Project description:The p53 tumor suppressor belongs to a gene family that includes two other structurally and functionally related members: p63 and p73. However, the regulation of p53 activity differs significantly from that of p73 and p63. To enhance the tumor suppressive activity of p53, we created a p63/p53 hybrid molecule, named p63-53O, which comprises the transcriptional activation and DNA-binding domains of TAp63? and the oligomerization domain of p53. In this study, we generated a series of p63-53O derivatives and developed an advanced hybrid molecule named “Super Hybrid p53 (SHp53).” SHp53 efficiently transactivated several proapoptotic genes, including CASP10, KCNK3, and PYCARD, compared with p53. Moreover, the silencing of these proapoptotic genes partially abolished the apoptotic response to SHp53 in human cancer cells. The potency of SHp53 for suppressing tumorigenesis was also evaluated using in vivo models. Thus, our results identify a better p63/p53 hybrid molecule for the development of anti-cancer therapies. HuH-7 human hepatocellular carcinoma cells were either transduced with adenoviral vectors expressing p53, TAp63gamma, p53-p63 hybrid (super hybrid p53 version 2, p63-53O-FL), or lacZ. After 24 hours, total RNA was isolated and analyzed by hybridization to Agilent-028004 SurePrint G3 Human GE 8x60K Microarray.
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.