Project description:We performed a CRISPR-based functional genetic screen targeting TEAD4 binding motif located within the YAP-bound enhancers. The screen identified seven functional enhancers whose targeting resulted in a marked negative effect on the proliferation of MCF10A-YAP-5SA cells (overexpressed constrictively activated YAP) but no significant effect on MCF10A (parental control) cells. We then carried out RNA-seq analysis on MCF10A-YAP-5SA cells transduced with sgRNA vectors targeting these seven enhancers (enhancers A, B, C, D, E, F, G) as well as the non-targeting sgRNA as control (NT).
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:Cardiomyocyte (CM) loss after injury results in adverse remodelling and fibrosis, which inevitably lead to heart failure. Neuregulin-ErbB2 and Hippo-Yap signaling pathways are key mediators of CM proliferation and regeneration although the crosstalk between these pathways is unclear. Here, we demonstrate in mice that temporal over-expression (OE) of activated ErbB2 in CMs promotes cardiac regeneration in a heart failure model. Cellularly, OE CMs present an EMT-like regenerative response involving cytoskeletal reprograming, migration, ECM turnover, and displacement. Molecularly, we identified Yap as a critical mediator of ErbB2 signaling. In OE CMs, Yap interacts with nuclear envelope and cytoskeletal components, reflective of the altered mechanic state elicited by ErbB2. Hippo-independent activating phosphorylation on Yap at S352 and S274 were enriched in OE CMs, peaking during metaphase. Viral overexpression of Yap phospho-mutants dampened the proliferative competence of OE CMs. Taken together, we demonstrate a potent ErbB2-mediated Yap mechanosensory signaling involving EMT-like characteristics, resulting in heart regeneration.
Project description:RNA-sequencing (RNA-Seq) protocols and bioinformatic pipelines are designed to streamline downstream analyses on sequences believed to be the most important. Here, we have challenged this dogma by preserving ribosomal RNA (rRNA) in our samples and by lowering the minimal RNA size window of our small RNA-Seq analyses to 8 nt
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes