Biology subjects

Thibault, P.

Publications and source records attributed to Thibault, P..

33 records · Page 2Linked to original sources

bioRxiv2022

Autophagy degrades immunogenic endogenous retroelements induced by 5-azacytidine in acute myeloid leukemia

The hypomethylating agent 5-azacytidine (AZA) is the first-line therapy for acute myeloid leukemia (AML) patients unfit for intensive chemotherapy. Evidence suggests that the anti-tumor effect of AZA results partly from T-cell cytotoxic responses against MHC-I-associated peptides (MAPs) whose expression is induced by hypomethylation. Through a proteogenomic approach, we analyzed the impact of AZA on the transcriptome and MAP repertoire of four AML cell lines and validated salient findings in the transcriptome of 437 primary AML samples. We demonstrate that AZA caused pleiotropic changes in AML cells via perturbation of transcription, translation, and protein degradation. Overall, 1,364 MAPs were upregulated in AZA-treated cells, including several cancer-testis antigens. Increased MAP abundance was due to the upregulation of corresponding transcripts in a minority of cases and post-translational events in most cases. Furthermore, AZA-induced hypomethylation increased the abundance of numerous transcripts, of which 38% were endogenous retroelements (EREs). Upregulated ERE transcripts triggered innate immune responses but were degraded by autophagy and not processed into MAPs. Autophagy resulted from the formation of protein aggregates caused by AZA-dependent inhibition of DNMT2, a tRNA-methyl transferase enzyme. We found that autophagy inhibition had a synergistic effect with AZA on AML cell proliferation and survival, increased ERE levels and triggered pro-inflammatory responses. Finally, autophagy gene signatures were associated with a lower abundance of CD8+ T-cell markers in AML patients expressing high levels of EREs. Altogether, this work demonstrates that the impact of AZA is regulated at several levels and suggests that inhibiting autophagy could improve the immune recognition of AML blasts in patients.

immunology↗

bioRxiv2022

BamQuery: a proteogenomic tool for the genome-wide exploration of the immunopeptidome

MHC-I-associated peptides (MAPs) derive from selective yet highly diverse genomic regions, including allegedly non-protein-coding sequences, such as endogenous retroelements (EREs). Quantifying canonical (exonic) and non-canonical MAPs-encoding RNA expression in malignant and benign cells is critical for identifying tumor antigens (TAs) but represents a challenge for immunologists. We present BamQuery, a computational tool attributing an exhaustive RNA expression to MAPs of any origin (exon, intron, UTR, intergenic) from bulk and single-cell RNA-sequencing data. We show that non-canonical MAPs (including TAs) can derive from multiple different genomic regions (up to 35,343 for EREs), abundantly expressed in normal tissues. We also show that supposedly tumor-specific mutated MAPs, viral MAPs, and MAPs derived from proteasomal splicing can arise from different unmutated non-canonical genomic regions. The genome-wide approach of BamQuery allows comprehensive mapping of all MAPs in healthy and cancer tissues. BamQuery can also help predict MAP immunogenicity and identify safe and actionable TAs.

immunology↗

bioRxiv2022

Immunological landscape of human lymph nodes during ex vivo measles virus infection

In humans, lymph nodes are the primary site of measles virus (MeV) replication. To understand the immunological events that occur at this site, we infected human lymphoid tissue explants using a pathogenic strain of MeV that expresses GFP. We found that MeV infected between 5-15% of cells across donors. Using single cell RNA-Seq (scRNA-Seq) and flow cytometry, we found that while most of the 29 cell populations identified in the lymphoid culture were susceptible to MeV, there was a broad preferential infection of B cells and reduced infection of T cells. Further subsetting of T cells revealed that this reduction may be driven by the decreased infection of naive T cells. Transcriptional changes in infected B cells were dominated by an interferon stimulated gene (ISG) signature. To determine which of these ISGs were most substantial, we evaluated the proteome of MeV-infected Raji cells by mass spectrometry. We found that IFIT1, IFIT2, IFIT3, ISG15, CXCL10, MX2, and XAF1 proteins were the most highly induced, and positively correlated with their expression in the transcriptome. These data provide insight into the immunological events that occur in lymph nodes during infection and may lead to the development of therapeutic interventions.

