p53 is activated in response to disruption of the pre-mRNA splicing machinery

Abstract

In this study, we show that interfering with the splicing machinery results in activation of the tumour-suppressor p53. The spliceosome was targeted by small interfering RNA-mediated knockdown of proteins associated with different small nuclear ribonucleoprotein complexes and by using the small-molecule splicing modulator TG003. These interventions cause: the accumulation of p53, an increase in p53 transcriptional activity and can result in p53-dependent G(1) cell cycle arrest. Mdm2 and MdmX are two key repressors of p53. We show that a decrease in MdmX protein level contributes to p53 activation in response to targeting the spliceosome. Interfering with the spliceosome also causes an increase in the rate of degradation of Mdm2. Alterations in splicing are linked with tumour development. There are frequently global changes in splicing in cancer. Our study suggests that p53 activation could participate in protection against potential tumour-promoting defects in the spliceosome. A number of known p53-activating agents affect the splicing machinery and this could contribute to their ability to upregulate p53. Preclinical studies indicate that tumours can be more sensitive than normal cells to small-molecule spliceosome inhibitors. Activation of p53 could influence the selective anti-tumour activity of this therapeutic approach.

Modulation of p53β and p53γ expression by regulating the alternative splicing of TP53 gene modifies cellular response

“…We recently reported that alteration of alternative splicing pathway activates p53, regulates p53-target gene expression and induces a p53-dependent G1 cell cycle arrest in HCT116 cells. 14 Here we determined whether combined knockdown of p53b and p53g by siP53-i9 affects MCF7 cell response to Figure 6). To exclude difference between siCT and siP53-i9-transfected cells due to variation in basal apoptosis, MTT assays were normalized at the day of TG003 addition ( Figure 6b).…”

“…However, the impact of TG003 on p53a protein is cell line-dependent, p53a expression being either increased or decreased, supporting a cell typedependent effect of TG003. 14 Early studies reported that p53b has some tumor suppressor-like activity in non-treated normal fibroblasts and cancer cells, p53b promoting apoptosis and senescence by differentially regulating gene expression. 3,6 Consistently, endogenous p53b and p53g expression promotes G1 cell cycle arrest and basal apoptosis in MCF7 cells.…”

“…Moreover, TG003 has been shown to modulate alternative splicing in vitro and in vivo, 12,13 and to activate p53 inducing a p53-mediated cell response. 14 Here we investigated the effects of TG003 and SFRS1 on splicing of TP53 intron 9 and characterized the biological consequences.…”

Coherence between Cellular Responses and in Vitro Splicing Inhibition for the Anti-tumor Drug Pladienolide B and Its Analogs

“…Nuclear speckles are cellular bodies that contain transcription and pre-mRNA processing components (24). Knockdown of PB target SF3B1 causes a "mega-speckles" phenotype in which the speckles coalesce into large bodies (25). PB treatment of cells also induces formation of mega-speckles (8).…”

Quantitative proteomic analyses of mammary organoids reveals distinct signatures after exposure to environmental chemicals

“…We found altered expression of the regulators serine/arginine-rich splicing factor 3 (SRSF3), splicing factor 3A3 (SF3A3), heterogeneous nuclear ribonuclear proteins Q and A1, small nuclear ribonuclear proteins A′ and E, regulation of nuclear pre-mRNA domain-containing protein 2 (RPRD2), RNA-binding proteins 22, 4b, 39, 47, and MS, and the RNA helicase DHX30 (Table 1). Perturbation of the splicing machinery also can activate the p53 pathway (71,72).…”