Project description:DNA repair genes: Alternative transcription and gene expression at the exon level in response to the DNA damaging agent, ionizing radiation
Project description:Humans are exposed to ionizing radiation (IR) from background radiation, medical treatments, occupational and accidental exposures. IR causes profound changes in transcription. Transcription is a primary process where protein amount and function can be regulated. One aspect of the transcriptional IR response that little is known about on a whole genome basis is alternative transcription. These investigations focus on the response to IR at the exon level in human cells but also at the whole gene level. Whole genome exon arrays were utilized to comprehensively characterize radiation-induced transcriptional expression products in two human cell types, namely EBV-transformed lymphoblast and primary fibroblast cell lines.
Project description:Humans are exposed to ionizing radiation (IR) from background radiation, medical treatments, occupational and accidental exposures. IR causes profound changes in transcription. Transcription is a primary process where protein amount and function can be regulated. One aspect of the transcriptional IR response that little is known about on a whole genome basis is alternative transcription. These investigations focus on the response to IR at the exon level in human cells but also at the whole gene level. Whole genome exon arrays were utilized to comprehensively characterize radiation-induced transcriptional expression products in two human cell types, namely EBV-transformed lymphoblast and primary fibroblast cell lines. 12 human primary fibroblast cell lines and 12 primary lymphoblast cell line samples were used for two doses (0 and 10 Gy) and two time points (0 and 4hr). Additional doses ( 1 Gy, 2 Gy, 5 Gy, and 20 Gy) and time points ( 1hr, 2hr, 8hr, 24hr and 48hr) were assessed in four lymphoblast cell lines and four primary fibroblasts.
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.