immunology↗

bioRxiv2020

Immunopeptidomics for Dummies: Detailed Experimental Protocols and Rapid, User-Friendly Visualization of MHC I and II Ligand Datasets with MhcVizPipe

Immunopeptidomics refers to the science of investigating the composition and dynamics of peptides presented by major histocompatibility complex (MHC) class I and class II molecules using mass spectrometry (MS). Here, we aim to provide a technical report to any non-expert in the field wishing to establish and/or optimize an immunopeptidomic workflow with relatively limited computational knowledge and resources. To this end, we thoroughly describe step-by-step instructions to isolate MHC class I and II-associated peptides from various biological sources, including mouse and human biospecimens. Most notably, we created MhcVizPipe (MVP) (https://github.com/CaronLab/MhcVizPipe), a new and easy-to-use open-source software tool to rapidly assess the quality and the specific enrichment of immunopeptidomic datasets upon the establishment of new workflows. In fact, MVP enables intuitive visualization of multiple immunopeptidomic datasets upon testing sample preparation protocols and new antibodies for the isolation of MHC class I and II peptides. In addition, MVP enables the identification of unexpected binding motifs and facilitates the analysis of non-canonical MHC peptides. We anticipate that the experimental and bioinformatic resources provided herein will represent a great starting point for any non-expert and will therefore foster the accessibility and expansion of the field to ultimately boost its maturity and impact.

bioinformatics↗

bioRxiv2020

SUMOylation- and GAR1-dependent regulation of dyskerin nuclear and subnuclear localization

Dyskerin, a telomerase-associated protein and H/ACA ribonucleoprotein complex component plays an essential role in human telomerase assembly and activity. The nuclear and subnuclear compartmentalization of dyskerin and the H/ACA complex is an important though incompletely understood aspect of H/ACA ribonucleoprotein function. The posttranslational modification, SUMOylation, targets a wide variety of proteins, including numerous RNA-binding proteins, and most identified targets reported to date localize to the nucleus. Four SUMOylation sites were previously identified in the C-terminal Nuclear/Nucleolar Localization Signal (N/NoLS) of dyskerin, each located within one of two lysine-rich clusters. We found that a cytoplasmic localized C-terminal truncation variant of dyskerin lacking most of the C-terminal N/NoLS and both lysine-rich clusters represents an under-SUMOylated variant of dyskerin compared to wildtype dyskerin. We demonstrate that mimicking constitutive SUMOylation of dyskerin using a SUMO3-fusion construct can drive nuclear accumulation of this variant, and that the SUMO site K467 in this N/NoLS is particularly important for the subnuclear localization of dyskerin to the nucleolus in a mature H/ACA complex assembly- and SUMO-dependent manner. We also characterize a novel SUMO-interacting motif in the mature H/ACA complex component GAR1 that mediates the interaction between dyskerin and GAR1. Mislocalization of dyskerin, either in the cytoplasm or excluded from the nucleolus, disrupts dyskerin function and leads to reduced interaction of dyskerin with the telomerase RNA. These data indicate a role for dyskerin C-terminal N/NoLS SUMOylation in regulating the nuclear and subnuclear localization of dyskerin, which is essential for dyskerin function as both a telomerase-associated protein and as an H/ACA ribonucleoprotein involved in rRNA and snRNA biogenesis.

cell biology↗

bioRxiv2020

SUMO Modifies GβL and Mediates mTOR Signaling

The mechanistic target of rapamycin (mTOR) signaling is influenced by multiple regulatory proteins and post-translational modifications, however, underlying mechanisms remains unclear. Here, we report a novel role of small ubiquitin-like modifier (SUMO) in mTOR complex assembly and activity. By investigating the SUMOylation status of core mTOR components, we observed that the regulatory subunit, G{beta}L, is modified by SUMO1, 2, and 3 isoforms. Using mutagenesis and mass spectrometry, we identified that G{beta}L is SUMOylated at lysine sites K86, K215, K245, K261 and K305. We found that SUMO depletion reduces mTOR-Raptor and mTOR-Rictor complex formation and diminishes nutrient-induced mTOR signaling. Furthermore, we found that reconstitution with WT G{beta}L but not SUMOylation defective KR mutant G{beta}L promote mTOR signaling in G{beta}L-depleted cells. Taken together, we report for the very first time that SUMO modifies G{beta}L, influences the assembly of mTOR protein complexes, and regulates mTOR activity.

biochemistry↗

bioRxiv2020

Early defects in lysosomal storage diseases disrupt excitatory synaptic transmission

At least two thirds of patients affected with lysosomal storage disorders (LSD) exhibit neurological symptoms. For mucopolysaccharidosis type IIIC (MPS IIIC, Sanfilippo disease type C) caused by mutations in the HGSNAT gene and lysosomal storage of heparan sulfate the major burden is progressive and severe neuropsychiatric problems, mental retardation, and dementia though to be mainly mediated by neurodegeneration. HGSNAT knockout mice match human clinical phenotype and develop hyperactivity followed by memory impairment and death. In order to understand whether early clinical symptoms in MPS IIIC mice occurring before the onset of massive neurodegeneration are caused by neuronal dysfunction we studied synaptic transmission and morphology in cultured hippocampal and CA1 pyramidal neurons of MPSIIIC mice. Synaptic spines were also studied in other mouse LSD models and postsynaptic densities in post-mortem cortices of human neurological MPS patients. Cultured hippocampal and CA1 pyramidal neurons of MPS IIIC mice showed a drastic decrease or abnormal distribution of multiple pre- and postsynaptic proteins that could be rescued in vitro and in vivo by virus-mediated gene correction. Dendritic spine densities were immature in cultured hippocampal MPS IIIC mouse neurons and reduced in pyramidal neurons of mouse models of MPS IIIC and other (Tay-Sachs, sialidosis) LSD starting from postnatal day 10. MPS IIIC neurons presented alterations in frequency and amplitude of miniature excitatory and inhibitory postsynaptic currents, sparse synaptic vesicles, reduced postsynaptic densities, disorganised microtubule network and partially impaired axonal transport of synaptic proteins. Postsynaptic densities were also reduced in post-mortem cotrees of human MPS I, II, IIIA, C and D patients suggesting that the pathology is common for these neurological LSD. Together, our results demonstrate that lysosomal storage causes alterations in synaptic structure and abnormalities in neurotransmission originating from disrupted vesicular transport and preceding the first cognitive symptoms and suggest drugs known to affect synaptic transmission can be potentially applied to treat behavioral and cognitive defects in neurological LSD patients.

neuroscience↗

bioRxiv2020

Rhes, a Striatal Enriched Protein, Regulates Post-Translational Small-Ubiquitin-like-Modifier (SUMO) Modification of Nuclear Proteins and Alters Gene Expression

Rhes (Ras homolog enriched in the striatum) is a multifunctional protein that orchestrates striatal toxicity, motor behaviors and abnormal movements associated with dopaminergic signaling, Huntington disease and Parkinson disease signaling in the striatum. Rhes engineers membranous tunneling nanotube-like structures and promotes intercellular protein and cargoes transport. Recent study revealed Rhes also regulates mitophagy via the Nix receptor. Despite these studies, the mechanisms through which Rhes mediates these diverse functions remains unclear. Rhes belongs to a small GTPase family member and consists of a unique C-terminal Small Ubiquitin-like Modifier (SUMO) E3-like domain that promotes the post-translational modification (PTM) of proteins with SUMO (SUMOylation) by promoting "cross-SUMOylation" of SUMO enzymes SUMO E1 (Aos1/Uba2) and SUMO E2 ligase (Ubc-9). However, the identity of the SUMO substrates of Rhes remains largely unknown. By combining high throughput interactome and SUMO proteomics we report that Rhes regulates the SUMOylation of nuclear proteins that are involved in the regulation of gene transcription. While Rhes has increased the SUMOylation of histone deacetylase 1 (HDAC1) and histone 2B, it had decreased the SUMOylation of heterogeneous nuclear ribonucleoprotein M (HNRNPM), protein polybromo-1 (PBRM1) and E3 SUMO-protein ligase (PIASy). We also found that Rhes itself is SUMOylated at 5 different lysine residues (K32, K110, K114, K120, K124 and K245). Furthermore, we found that Rhes regulates the expression of genes involved in cellular morphogenesis and differentiation in the striatum, in a SUMO-dependent manner. Our findings thus provide a previously undescribed role for Rhes in regulating SUMOylation of nuclear targets and in orchestrating striatal gene expression via the SUMOylation.

