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Suppression of UV-induced mutations by wild-type p53 protein in human osteosarcoma cells
N Yamagishi1, J Miyakoshi, T Yagi
1Department of Radiation Genetics, Faculty of Medicine, Kyoto University, Yoshida-konoecho, Sakyo-ku, Japan.
Abstract:
We have examined whether the tumour suppressor p53 protein suppressed UV-induced mutations in the hypoxathine-guanine phosphoribosyl transferase (HPRT) gene and in the supF gene of the shuttle vector plasmid pMY189. We used human osteosarcoma Saos-LP12 cells, in which wild type (wt) p53 protein was induced by treatment with isopopyl-beta-D-thiogalactopyranoside. The induction of wt p53 protein suppressed UV-induced mutations but not spontaneous mutations in the HPRT gene. The frequency of UV-induced mutations induced by UV-irradiation of the plasmid was also significantly lower in cells with induced wt p53 protein than in the uninduced cells. In addition, we found that frequency of G : C to A : T transition mutations which occurred at the 3' base pair of dipyrimidine sites were significantly lower in the cells with induced wt p53 protein than in the uninduced cells. These findings suggest that wt p53 protein may play roles in modulating DNA repair pathway, resulting in the suppression of UV-induced mutations.
Insights
The tumor suppressor p53 protein was found to suppress UV-induced mutations in human cells. This suggests wild-type p53 plays a role in DNA repair, reducing DNA damage from UV radiation.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- The tumor suppressor p53 protein is crucial in cellular responses to DNA damage.
- UV radiation is a known mutagenic agent that can lead to DNA damage and mutations.
- Understanding p53's role in DNA repair is vital for cancer prevention and treatment.
Purpose of the Study:
- To investigate the effect of wild-type p53 protein on UV-induced mutations in the HPRT and supF genes.
- To determine if p53 influences spontaneous mutations or mutations induced by UV irradiation of cellular DNA or plasmid DNA.
Main Methods:
- Utilized human osteosarcoma Saos-LP12 cells with inducible wild-type p53.
- Assessed mutations in the hypoxathine-guanine phosphoribosyl transferase (HPRT) gene and the supF gene of the pMY189 shuttle vector plasmid.
- Quantified spontaneous and UV-induced mutations in the presence and absence of induced wild-type p53.
Main Results:
- Induced wild-type p53 significantly suppressed UV-induced mutations in the HPRT gene.
- Wild-type p53 did not suppress spontaneous mutations in the HPRT gene.
- UV-induced mutations in plasmid DNA were significantly lower in cells with induced wild-type p53.
- G:C to A:T transition mutations at dipyrimidine sites were reduced by induced wild-type p53.
Conclusions:
- Wild-type p53 protein suppresses UV-induced mutations, indicating a role in DNA repair modulation.
- p53's protective effect is specific to UV-induced DNA damage, not spontaneous mutations.
- These findings highlight p53's importance in cellular defense against UV-induced genetic alterations.