Project description:GFI is a DNA binding transcriptional repressor that regulates myeloid differentiation. Here, we show that GFI1 interacts with the chromodomain helicase CHD4 and other components of the nucleosome remodeling and deacetylase (NuRD) complex. Our data demonstrated that GFI1 and GFI1/CHD4 complexes occupy sites of open chromatin enriched for histone marks associated with active transcription or different sets of genes that are either enriched for IRF1 or SPI-1 consensus binding sites. In addition, our study provided evidence that GFI1 affects the chromatin remodeling activity of the NuRD complex. Overall, our results indicate that GFI1/CHD4 complexes control chromatin openness and histone modifications differentially to regulate target genes, which govern the immune response, nucleosome organization, or metabolic processes.
Project description:RAB GTPases represent the most abundant family of small GTPases and regulate multiple aspects of membrane trafficking events, from cargo sorting to vesicle budding, transport, docking, and fusion. To control these processes, RABs are tightly regulated by guanine exchange factors (GEFs) and GTPase-activating proteins (GAPs). Activated RABs recruit effector proteins to regulate trafficking events. Identifying RAB-associated proteins has proved difficult, as their association is often transient. Recent advances in proximity labeling approaches that allow for covalently labeling protein neighbors of proteins of interest now permit cataloging proteins in the vicinity of RAB GTPases. Here, we provide APEX2 proximity labeling on 23 human RABs and their neighboring proteomes.
Project description:Centrosomes ensure accurate chromosome segregation during cell division. Although the regulation of centrosome number is well-established, less is known about the suppression of non-centrosomal Microtubule-Organising Centres (ncMTOCs). The E3 ligase TRIM37, implicated in Mulibrey nanism and 17q23-amplified cancers, has emerged as a key regulator of both centrosomes and ncMTOCs. Yet, the mechanism by which TRIM37 achieves enzymatic activation to target these mesoscale structures had thus far remained unknown. Here, we elucidate the activation process of TRIM37, unveiling a process that initiates with TRAF domain-directed substrate recognition, followed by B-box domain-mediated oligomerisation, and culminates in RING domain dimerisation. Using optogenetics, we demonstrate that the E3 activity of TRIM37 is directly coupled to the assembly state of its substrates, being activated only when centrosomal proteins cluster into higher-order assemblies resembling MTOCs. This regulatory framework provides a mechanistic basis for understanding TRIM37-driven pathologies and echoes the restriction of the HIV capsid by TRIM5, thus unveiling a conserved activation blueprint among TRIM proteins to control turnover of complexes assembled at the mesoscale level.
Project description:Deciphering the intricate dynamic events governing type I interferon (IFN) signaling is critical to unravel key regulatory mechanisms in host antiviral defense. Here, we leveraged TurboID-based proximity labeling coupled with affinity purification-mass spectrometry to comprehensively map temporal changes to the proximal human proteomes of all seven canonical type I IFN signaling cascade members following IFN stimulation. This established a network of 108 proteins in close proximity to the core members IFNAR1, IFNAR2, JAK1, TYK2, STAT1, STAT2, and IRF9, and validated several known protein assemblies, while also revealing novel, transient associations between key signaling molecules.
Project description:Integrin adhesion complexes (IACs) bridge the extracellular matrix to the actin cytoskeleton and transduce signals in response to both chemical and mechanical cues. The composition, interactions, stoichiometry and topological organisation of proteins within IACs are not fully understood. To address this gap, we used multiplexed proximity biotinylation (BioID) to generate an in situ, proximity-dependent adhesome. Integration of the interactomes of 16 IAC-associated baits revealed a network of 147 proteins with 361 proximity interactions. Candidates with underappreciated roles in adhesion were identified, in addition to established IAC components. Bioinformatic analysis revealed five clusters of IAC baits that link to common groups of prey, and which therefore may represent functional modules. The five clusters, and their spatial associations, are consistent with current models of IAC interaction networks and stratification. This study provides a resource to examine proximal relationships within IACs on a global level.
Project description:This study evaluates liquid-chromatography operated at 50 ul/min using 1 mm diameter columns coupled online to tandem mass spectrometry (LC-MS/MS) for proteome analysis. Data from >1,000 human cell line, tissue, body fluid, affinity- and phospho-proteomes demonstrate excellent chromatographic (<0.3 % CV) and quantitative (<7.5% CV) reproducibility. Combined with sample multiplexing by tandem mass tags, the system allows profiling of 11 proteomes in 16 hours to a depth of 8,000 proteins.
Project description:During the purification of recombinantely expressed MRAS and MRAS mutants, there were additional proteins which appeared to co-precipitate and were detected by Coomassie staining. Since the apparent molecular weight was within the range for small GTPase proteins, we sought to determine the identity of these proteins.