biochemistry↗

bioRxiv2020

Cyclin B3 activates the Anaphase-Promoting Complex/Cyclosome in meiosis and mitosis

In mitosis and meiosis, chromosome segregation is triggered by the Anaphase-Promoting Complex/Cyclosome (APC/C), a multi-subunit ubiquitin ligase that targets proteins for degradation, leading to the separation of chromatids. APC/C activation requires phosphorylation of its APC3 and APC1 subunits, which allows the APC/C to bind its Cdc20 co-activator. The identity of the kinase(s) responsible for APC/C activation in vivo is unclear. Cyclin B3 is required for meiotic anaphase in flies, worms and vertebrates, but whether it activates the APC/C is unclear. We found that Drosophila Cyclin B3 (CycB3) collaborates with PP2A-B55/Tws in embryonic development, indicating that CycB3 also promotes anaphase in mitosis. Moreover, CycB3 promotes APC/C activity and anaphase in cells in culture. We show that CycB3 physically associates with the APC/C, is required for phosphorylation of APC3, and promotes APC/C association with its co-activators. We propose that CycB3-Cdk1 directly phosphorylates the APC/C to activate it in both meiosis and mitosis.

cell biology↗

bioRxiv2020

Codon arrangement modulates MHC-I peptides presentation

MHC-I associated peptides (MAPs) play a central role in the elimination of virus-infected and neoplastic cells by CD8 T cells. However, accurately predicting the MAP repertoire remains difficult, because only a fraction of the transcriptome generates MAPs. In this study, we investigated whether codon arrangement (usage and placement) regulates MAP biogenesis. We developed an artificial neural network called Codon Arrangement MAP Predictor (CAMAP), predicting MAP presentation solely from mRNA sequences flanking the MAP-coding codons (MCCs), while excluding the MCC per se. CAMAP predictions were significantly more accurate when using original codon sequences than shuffled codon sequences which reflect amino acid usage. Furthermore, predictions were independent of mRNA expression and MAP binding affinity to MHC-I molecules and applied to several cell types and species. Combining MAP ligand scores, transcript expression level and CAMAP scores was particularly useful to increaser MAP prediction accuracy. Using an in vitro assay, we showed that varying the synonymous codons in the regions flanking the MCCs (without changing the amino acid sequence) resulted in significant modulation of MAP presentation at the cell surface. Taken together, our results demonstrate the role of codon arrangement in the regulation of MAP presentation and support integration of both translational and post-translational events in predictive algorithms to ameliorate modeling of the immunopeptidome. Author summaryMHC-I associated peptides (MAPs) are small fragments of intracellular proteins presented at the surface of cells and used by the immune system to detect and eliminate cancerous or virus-infected cells. While it is theoretically possible to predict which portions of the intracellular proteins will be naturally processed by the cells to ultimately reach the surface, current methodologies have prohibitively high false discovery rates. Here we introduce an artificial neural network called Codon Arrangement MAP Predictor (CAMAP) which integrates information from mRNA-to-protein translation to other factors regulating MAP biogenesis (e.g. MAP ligand score and transcript expression levels) to improve MAP prediction accuracy. While most MAP predictive approaches focus on MAP sequences per se, CAMAPs novelty is to analyze the MAP-flanking mRNA sequences, thereby providing completely independent information for MAP prediction. We show on several datasets that the integration of CAMAP scores with other known factors involved in MAP presentation (i.e. MAP ligand score and mRNA expression) significantly improves MAP prediction accuracy, and further validate CAMAP learned features using an in-vitro assay. These findings may have major implications for the design of vaccines against cancers and viruses, and in times of pandemics could accelerate the identification of relevant MAPs of viral origins.

bioinformatics↗

bioRxiv2020

Nsr1, a nitrogen source-regulated microprotein, confers an alternative mechanism of G1/S transcriptional activation in budding yeast

