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A single-nucleotide variation in a p53-binding site affects nutrient-sensitive human SIRT1 expression.

ABSTRACT: The SIRTUIN1 (SIRT1) deacetylase responds to changes in nutrient availability and regulates mammalian physiology and metabolism. Human and mouse SIRT1 are transcriptionally repressed by p53 via p53 response elements in their proximal promoters. Here, we identify a novel p53-binding sequence in the distal human SIRT1 promoter that is required for nutrient-sensitive SIRT1 transcription. In addition, we show that a common single-nucleotide (C/T) variation in this sequence affects nutrient deprivation-induced SIRT1 transcription, and calorie restriction-induced SIRT1 expression. The p53-binding sequence lies in a region of the SIRT1 promoter that also binds the transcriptional repressor Hypermethylated-In-Cancer-1 (HIC1). Nutrient deprivation increases occupancy by p53, while decreasing occupancy by HIC1, of this region of the promoter. HIC1 and p53 compete with each other for promoter occupancy. In comparison with the T variation, the C variation disrupts the mirror image symmetry of the p53-binding sequence, resulting in decreased binding to p53, decreased nutrient sensitivity of the promoter and impaired calorie restriction-stimulated tissue expression of SIRT1 and SIRT1 target genes AMPK?2 and PGC-1?. Thus, a common SNP in a novel p53-binding sequence in the human SIRT1 promoter affects nutrient-sensitive SIRT1 expression, and could have a significant impact on calorie restriction-induced, SIRT1-mediated, changes in human metabolism and physiology.

SUBMITTER: Naqvi A

PROVIDER: S-EPMC2951863 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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A single-nucleotide variation in a p53-binding site affects nutrient-sensitive human SIRT1 expression.

Naqvi Asma A Hoffman Timothy A TA DeRicco Jeremy J Kumar Ajay A Kim Cuk-Seong CS Jung Saet-Byel SB Yamamori Tohru T Kim Young-Rae YR Mehdi Fardeen F Kumar Santosh S Rankinen Tuomo T Ravussin Eric E Irani Kaikobad K

Human molecular genetics 20100806 21

The SIRTUIN1 (SIRT1) deacetylase responds to changes in nutrient availability and regulates mammalian physiology and metabolism. Human and mouse SIRT1 are transcriptionally repressed by p53 via p53 response elements in their proximal promoters. Here, we identify a novel p53-binding sequence in the distal human SIRT1 promoter that is required for nutrient-sensitive SIRT1 transcription. In addition, we show that a common single-nucleotide (C/T) variation in this sequence affects nutrient deprivati ...[more]

PMID: 20693263

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Project description:UNLABELLED:Multiple lines of evidence suggest regulatory variation to play an important role in phenotypic evolution and disease development, but few regulatory polymorphisms have been characterized genetically and molecularly. Recent technological advances have made it possible to identify bona fide regulatory sequences experimentally on a genome-wide scale and opened the window for the biological interrogation of germ-line polymorphisms within these sequences. In this study, through a forward genetic analysis of bona fide p53 binding sites identified by a genome-wide chromatin immunoprecipitation and sequence analysis, we discovered a SNP (rs1860746) within the motif sequence of a p53 binding site where p53 can function as a regulator of transcription. We found that the minor allele (T) binds p53 poorly and has low transcriptional regulation activity as compared to the major allele (G). Significantly, the homozygosity of the minor allele was found to be associated with an increased risk of ER negative breast cancer (OR = 1.47, P = 0.038) from the analysis of five independent breast cancer samples of European origin consisting of 6,127 breast cancer patients and 5,197 controls. rs1860746 resides in the third intron of the PRKAG2 gene that encodes the ? subunit of the AMPK protein, a major sensor of metabolic stress and a modulator of p53 action. However, this gene does not appear to be regulated by p53 in lymphoblastoid cell lines nor in a cancer cell line. These results suggest that either the rs1860746 locus regulates another gene through distant interactions, or that this locus is in linkage disequilibrium with a second causal mutation. This study shows the feasibility of using genomic scale molecular data to uncover disease associated SNPs, but underscores the complexity of determining the function of regulatory variants in human populations. ELECTRONIC SUPPLEMENTARY MATERIAL:The online version of this article (doi:10.1007/s11568-010-9138-x) contains supplementary material, which is available to authorized users.

Project description:The tp53 gene is found to be mutated in 50% of all the cancers. The p53 protein, a product of tp53 gene, is a multi-domain protein. It consists of a core DNA binding domain (DBD) which is responsible for its binding and transcription of downstream target genes. The mutations in p53 protein are responsible for creating cancerous conditions and are found to be occurring at a high frequency in the DBD region of p53. Some of these mutations are also known to be temperature sensitive (ts) in nature. They are known to exhibit partial or strong binding with DNA in the temperature range (298-306 K). Whereas, at 310 K and above they show complete loss in binding. We have analyzed the changes in binding and conformational behavior at 300 K and 310 K for three of the ts-mutants viz., V143A, R249S and R175H. QM-MM simulations have been performed on the wild type and the above mentioned ts-mutants for 30 ns each. The optimal estimate of free energy of binding for a particular number of interface hydrogen bonds was calculated using the maximum likelihood method as described by Chodera et. al (2007). This parameter has been observed to be able to mimic the binding affinity of the p53 ts-mutants at 300 K and 310 K. Thus the correlation between MM-GBSA free energy of binding and hydrogen bonds formed by the interface residues between p53 and DNA has revealed the temperature dependent nature of these mutants. The role of main chain dihedrals was obtained by performing dihedral principal component analysis (PCA). This analysis, suggests that the conformational variations in the main chain dihedrals (? and ?) of the p53 ts-mutants may have caused reduction in the overall stability of the protein. The solvent exposure of the side chains of the interface residues were found to hamper the binding of the p53 to the DNA. Solvent Accessible Surface Area (SASA) also proved to be a crucial property in distinguishing the conformers obtained at 300 K and 310 K for the three ts-mutants from the wild type at 300 K.

Dataset Information

A single-nucleotide variation in a p53-binding site affects nutrient-sensitive human SIRT1 expression.

Publications

A single-nucleotide variation in a p53-binding site affects nutrient-sensitive human SIRT1 expression.

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