Because of the possible involvement of O6-methyldeoxyguanosine as a cytotoxic and carcinogenic lesion in pancreatic β-cells, studies were undertaken to assess the ability of rat β-cells to repair this DNA lesion. Primary cultures of neonatal rat β-cells were shown to contain very low levels of O6-methylguanine-DNA-methyltransferase activity, the predominant mechanism for repairing O6-methyldeoxyguanosine in mammalian cells. However, using a 32P-endlabeling assay to measure O6-methyldeoxyguanosine in cells after exposure to N-methyl-N-nitrosourea, it was determined that rat β-cells repaired O6-methyldeoxyguanosine to a substantial extent over a 24-h period. To elucidate the mechanism of O6-methyldeoxyguanosine repair in the virtual absence of constitutive O6-methylguanine-DNA-methyltransferase expression, studies were performed to determine if O6-methylguanine-DNA-methyltransferase expression was enhanced in N-methyl-N-nitrosourea-treated β-cells. No increase in O6-methylguanine-DNA-methyltransferase activity was detected 24 or 48 h after exposure. However, Northern blot analysis showed a two- to threefold elevation in O6-methylguanine-DNA-methyltransferase messenger RNA levels in β-cells 12 and 24 h after N-methyl-N-nitrosourea treatment. This finding is the first demonstration of a change in O6-methylguanine-DNA-methyltransferase messenger RNA levels in a cell type with low constitutive activity.
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Original Articles| August 01 1993
Repair of O6-Methylguanine in Rat Pancreatic β-Cells After Exposure to N-Methyl-N-Nitrosourea
J Wesley Nelson;
Susan P Ledoux;
Address Correspondence and reprint requeststo Glenn L. Wilso, Department of Structural and Celluar Biology, University of South Alabama, Mobile Al 36688.
J Wesley Nelson, Susan P Ledoux, Glenn L Wilson; Repair of O6-Methylguanine in Rat Pancreatic β-Cells After Exposure to N-Methyl-N-Nitrosourea. Diabetes 1 August 1993; 42 (8): 1187–1194. https://doi.org/10.2337/diab.42.8.1187
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