Cell-type, Dose, and Mutation-type Specificity Dictate Mutant p53 Functions In Vivo

SummaryThe specific roles of mutant p53's dominant-negative (DN) or gain-of-function (GOF) properties in regulating acute response and long-term tumorigenesis is unclear. Using “knockin” mouse strains expressing varying R246S mutant levels, we show that the DN effect on transactivation is universally observed after acute p53 activation, whereas the effect on cellular outcome is cell-type specific. Reducing mutant p53 levels abrogated the DN effect. Mutant p53's DN effect protected against radiation-induced death but did not accentuate tumorigenesis. Furthermore, the R246S mutant did not promote tumorigenesis compared to p53−/− mice in various models, even when MDM2 is absent, unlike the R172H mutant. Together, these data demonstrate that mutant p53's DN property only affects acute responses, whereas GOF is not universal, being mutation-type specific

Characterization of Novel and Uncharacterized p53 SNPs in the Chinese Population – Intron 2 SNP Co-Segregates with the Common Codon 72 Polymorphism

Multiple single nucleotide polymorphisms (SNPs) have been identified in the tumor suppressor gene p53, though the relevance of many of them is unclear. Some of them are also differentially distributed in various ethnic populations, suggesting selective functionality. We have therefore sequenced all exons and flanking regions of p53 from the Singaporean Chinese population and report here the characterization of some novel and uncharacterized SNPs - four in intron 1 (nucleotide positions 8759/10361/10506/11130), three in intron 3 (11968/11969/11974) and two in the 3′UTR (19168/19514). Allelic frequencies were determined for all these and some known SNPs, and were compared in a limited scale to leukemia and lung cancer patient samples. Intron 2 (11827) and 7 (14181/14201) SNPs were found to have a high minor allele frequency of between 26–47%, in contrast to the lower frequencies found in the US population, but similar in trend to the codon 72 polymorphism (SNP12139) that shows a distribution pattern correlative with latitude. Several of the SNPs were linked, such as those in introns 1, 3 and 7. Most interestingly, we noticed the co-segregation of the intron 2 and the codon 72 SNPs, the latter which has been shown to be expressed in an allele-specific manner, suggesting possible regulatory cross-talk. Association analysis indicated that the T/G alleles in both the co-segregating intron 7 SNPs and a 4tagSNP haplotype was strongly associated increased susceptibility to lung cancer in non-smoker females [OR: 1.97 (1.32, 3.394)]. These data together demonstrate high SNP diversity in p53 gene between different populations, highlighting ethnicity-based differences, and their association with cancer risk

Detection of mutations and polymorphisms in the human B-globin gene and hepatitis B virus precore region by denaturing gradient gel electrophoresis (DGGE)

DNA carries biological information in a form that must be precisely copied and transmitted to all progeny cells. Occasionally, changes in the sequence of a gene may occur during the replication process. These ''genetic mistakes"' are known as mutations. Mutations can be identified by physical, chemical or enzymatic means. In this study, mutations in the human (3-globin gene and HBV pre-core gene were used to evaluate the sensitivity of Denaturing Gradiënt Gel Electrophoresis (DGGE). DNA sequencing was then performed to verify and confirm the unknown mutations in the human p-g!obin gene as well as the HBV pre-core gene.Master of Scienc

Primers used and PCR conditions for sequencing <i>p53.</i>

<p>Primers used and PCR conditions for sequencing <i>p53.</i></p

Kaplan-Meier curves of overall survival of lung cancer patients with different genotypes at intron 7, SNP14181 (A) or SNP14201 (B).

<p>Kaplan-Meier curves of overall survival of lung cancer patients with different genotypes at intron 7, SNP14181 (A) or SNP14201 (B).</p

Four marker haplotype frequencies and association with lung cancer.

<p>Four marker haplotype frequencies and association with lung cancer.</p

Risk estimates (OR^* and 95% CI^#) for leukemia for individual SNP.

<p>*: OR – Odds ratio.</p>#<p>: CI - confidence interval.</p

Graph showing pairwise r² linkage disequilibrium (LD). Squares in red with no numerical indicates complete LD between markers.

<p>Graph showing pairwise r² linkage disequilibrium (LD). Squares in red with no numerical indicates complete LD between markers.</p