Project description:To develop a more complete characterization of TFAP2C target genes, ChIP-seq with anti-TFAP2C antibody and expression arrays with TFAP2C knock down were analyzed in MCF-7 breast carcinoma cells. To find TFAP2C binding sites
Project description:The complexity of gene regulation has created obstacles to defining mechanisms that establish the patterns of gene expression characteristic of the different clinical phenotypes of breast cancer. Transcription factor TFAP2C plays a critical role in the regulation of both estrogen receptor-alpha (ERM-NM-1) and c-ErbB2/HER2 (Her2). Herein, we performed chromatin immunoprecipitation and direct sequencing (ChIP-seq) for TFAP2C in four breast cancer cell lines representing different clinical phenotypes. Comparing the genomic binding sites for TFAP2C in the various cell lines, we identified that glutathione peroxidase (GPX1) is regulated by TFAP2C through an AP-2 regulatory region in the promoter of the GPX1 gene. Knock-down of TFAP2C, but not the related factor TFAP2A, resulted in an abrogation of GPX1 expression. Selenium-dependent GPX activity correlated with endogenous GPX1 expression, and overexpression of exogenous GPX1 induced GPX activity and significantly increased resistance to tert-butyl hydroperoxide. Methylation of the CpG island encompassing the AP-2 regulatory region was identified in cell lines where TFAP2C failed to bind the GPX1 promoter and GPX1 expression was unresponsive to TFAP2C. Furthermore, in cell lines where GPX1 promoter methylation was associated with gene silencing, treatment with 5-aza-dC (an inhibitor of DNA methylation) resulted in activation of GPX1 RNA and protein expression. Methylation of the GPX1 promoter was identified in approximately 20% of primary breast cancers and a highly significant correlation between TFAP2C and GPX1 expression was confirmed when considering only those tumors with an unmethylated promoter, whereas the related factor, TFAP2A, failed to demonstrate a correlation. The results demonstrate that TFAP2C regulates the expression of GPX1, which influences the redox state and sensitivity to oxidative stress induced by peroxides. Given the established role of GPX1 in breast cancer, the results provide an important mechanism for TFAP2C to further influence oncogenesis and progression of breast carcinoma cells. 4 ChIP-Seq data for TFAP2C in human breast carcinoma cell lines MCF-7, BT-474, MDA-MB-453 and SKBR-3.
Project description:To develop a more complete characterization of TFAP2C target genes, ChIP-seq with anti-TFAP2C antibody and expression arrays with TFAP2C knock down were analyzed in MCF-7 breast carcinoma cells.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:Estrogen Receptor alpha (ERα) is a ligand-inducible transcription factor that mediates estrogen signaling in hormone-responsive breast cancer (BC) and is the primary target of specific anticancer therapies. Although ERα blockade with these drugs is effective, the development of a resistance to treatment represents the key problem in clinical management of patients affected by this disease. Understanding the molecular mechanisms underlying ERα action in BC cells may help the identification of new therapeutic targets for more effective pharmacological treatment of endocrine therapy-resistant tumors. We recently discovered the epigenetic enzyme DOT1L (DOT1 Like Histone Lysine Methyltransferase) as a novel nuclear partner of ERα in BC cells. To investigate the involvement of DOT1L in mediating ERα actions in hormone-responsive and endocrine-resistant BC, physical and functional interaction between these two molecules on chromatin was mapped by Chromatin Immunoprecipitation coupled to Mass Spectrometry (ChIP-MS).
Project description:Estrogen Receptor alpha (ERα) is a ligand-inducible transcription factor that mediates estrogen signaling in hormone-responsive breast cancer (BC) and is the primary target of specific anticancer therapies that although effective can generate resistance phenomena that represents a crucial problem in clinical management of patients affected by this disease. DOT1 Like Histone Lysine Methyltransferase (DOT1L) and Menin 1 (MEN1) have been identified as functional component of the ERα mechanism of action. To investigate the involvement of DOT1L and MEN1 in mediating ERα actions in hormone-responsive and endocrine-resistant BC, interaction proteomics was applied to map the DOT1l and MEN1 nuclear interacting partners in MCF7 breast cancer cell nuclei in order to the identifiy new possible therapeutic targets for a more effective pharmacological treatment of endocrine therapy-resistant tumors.
Project description:This study is an attempt to characterize the molecular basis for the functional differences between TFAP2A and TFAP2C. Recent findings have highlighted a critical role for the TFAP2C (AP-2M-NM-3) transcription factor in maintaining the luminal phenotype through the regulation of luminal-associated genes. Of particular interest is that the highly homologous AP-2 family member, TFAP2A (AP-2M-NM-1), is expressed in luminal breast cancer but appears to have a functionally distinct role in gene regulation. There is 83% similarity between TFAP2A and TFAP2C with 76% identity in the carboxyl-half of the proteins containing the DNA binding and dimerization domains. Although the two family members appear to have complementary and overlapping roles in regulating neural crest development, they have clear functional differences with regard to regulation of ERM-NM-1 expression. The global genomic binding pattern for TFAP2A and TFAP2C is highly similar. Genomic binding for TFAP2A and TFAP2C in the regulatory region for luminal-associated genes further demonstrated co-localization of the two factors. On the other hand, clear functional differences exist when comparing the effect on the pattern of gene expression following knockdown of TFAP2A vs. TFAP2C. In each case, knockdown of TFAP2C resulted in an abrogation of expression (RNA and protein) of the luminal-associated gene, whereas, knockdown of TFAP2A had minimal or no effect. By contrast, a known TFAP2A target gene, CDKN1A, was responsive to TFAP2A only. 1 ChIP-Seq data for TFAP2A in human breast carcinoma cell line MCF-7. See associated publication.
Project description:As the evolution of miRNA genes has been found to be one of the important factors in formation of the modern type of man, we performed a comparative analysis of the evolution of miRNA genes in two archaic hominines, Homo sapiens neanderthalensis and Homo sapiens denisova, and elucidated the expression of their target mRNAs in bain.A comparative analysis of the genomes of primates, including species in the genus Homo, identified a group of miRNA genes having fixed substitutions with important implications for the evolution of Homo sapiens neanderthalensis and Homo sapiens denisova. The mRNAs targeted by miRNAs with mutations specific for Homo sapiens denisova exhibited enhanced expression during postnatal brain development in modern humans. By contrast, the expression of mRNAs targeted by miRNAs bearing variations specific for Homo sapiens neanderthalensis was shown to be enhanced in prenatal brain development.Our results highlight the importance of changes in miRNA gene sequences in the course of Homo sapiens denisova and Homo sapiens neanderthalensis evolution. The genetic alterations of miRNAs regulating the spatiotemporal expression of multiple genes in the prenatal and postnatal brain may contribute to the progressive evolution of brain function, which is consistent with the observations of fine technical and typological properties of tools and decorative items reported from archaeological Denisovan sites. The data also suggest that differential spatial-temporal regulation of gene products promoted by the subspecies-specific mutations in the miRNA genes might have occurred in the brains of Homo sapiens denisova and Homo sapiens neanderthalensis, potentially contributing to the cultural differences between these two archaic hominines.