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A functional p53-responsive intronic promoter is contained within the human mdm2 gene.

ABSTRACT: The mdm2 gene is a target for transcriptional activation by the p53 tumor suppressor gene product. Previous work has revealed that the mouse mdm2 gene contains two promoters: one is located upstream to the gene and is active in the absence of p53, the other resides within the first intron and requires p53 for transcriptional activity. To determine whether this unique promoter activation pattern is biologically important, we investigated the structure and function of the corresponding region of the human mdm2 (hmdm2) gene. We report here that the hmdm2 gene also contains an intronic, p53-dependent promoter. The structural features of this promoter are highly conserved between mouse and man, as opposed to the lack of conservation of the first exon. This promoter is triggered in vivo in the presence of activated wild type p53, leading to the production of novel mRNA species. The intronic hmdm2 promoter contains two tandem p53 binding elements. Deletion analysis suggests that optimal promoter activity requires the simultaneous binding of p53 to both elements; this may serve to prevent premature triggering of the promoter by p53.

SUBMITTER: Zauberman A

PROVIDER: S-EPMC307078 | biostudies-other | 1995 Jul

REPOSITORIES: biostudies-other

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A functional p53-responsive intronic promoter is contained within the human mdm2 gene.

Zauberman A A Flusberg D D Haupt Y Y Barak Y Y Oren M M

Nucleic acids research 19950701 14

The mdm2 gene is a target for transcriptional activation by the p53 tumor suppressor gene product. Previous work has revealed that the mouse mdm2 gene contains two promoters: one is located upstream to the gene and is active in the absence of p53, the other resides within the first intron and requires p53 for transcriptional activity. To determine whether this unique promoter activation pattern is biologically important, we investigated the structure and function of the corresponding region of t ...[more]

PMID: 7651818

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Project description:BackgroundUrinary bladder carcinoma stage T1 is an unpredictable disease that in some cases has a good prognosis with only local or no recurrence, but in others can appear as a more aggressive tumor with progression to more advanced stages. The aim here was to investigate stage T1 tumors regarding MDM2 promoter SNP309 polymorphism, mutations in the p53 gene, and expression of p53 and p16 measured by immunohistochemistry, and subsequently relate these changes to tumor recurrence and progression. We examined a cohort of patients with primary stage T1 urothelial carcinoma of the bladder and their tumors.MethodsAfter re-evaluation of the original slides and exclusions, the study population comprised 141 patients, all with primary stage T1 urothelial carcinoma of the bladder. The hospital records were screened for clinical parameters and information concerning presence of histologically proven recurrence and progression. The paraffin-embedded tumor material was evaluated by immunohistochemistry. Any mutations found in the p53 gene were studied by single-strand conformation analysis and Sanger sequencing. The MDM2 SNP309 polymorphism was investigated by pyrosequencing. Multivariate analyses concerning association with prognosis were performed, and Kaplan-Meier analysis was conducted for a combination of changes and time to progression.ResultsOf the 141 patients, 82 had at least one MDM2 SNP309 G allele, and 53 had a mutation in the p53 gene, but neither of those anomalies was associated with a worse prognosis. A mutation in the p53 gene was associated with immunohistochemically visualized p53 protein expression at a cut-off value of 50%. In the group with p53 mutation Kaplan-Meier analysis showed higher rate of progression and shorter time to progression in patients with immunohistochemically abnormal p16 expression compared to them with normal p16 expression (p = 0.038).ConclusionsMDM2 SNP309 promoter polymorphism and mutations in p53 were not associated with worse prognosis in this cohort of patients with primary stage T1 urinary bladder carcinoma. However, patients with abnormal p16 expression and a mutated p53 gene had a higher rate of and a shorter time to progression, and p53 gene mutation was associated with an abnormal immunohistochemistry for p53 at a cut-off of 50%.

Dataset Information

A functional p53-responsive intronic promoter is contained within the human mdm2 gene.

Publications

A functional p53-responsive intronic promoter is contained within the human mdm2 gene.

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