Project description:Hepatocyte nuclear factor 4 (HNF4) is a transcription factor that acts as a master regulator of genes in several endodermal-derived tissues, including the intestine in which it plays a central role during development and tumorigenesis. To better delineate the mechanisms by which HNF4 can interfere during these processes, we combined stable isotope labelling with amino acids in cell culture (SILAC)-based quantitative proteomics with immunoprecipitation of green fluorescent protein (GFP) as well as with proximity-dependent purification by the biotin ligase BirA, both fused to HNF4. Surprisingly, these analyses identified a significant enrichment of proteins falling into the DNA repair gene ontology term, a so far unidentified biological feature of this transcription factor. Several of these proteins including PARP1, RAD50 and DNA-PKcs were confirmed to interact with HNF4in colorectal cancer cell lines. During DNA damage response, HNF4 localized to double strand DNA breaks in these cells. HNF4was able to interfere functionally during non-homologous end-joining (NHEJ). Overall, these observations identify an unsuspected role for this transcription factor during the DNA damage response.
Project description:Synucleinopathies are characterized by the accumulation and propagation of α-synuclein (α-syn) aggregates throughout the brain, leading to neuronal dysfunction and death. In this study, we used an unbiased FACS-based genome-wide CRISPR/Cas9 knockout screening to identify genes that regulate the entry and accumulation of α-syn preformed fibrils (PFFs) in cells. We identified key genes and pathways specifically implicated in α-syn PFFs intracellular accumulation, including heparan sulfate proteoglycans (HSPG) biosynthesis and Golgi trafficking. All confirmed hits affected heparan sulfate (HS), a post-translational modification known to act as a receptor for proteinaceous aggregates including α-syn and tau. Intriguingly, deletion of SLC39A9 and C3orf58 genes, encoding respectively a Golgi-localized exporter of Zn 2+, and the Golgi-localized putative kinase DIPK2A, specifically impaired the uptake of α-syn PFFs, by preventing the binding of PFFs to the cell surface. Mass spectrometry- based analysis of HS chains in SLC39A9-/- and C3orf58-/- cells indicated major defects in HS homeostasis. Additionally, Golgi accumulation of NDST1, a prime HSPG biosynthetic enzyme, was detected in C3orf58-/- cells. Interestingly, C3orf58-/- human iPSC-derived microglia and dopaminergic neurons exhibited a strong reduction in their ability to internalize α-syn PFFs. Altogether, our data identifies new modulators of HSPGs that regulate α-syn PFFs cell surface binding and uptake.
Project description:Ubash3b, also known as suppressor of T-cell receptor signaling or Sts-1, is an ill-studied atypical tyrosine phosphatase with ubiquitin binding ability. In our previous study, we hypothesized that Ubash3b plays an inhibitory role in BCR-ABL signaling through binding and dephosphorylating BCR-ABL and its interactors. The Hantschel lab recently solved the crystal structures of the p210 PH and DH domains, which are absent in the p190 variant, and demonstrated that loss-of-function mutations in the PH domain altered BCR-ABL localization, thereby reducing the interaction between Ubash3b and p2104. Taken together, this suggests differential subcellular localization of Ubash3b as a mechanism by which it interacts more strongly with p201 as compared to p190. To better understand the global impact Ubash3b has on p210, its direct kinase substrates and proteins in its phosphotyrosine signaling network, we have taken an integrative approach by combining global phosphotyrosine profiling, proximity-dependent biotinylation (BioID) and total protein analysis to investigate p210 signaling upon Ubash3b knockdown (KD). The BioID system was used to characterize Ubash3b function in p210 signaling by examining its interactome. Importantly, in all of our BioID experiments, we employed a newly technique that we have recently developed, Biotinylation Site Identification Technology (BioSITe), which directly identifies biotinylated peptides thereby increasing the reliability of the identified interactors. Here, we additionally used short hairpin RNA (shRNA) interference and generated Ubash3b knock-down (KD) and non-targeting control shRNA lines in Ba/F3 BirA*-p210 cells. Ubash3b expression was reduced >90 % in the KD cells and had a substantial effect on global tyrosine phosphorylation and on the interactome of p210. Of the 1,421 unique tyrosine phosphorylation sites identified from 830 proteins, 379 sites (from 286 proteins) exhibited a substantial increase (≥2-fold) in tyrosine phosphorylation upon Ubash3b KD cells compared to control cells. To date, the interactome of Ubash3b has not been extensively investigated, however, some examination of Ubash3b in the context p210 signaling has been undertaken. We designed constructs of C-terminal BirA* tagged full length Ubash3b and a deletion mutant lacking the UBA and SH3 domains leaving only the phosphatase domain tethered to BirA*. A comparative analysis of the core interactors of p210 from previous studies and Ubash3b interactome from the current study revealed 36 proteins that interact with both p210 and Ubash3b.