Project description:The functionally redundant ubiquitin E3 ligases SIAH1 and SIAH2 have been implicated in the regulation of several processes, but their role in inflammatory signaling and gene expression remains unclear. Here we have downregulated the expression of both SIAH proteins with specific siRNAs and investigated the functional consequences for IL-1α-induced gene expression and the signaling pathways activating NF-κB and AP1. The knockdown of SIAH1/2 had no significant impact on IL-1α-induced activation of NF-κB and MAPK signaling pathways, but modulated the expression of approximately one third of IL-1α-regulated genes. Most of the proteins encoded by SIAH1/2-regulated genes form a regulatory network of proinflammatory factors. Thus SIAH1/2 proteins function as variable rheostats that control the amplitude of inflammatory gene expression.
Project description:The majority of current therapeutics targeting plasma membrane receptors function by antagonizing ligand binding or enzymatic activities. Typical mammalian proteins, however, consist of multiple domains executing discrete but coordinated activities, and saturating inhibition of one functional domain often incompletely suppresses the totality of the protein’s function. Recent work on targeted protein degradation technologies including Proteolysis Targeting Chimeras (PROTACs) has highlighted clinically important distinctions between target inhibition and target degradation. However, the generation of heterobifunctional compounds requiring linkage of two small molecules, each with high affinity for their targets, is highly complex, particularly with respect to achieving oral bioavailability. Here we describe the development of Proteolysis Targeting Antibodies (PROTABs) that tether cell-surface E3 ubiquitin ligases to transmembrane proteins, resulting in target ubiquitination and subsequent degradation. PROTAB-mediated degradation drives deeper pathway inhibition than inhibitory antibodies and is functional in vivo. The scope of this technology is also demonstrated through the identification of additional cell surface E3 ubiquitin ligases that can function as “on demand” degraders of various cell surface proteins. The generality of this approach enables tissue-selective degradation, as suggested by the Wnt-responsive ligases RNF43 and ZNRF3. Furthermore, through engineering of various optimized antibody formats, we offer insights on the ground rules governing optimal target degradation. Taken together, this work describes a strategy for the rapid development of potent, bioavailable and tissue selective degradation of cell surface proteins.
Project description:Paeonia lactiflora restored skeletal muscle function and mass in cancer-bearing mice, through the downregulations of muscular NF-kB signalling and muscle-specific E3 ubiquitin ligases. This study provides experimental evidence that Paeonia lactiflora can be a plausible candidate for a therapeutic agent for cancer cachexia.
Project description:Testis-restricted melanoma antigen (MAGE) proteins are frequently hijacked in cancer and play a critical role in tumorigenesis. MAGEs assemble with E3 ubiquitin ligases and function as substrate adaptors that direct the ubiquitination of novel targets, including key tumor suppressors. However, how MAGEs recognize their targets is unknown and has impeded development of MAGE-directed therapeutics. Here, we report the structural basis for substrate recognition by MAGE ubiquitin ligases. Biochemical analysis of the degron motif recognized by MAGE-A11 and the crystal structure of MAGE-A11 bound to the PCF11 substrate uncovered a conserved substrate binding cleft (SBC) in MAGEs. Mutation of the SBC disrupted substrate recognition by MAGEs and blocked MAGE-A11 oncogenic activity. A chemical screen for inhibitors of MAGE-A11:substrate interaction identified 4-aminoquniolines as potent inhibitors of MAGE-A11 that show selective cytotoxicity. These findings provide important insights into the large family of MAGE ubiquitin ligases and identify approaches for development of cancer-specific therapeutics.
Project description:Transcriptome analysis by RNA-seq of lungs from control and Rfwd2 epithelial-specific conditional knockout mice at embryonic 13.5 day age. RFWD2, is an E3 ubiquitin ligase that modifies specific target proteins, priming their degradation via the ubiquitin proteasome system. Rfwd2 deficiency led to a striking halt in branching morphogenesis shortly after secondary branch formation. In the mutant lung, two ETS transcript factors essential for normal lung branching, ETV4 and ETV5, were upregulated at the protein, but not transcript level. Introduction of Etv loss-of-function alleles into the Rfwd2 mutant background attenuated the branching phenotype, suggesting that RFWD2 functions at least in part through degrading ETV proteins. As a number of E3 ligases are known to target factors important for lung development, our findings provides a preview of a protein-level regulatory network essential for lung branching morphogenesis.
Project description:The Hace1 E3 ligase is a tumor suppressor in stressed cells. Through unknown mechanisms, Hace1 indirectly targets the cyclin D1 proto-oncogene for proteasomal degradation during nutrient depletion. We now show that Hace1 targets HIF1alpha for VHL-dependent degradation during hypoxia. To better understand these diverse actions we performed mass spectrometry to identify Hace1-interacting proteins. We show that Hace1 interacts with cullin-associated NEDD8-dissociated protein 1 (CAND1) under nutrient depletion and hypoxia. CAND1 binds cullins and prevents their entry into cullin ring E3 ligase (CRL) complexes, thus blocking CRL activity. Hace1 binding releases CUL1/2 from CAND1, facilitating assembly of CRL complexes to degrade cyclin D1 and HIF1alpha, respectively. These findings suggest a broad role for Hace1 in regulating tumor suppressive CRL E3 ligases. In this study, we used gene expression profiling to characterize how Hace1 overexpression affect the transcriptional response to hypoxic stress Using Affymetrix exon-level microarrays, we compared the expression profile of HEK293 cells overexpressing either Hace1 or MSCV vector alone, under hypoxia or normoxia
Project description:To identify potential ubiquitin ligases that regulate BIK1 homeostasis,A total amount of 3 µg RNA per sample was used as input material for the RNA sample preparations. Sequencing libraries were generated using NEBNext® Ultra™ RNA Library Prep Kit for Illumina® (NEB, USA) following manufacturer’s recommendations and index codes were added to attribute sequences to each sample. We using an optimized data analysis workflow,
Project description:The Acetylation-dependent (Ac/) N-degron pathway degrades proteins through recognition of their acetylated N-termini (Nt) by E3-ligases called Ac/N-recognins. To date, specific Ac/N-recognins have not been defined in plants. Here we used molecular, genetic, and multi-omics approaches to characterise potential roles for Arabidopsis (Arabidopsis thaliana) DEGRADATION OF ALPHA2 10 (DOA10)-like E3-ligases in the Nt-acetylation-(NTA-) dependent turnover of proteins at global and protein-specific scales. Arabidopsis has two ER-localised DOA10-like proteins. AtDOA10A, but not the Brassicaceae-specific AtDOA10B, can compensate for loss of yeast (Saccharmoyces cerevisiae) ScDOA10 function. Transcriptome and Nt-acetylome profiling of an Atdoa10a/b RNAi mutant revealed no obvious differences in the global NTA profile compared to wildtype, suggesting that AtDOA10s do not regulate the bulk turnover of NTA substrates. Using protein steady-state and cycloheximide-chase degradation assays in yeast and Arabidopsis, we showed that turnover of ER-localised squalene epoxidase 1 (AtSQE1), a critical sterol biosynthesis enzyme, is mediated by AtDOA10s. Degradation of AtSQE1 in planta did not depend on NTA, but Nt-acetyltransferases indirectly impacted its turnover in yeast, indicating kingdom-specific differences in NTA and cellular proteostasis. Our work suggests that, in contrast to yeast and mammals, targeting of Nt-acetylated proteins is not a major function of DOA10-like E3 ligases in Arabidopsis and provides further insight into plant ERAD and the conservation of regulatory mechanisms controlling sterol biosynthesis in eukaryotes.