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Differential regulation of P53 and Bcl-2 expression by ultraviolet A and B
Y Wang1, B Rosenstein, S Goldwyn
1Department of Dermatology, Mount Sinai School of Medicine, New York, New York 10029, USA.
Abstract:
The induction of apoptosis by ultraviolet (UV) radiation and other DNA damaging agents plays a critical role in monitoring the accumulation of genetic damage and the suppression of tumor development. We hypothesize that UVA and UVB induce apoptosis by modulating balances between p53 and/or bcl-2 genes. Using MCF-7 cells that express both wild-type P53 and Bcl-2 proteins, we demonstrated that UVA and UVB induced apoptosis through regulating expression of apoptosis promoting or inhibiting genes. UVA induced immediate apoptosis and downregulated bcl-2 expression. Bcl-2 expression was reduced by approximately 40% at 4 h post-150 kJ UVA irradiation per m2 with a maximum downregulation (over 70%) at 24 h. The dose-response studies revealed that significant reduction of bcl-2 expression was observed at UVA doses ranging from 50 to 200 kJ per m2; however, p53 levels were not affected by UVA. In contrast, UVB exhibited a entirely different action than UVA in that UVB substantially induced p53 expression, but had no effect on bcl-2 expression. The induction of P53 by UVB was dose and time dependent with the maximum expression at 24 h post-2 and post-4 kJ UVB irradiation per m2. Down-regulation of bcl-2 and fragmentation of DNA induced by UVA occurred earlier (approximately at 4 h) than upregulation of p53 and DNA fragmentation by UVB (12-24 h). These results suggest that UVA and UVB cause cell damage through different mechanisms and that the balances between the expression of p53 and bcl-2 may play an important role in regulating the apoptosis induced by UV irradiation.
Insights
Ultraviolet (UV) radiation induces apoptosis differently; UVA downregulates Bcl-2, while UVB upregulates p53. Both UV types damage DNA, highlighting distinct mechanisms in cell death regulation.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Apoptosis, or programmed cell death, is crucial for preventing tumor development by eliminating cells with genetic damage.
- Understanding the molecular mechanisms of UV-induced apoptosis is vital for cancer research and prevention strategies.
Purpose of the Study:
- To investigate the distinct roles of UVA and UVB radiation in inducing apoptosis.
- To determine the involvement of p53 and Bcl-2 gene expression in UV-mediated apoptosis.
Main Methods:
- Utilized MCF-7 cells expressing wild-type p53 and Bcl-2 proteins.
- Exposed cells to varying doses and durations of UVA and UVB radiation.
- Monitored apoptosis, DNA fragmentation, and the expression levels of p53 and Bcl-2 proteins.
Main Results:
- UVA radiation induced apoptosis earlier, downregulating Bcl-2 expression significantly without affecting p53 levels.
- UVB radiation induced p53 expression in a dose- and time-dependent manner, with no effect on Bcl-2.
- DNA fragmentation occurred earlier with UVA compared to UVB, which also induced p53 upregulation.
Conclusions:
- UVA and UVB radiation trigger apoptosis through distinct molecular pathways.
- The balance between p53 and Bcl-2 gene expression is a key regulator of UV-induced apoptosis.
- Differential modulation of apoptosis-related genes by UVA and UVB contributes to varied cellular responses to DNA damage.