10.20381/ruor-19955
Smith, Jennifer M
Amino-terminal transactivation subdomains of p53 contribute equally to p53-induced gene expression
Université d'Ottawa / University of Ottawa
2009
Biology, Molecular.
Université d'Ottawa / University of Ottawa
Université d'Ottawa / University of Ottawa
2013-11-08
2013-11-08
2009
2009
en
Thesis
Source: Dissertation Abstracts International, Volume: 71-06, Section: B, page: 3484.
http://hdl.handle.net/10393/29877
The p53 tumour suppressor is mutated in over 50% of sporadic cancers. Its tumour suppressive functions arise in large part from transcriptional activation of target genes. Two adjacent regions within the transactivation domain of p53 are sufficient to support sequence-specific transactivation when fused to a heterologous DNA binding domain. It has been hypothesized that these two subdomains of p53 may contribute to the expression of distinct p53-responsive genes and regulate distinct biological pathways. In order to examine the subdomain requirements during transactivation, we used oligonucleotide microarrays to identify transcripts induced by variants of p53 with point mutations within subdomains 1, 2, or both (QS1, QS2, and QS1/QS2, respectively). Expression of wild type p53 (P53WT) statistically induced 254 transcripts and apoptosis transcripts (GO#0006915) were the only statistically over represented group. Most of these transcripts were poorly induced by the p53 variants and there was a corresponding decrease in the ability of these variants to induce apoptosis. Strikingly, several well known p53-regulated transcripts including TNFRSF10B, BTG2, and POLH were increased to wild type levels by p53QS1 and p53QS2 but not p53QS1/QS2, indicating that either subdomain1 or 2 is sufficient for p53-dependent expression of a small subset of p53-responsive genes. Unexpectedly, there was no evidence for p53QS1- or p53 QS2-specific gene expression. Taken together, these results demonstrated heterogeneity in the requirement for transactivation subdomains 1 and 2 of p53 without subdomain-specific contributions to p53-induced gene expression. The MafB transcript was identified as a p53WT -induced transcript that was not statistically increased in response to either p53QS1 or p53QS2 expression. Nonetheless, MafB expression increased more in response to the QS2 compared to the QS1 variant of p53 so MafB was studied further as a potential p53 target gene exhibiting a QS2-specific pattern of expression. Expression of p53WT increased MafB mRNA and protein levels and bound to a putative response element 2400bp upstream of the transcription start site. Expression of p53QS2 consistently increased MafB expression more than p53QS1, however this level did not approach the expression of MafB induced by p53WT. Therefore, MafB represents a novel p53-regulated transcript that is poorly induced by both p53QS1 and p53QS2.