Carcinogenesis, Vol 18, 695-700, Copyright © 1997 by Oxford University Press
N Yamagishi, J Miyakoshi and H Takebe
Tumor suppressor p53 protein acts as a checkpoint factor following DNA
damage. Inactivation of checkpoint control may increase the frequency of
mutation following DNA damage, resulting in tumor progression. Here we
examine whether wild-type (wt) p53 protein suppresses X-ray-induced
mutations using an isopropyl-beta-D-thiogalactopyranoside (IPTG)- regulated
p53 expression system in human osteosarcoma Saos-2 cells. Frequency of
X-ray-induced mutations in the hypoxanthine-guanine phosphoribosyl
transferase gene was enhanced about 10 and 20 times by 1 and 2 Gy
respectively in cells without expression of wt p53 protein, while
enhancement of mutations by X-rays was slight in cells with expression of
wt p53 protein. Furthermore, arrest at the G/S boundary was induced by
X-ray irradiation when p53 protein was expressed by treatment with IPTG.
These findings suggest that wt p53 protein has a function in maintaining
genomic stability after X-ray irradiation through the G1 checkpoint and
loss of p53 function(s) may lead to tumor progression in multi-step
tumorigenesis.
ARTICLES
Decrease in the frequency of X-ray-induced mutation by wild-type p53 protein in human osteosarcoma cells
Department of Radiation Genetics, Faculty of Medicine, Kyoto University, Sakyo-ku, Japan.
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