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Melanoma Res. 1998 Dec;8(6):471-81.

Inhibition of Ku autoantigen binding activity to the E2F motif after ultraviolet B irradiation of melanocytic cells.

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Queensland Cancer Fund Laboratories, Queensland Institute of Medical Research, Herston, Australia.


In human melanocytes and a human melanoma cell line (MM96L), the level of Ku sequence-specific binding to a 37-mer oligonucleotide containing a single E2F-1 binding site of the c-myc promoter (E2cM) significantly decreased 12 24h after cytostatic exposure to 300 J/m2 ultraviolet B radiation (UVB). No UVB-induced loss was found in fibroblasts, while HeLa cells showed an earlier (4 h) but less significant decrease than melanocytic cells. Equitoxic doses of gamma radiation, cisplatin or UVC had little effect on E2cM-specific binding. The loss of Ku binding in MM96L cells was not the result of translocation of Ku or a decrease in Ku protein or DNA-dependent protein kinase activity. The level of E2cM-specific binding in MM96L cells was increased by tunicamycin (2 microg/ml), an inhibitor of N-linked glycosylation, and decreased by the glucosidase inhibitor castanospermine (50 microg/ml). These results, which parallel the reported loss in melanocytes of the cell cycle regulator pRB after UVB, suggest that the DNA binding activity of Ku is affected by post-translational modification and may play a role in regulating the cell cycle response to UVB.

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