ΔN133p53 expression levels in relation to haplotypes of the TP53 internal promoter region

Abstract

The transcription of the DeltaN133p53 isoform of the TP53 gene is controlled by an internal promoter region (IPR) containing eight polymorphisms in 11 common haplotypes, following a resequencing of 47 Caucasians. We assayed the functional effects of the commonest six haplotypes on the promoter activity with a luciferase reporter system, in HeLa and 293T cells. These studies showed that different IPR haplotypes are associated with differences in the promoter activity resulting in marked variation in the baseline expression of DeltaN133p53. In vivo quantitative-polymerase chain reaction (PCR) on human tissues confirmed that the baseline levels of DeltaN133p53 showed haplotype specific differences that paralleled those seen in vitro. When cell lines were treated with camptothecin, the fold-increase in DeltaN133p53 levels was dose-dependent but haplotype-independent (i.e., similar for all the haplotypes). Finally, we used an electrophoretic mobility shift assay to analyze the rs1794287 polymorphism and found changes in the pattern of protein binding. This partially confirmed our in silico analysis showing that the polymorphism rs1794287 can affect the function of the internal promoter by changing its affinity for several transcription factors. Thus, we showed that the expression of DeltaN133p53 is under genetic control, and suggested the presence of interindividual differences underlying this mechanism.

Diverse p63 and p73 isoforms regulate Δ133p53 expression through modulation of the internal TP53 promoter activity

“…21,22 We confirmed that D133p53 expression is under genetic control as reported by Bellini et al, 23 because constructs carrying A2-R and A1-P haplotypes had a stronger and significantly higher intrinsic luciferase activity than that of A1-R and A2-P haplotypes (Figure 4d). Although no difference was observed for p53a, p63b, DNp63a and DNp63b, these two polymorphisms modulate the DNp73g-mediated transactivation (Figure 4e).…”

“…17 Interestingly, the DNp73g-mediated transactivation is altered by the polymorphisms TP53 PIN3 and PEX4 (codon 72/R72P), which affect the basal activity of the internal TP53 promoter as already described. 23 This suggests a cooperation between DNp73g and another transcription factor that is able to bind to the response elements encompassing those two SNPs, such as ZNF143, known to interact with p73 protein, 33 and for which several predicted binding sites are overlapping with PIN3. 34 For p63b, we observed that p53RE-A1/A2 is not essential, whereas the region 753-1042 is required to obtain the maximal p63b-mediated transactivation.…”

Δ133p53 is an independent prognostic marker in p53 mutant advanced serous ovarian cancer

“…A possible explanation for differing Δ133p53 levels in cancer specimens observed in the present study might be provided by the presence of several polymorphisms within the internal promoter region located in the intron 4 of the p53 gene, which gives rise to Δ133p53 (Bellini et al , 2010). Bellini et al (2010) reported that these polymorphisms are associated with differences in promoter activity by changing the affinity for distinct transcription factors.…”

“…Bellini et al (2010) reported that these polymorphisms are associated with differences in promoter activity by changing the affinity for distinct transcription factors.…”

ΔNp63 mediates cellular survival and metastasis in canine osteosarcoma

“…For example, it is possible that polymorphisms within the internal promoter region of p63 contribute to high expression of ΔNp63 in canine OSA, thereby promoting a more aggressive biologic behavior. In support of this possibility, it was recently demonstrated that interindividual differences in internal promoter region haplotypes influence baseline Δ133p53 expression, and that polymorphisms within the internal promoter of the p53 gene drive the overexpression of Δ133p53, an oncogenic isoform of that gene [40]. Interestingly, STAT3 is constitutively phosphorylated in many cancers including canine and human OSA [41].…”