Project description:Recently global gene expression profiling of patients samples lead to a molecular definition of Burkitt Lymphoma (BL) with lymphocyte enhancer-binding factor 1 (LEF1) as a signature gene. Here we report the discovery of nucleic LEF1 in a very high proportion of BL cases (15/18) and LEF1 target genes. Germinal center B cells were devoid of detectable nuclear LEF1 expression as mantle cell lymphoma (0/5), marginal zone lymphoma (0/6), follicular lymphoma (0/12) or diffuse large B cell lymphoma (DLBCL) (1/31). Using whole genome gene expression profiling after transient knockdown of LEF1 in BL cell lines, new LEF1 target genes were identified. The joint expression of these genes in primary BL samples shows that LEF1 is not only expressed aberrantly in BL but also transcriptionally active. Our study identified aberrantly expressed LEF1 and its target genes suggesting an important functional role in BLs. 3 biological replicates scrb siRNA vs LEF1 si RNA , 4 siRNA are pooled
Project description:Recently global gene expression profiling of patients samples lead to a molecular definition of Burkitt Lymphoma (BL) with lymphocyte enhancer-binding factor 1 (LEF1) as a signature gene. Here we report the discovery of nucleic LEF1 in a very high proportion of BL cases (15/18) and LEF1 target genes. Germinal center B cells were devoid of detectable nuclear LEF1 expression as mantle cell lymphoma (0/5), marginal zone lymphoma (0/6), follicular lymphoma (0/12) or diffuse large B cell lymphoma (DLBCL) (1/31). Using whole genome gene expression profiling after transient knockdown of LEF1 in BL cell lines, new LEF1 target genes were identified. The joint expression of these genes in primary BL samples shows that LEF1 is not only expressed aberrantly in BL but also transcriptionally active. Our study identified aberrantly expressed LEF1 and its target genes suggesting an important functional role in BLs.
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.