When the rat hepatoma cell line H4IIE was treated with DNA‐damaging agents such as N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG), ultraviolet light and γ‐rays, the O6‐methylguanine‐DNA methyltransferase activity increased 2 to 3 times over the level seen in non‐treated cells. SDS/polyacrylamide gel electrophoresis followed by fluorography revealed that a single species of methyltransferase protein with a molecular weight of 25,500 was present in both non‐treated and treated cells. Northern blot analysis using a cloned rat cDNA as a probe revealed that the enzyme activity increased because transcription of the gene was enhanced. The level of enzyme activity increased within 48 h after UV irradiation and remained at a higher level for 150 h. Following UV irradiation, the cells become more resistant than the normal cells to MNNG.
|ジャーナル||Japanese Journal of Cancer Research|
|出版ステータス||出版済み - 1 1992|
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