Project description:Two-color microarray experiment compariing the profiles of CBP80-associated mRNAs and eIF4E-associated mRNAs in actively translating polysomes.
Project description:eIF4E, the major cap-binding protein, has long been considered limiting for translating the mammalian genome. However, the requirement for eIF4E dose at an organismal level remains unexplored. By generating an Eif4e haploinsufficient mouse, we surprisingly found that 50% reduction in eIF4E, while compatible with normal development and global protein synthesis, significantly impeded cellular transformation and tumorigenesis. Genome-wide translational profiling uncovered a translational program induced by oncogenic transformation and revealed a critical role for eIF4E dose specifically in translating a network of mRNAs enriched for a unique 5’UTR signature. In particular, we demonstrate that eIF4E dose is essential for translating mRNAs regulating reactive oxygen species (ROS) that fuel transformation and cancer cell survival in vivo. Therefore, mammalian cells have evolved surplus eIF4E levels that cancer cells hijack to drive a translational program supporting tumorigenesis Total cellular RNA and high MW polysome associated RNA were isolated from matched untransformed and transformed WT and Eif4e+/- MEFs for analysis on Affymetrix Mouse Gene 1.0 ST arrays. The difference in log2 RMA intensity between matched polysomal RNA and total RNA was taken to quantify translational efficiency (TE).
Project description:eIF4E, the major cap-binding protein, has long been considered limiting for translating the mammalian genome. However, the requirement for eIF4E dose at an organismal level remains unexplored. By generating an Eif4e haploinsufficient mouse, we surprisingly found that 50% reduction in eIF4E, while compatible with normal development and global protein synthesis, significantly impeded cellular transformation and tumorigenesis. Genome-wide translational profiling uncovered a translational program induced by oncogenic transformation and revealed a critical role for eIF4E dose specifically in translating a network of mRNAs enriched for a unique 5’UTR signature. In particular, we demonstrate that eIF4E dose is essential for translating mRNAs regulating reactive oxygen species (ROS) that fuel transformation and cancer cell survival in vivo. Therefore, mammalian cells have evolved surplus eIF4E levels that cancer cells hijack to drive a translational program supporting tumorigenesis
Project description:Deciphering the regulatory network for human naïve and primed pluripotency is of fundamental theoretical and applicable significance. Here, by combining quantitative proteomics, phosphoproteomics and acetylproteomics analyses, we revealed RNA processing and translation as the most differentially-regulated processes between naïve and primed human embryonic stem cells (hESCs). While glycolytic primed hESCs rely predominantly on eIF4E-mediated cap-dependent pathway for protein translation, naïve hESCs with reduced mTORC1 activity are more tolerant to blockage of eIF4E-dependent translation, and their bivalent metabolism allows for translating selective mRNAs via both eIF4E-dependent and eIF4E-independent/eIF4A2-dependent pathways to form a more compact naïve proteome. Globally up-regulated proteostasis system and down-regulated post-translational modification system help to further refine and maintain the naïve proteome that is compatible with the more rapid cycling of naïve hESCs, where CDK1 plays an indispensable coordinative role.
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: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.