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Tesi etd-03012009-234910

Thesis type
Tesi di dottorato di ricerca
TP53 isoforms and effect of genetic polymorphisms on the internal promoter activity
Settore scientifico disciplinare
Corso di studi
Relatore Landi, Stefano
Parole chiave
  • isoform
  • internal promoter
  • polymorphism
Data inizio appello
Data di rilascio
Riassunto analitico
P53 tumour suppressor protein plays a key role in maintaining genomic integrity. For 25 years, the p53 was considered the only protein expressed by TP53 gene. Since 2002, several groups have identified and described the existence of up to 10 p53 isoforms. It is now clear that the patterns of p53 expression are much more complex than previously recognized and that these isoforms have the potential to act either synergistically or antagonistically, depending on their structure and mechanism of production. This thesis focuses on the ΔNp53 Isoforms Δ133p53 and Δ40p53 to elucidate their specific properties on p53 suppressive activity as well as their expression in different normal and tumour tissues. We confirmed that ΔNp53 are dominant-negative toward full-length p53 (FL-p53) inhibiting p53-mediated apoptosis, thereby modulating the FL-p53 transcriptional activity and the cell fate outcome in response to stress. Moreover, isoform ΔN133p53 is produced by an internal promoter region (IPR) encompassing introns three and four. Interestingly, case-control studies showed that some polymorphisms within the IPR are associated with the susceptibility to several types of cancer. We sequenced the IPR in 47 human cell lines and eight polymorphisms were found (-/PIN3; IVS3 -29C>A; Pro36Pro; Arg72Pro; IVS4 -283C>T; IVS4 -125T>C; IVS4 -117A>G, IVS4 -91A>G). The haplotypes were reconstructed and their functional effect was examined with a reporter gene expression assay transfecting HeLa and 293T human cell lines. Our study suggests a role for the different haplotypes of the IPR in affecting the expression of the Δ133p53 isoform in both these types of cells. Quantitative PCR experiments performed on human normal tissues appeared to confirm the findings obtained in vitro. These results could help to explain the regulation of Δ133p53 expression and why some polymorphisms in TP53 are associated with the risk of cancer for humans.