Marcel, V., Fernandes, K., Terrier, O. et al. Modulation of p53β and p53γ expression by regulating the alternative splicing of TP53 gene modifies cellular response. Cell Death Differ 21, 1377–1387 (2014). https://doi.org/10.1038/cdd.2014.73
Abstract:
In addition to the tumor suppressor p53 protein, also termed p53a, the TP53 gene produces p53b and p53c through alternative splicing of exons 9b and 9c located within TP53 intron 9. Here we report that both TG003, a specific inhibitor of Cdc2-like kinases (Clk) that regulates the alternative splicing pre-mRNA pathway, and knockdown of SFRS1 increase expression of endogenous p53b and p53c at mRNA and protein levels. Development of a TP53 intron 9 minigene shows that TG003 treatment and knockdown of SFRS1 promote inclusion of TP53 exons 9b/9c. In a series of 85 primary breast tumors, a significant association was observed between expression of SFRS1 and a variant, supporting our experimental data. Using siRNA specifically targeting exons 9b/9c, we demonstrate that cell growth can be driven by modulating p53b and p53c expression in an opposite manner, depending on the cellular context. In MCF7 cells, p53b and p53c promote apoptosis, thus inhibiting cell growth. By transient transfection, we show that p53b enhanced p53a transcriptional activity on the p21 and Bax promoters, while p53c increased p53a transcriptional activity on the Bax promoter only. Moreover, p53b and p53c co-immunoprecipitate with p53a only in the presence of p53-responsive promoter. Interestingly, although p53b and p53c promote apoptosis in MCF7 cells, p53b and p53c maintain cell growth in response to TG003 in a p53a-dependent manner. The dual activities of p53b and p53c isoforms observed in non-treated and TG003-treated cells may result from the impact of TG003 on both expression and activities of p53 isoforms. Overall, our data suggest that p53b and p53c regulate cellular response to modulation of alternative splicing pre-mRNA pathway by a small drug inhibitor. The development of novel drugs targeting alternative splicing process could be used as a novel therapeutic approach in human cancers.
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Funding Info:
We thank Valerie Meuray and Nadine Schmidt for technical support. VM and KF were supported by Breast Cancer Campaign (grant number: 2010NovPR50); OT was supported by Cancer Research UK. J-CB is a
fellow of Breast Cancer Campaign (grant number: 2012MaySF127). This project was founded by Cancer Research UK (grant number: C8/A6613) to DPL and J-CB, and by Breast Cancer Campaign (grant number: 2010NovPR50) to J-CB.
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The full paper is available for download at the publisher's URL: https://doi.org/10.1038/cdd.2014.73