wild-type cells. These observations are consistent with p53 and ATM acting in a damage response pathway activated by DNA strand breaks. The consequences of disrupting this pathway were further investigated by studies using wortmannin, a PI-3 kinase and DNA repair inhibitor. Wortmannin significantly increased the BLM-induced aberration frequencies in all but the ATM-/- cells, elevating the sensitivity of p53-/- cells to ATM-/- levels and that of wild-type cells to intermediate levels. These differential sensitivities suggest that the ATM phenotype is the result of dual cellular defects, one involving p53 and the other a wortmannin-sensitive component. Similar studies in Brca1+/- and Brca2+/- human lymphoblasts showed no increased sensitization to BLM in the absence of inhibitor, and differential sensitization by wortmannin. To determine if there was any substrate specificity for p53- and ATM-mediated DNA damage responses, chromatid aberrations were assessed in wild-type, p53-/-, and ATM-/- cells exposed to 0-0.4 microg/ml neocarzinostatin (NCS) for 1 h. In contrast to results with BLM, the p53-/- cells exhibited a low sensitivity to NCS-induced aberrations, similar to wild-type, while ATM-/- cells remained highly sensitive. This suggests that the response to BLM- and NCS-induced lesions involves different mechanisms.
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