Commitment to cell division at the end of G1 phase, termed Start in the budding yeast Saccharomyces cerevisiae, is strongly influenced by nutrient availability. To identify new dominant activators of Start that might operate under different nutrient conditions, we screened a genome-wide ORF overexpression library for genes that bypass a Start arrest caused by absence of the G1 cyclin Cln3 and the transcriptional activator Bck2. We recovered a hypothetical gene YLR053c, renamed NRS1 for Nitrogen-Responsive Start regulator 1, which encodes a poorly characterized 108 amino acid microprotein. Endogenous Nrs1 was nuclear-localized, restricted to poor nitrogen conditions, induced upon mTORCl inhibition, and cell cycle-regulated with a peak at Start. NRS1 interacted genetically with SWI4 and SWI6, which encode subunits of the main G1/S transcription factor complex SBF. Correspondingly, Nrs1 physically interacted with Swi4 and Swi6 and was localized to G1/S promoter DNA. Nrs1 exhibited inherent transactivation activity and fusion of Nrs1 to the SBF inhibitor Whi5 was sufficient to suppress other Start defects. Nrs1 appears to be a recently evolved microprotein that rewires the G1/S transcriptional machinery under poor nitrogeny conditions. Author SummarUnicellular microorganisms must adapt to ever-changing nutrient conditions and hence must adjust cell growth and proliferation to maximize fitness. In the budding yeast Saccharomyces cerevisiae, commitment to cell division, termed Start, is heavily influenced by nutrient availability. Our understanding of how Start is activated is based mainly on experiments carried out under rich nutrient conditions. To identify potential new Start regulators specific to poor nutrient environments, we screened for genes able to bypass a genetic Start arrest caused by loss of the G1 cyclin Cln3 and the transcriptional activator Bck2. This screen uncovered YLR053c, which we renamed NRS1 for Nitrogen-Responsive Start regulator. Sequence analysis across yeast species indicated that Nrs1 is a recently-evolved microprotein. We showed that NRS1 is nutrient- and cell cycle-regulated, and directly binds the main G1/S transcription factor complex SBF. We demonstrated that Nrs1 has an intrinsic trans-activation activity and provided genetic evidence to suggest that Nrs1 can bypass the requirement for normal Cln3-dependent activation of G1/S transcription. These results uncover a new mechanism of Start activation and illustrate how microproteins can rapidly emerge to rewire fundamental cellular processes.

cell biology↗

bioRxiv2020

An inability to maintain the ribonucleoprotein genomic structure is responsible for host detection of negative-sense RNA viruses

Cellular biology has a uniformity not shared amongst viruses. This is perhaps best exemplified by negative-sense RNA viruses that encode their genetic material as a ribonucleoprotein complex composed of genome, RNA-dependent RNA polymerase, and the nucleoprotein. Here we demonstrate that limiting nucleoprotein availability not only universally culminates in a replicative catastrophe for negative-sense RNA viruses, but it results in the production of aberrant genomic material and induction of the interferon-based host defenses. This dynamic illustrates the tremendous stress imposed on negative-sense RNA viruses during replication as genomic products accumulate in an environment that requires an increasing demand on nucleoprotein availability. We show that limiting NP by RNA interference or drug targeting blocks replication and primes neighboring cells through the production of interferon. Together, these results demonstrate that the nucleoprotein represents the Achilles heel of the entire phylum of negative-sense RNA viruses. Here we establish this principle for a diverse collection of human pathogens and propose that the nucleoprotein should be a primary target for the development of future antiviral drugs. HIGHLIGHTSO_LILimited levels of NP result in production of defective viral genomes C_LIO_LIDefective viral genomes and viral antagonists are key determinants of the host antiviral response C_LIO_LIThe host response and defective viral genome generation further exasperate NP availability C_LIO_LINP is an optimal drug target for the whole phylum of negative-sense RNA viruses C_LI

microbiology↗

bioRxiv2019

Quantitative proteomics identifies novel PIAS1 protein substrates involved in cell migration and motility

The Protein Inhibitor of Activated STAT 1 (PIAS1) is an E3 SUMO ligase that plays important roles in various cellular pathways, including STAT signaling, p53 pathway, and the steroid hormone signaling pathway. PIAS1 can SUMOylate PML (at Lys-65 and Lys-160) and PML-RAR promoting their ubiquitin-mediated degradation. Increasing evidence shows that PIAS1 is overexpressed in various human malignancies, including prostate and lung cancers. To understand the mechanism of action of PIAS1, we developed a quantitative SUMO proteomic approach to identify potential substrates of PIAS1 in a system-wide manner. Our analyses enabled the profiling of 983 SUMO sites on 544 proteins, of which 204 SUMO sites on 123 proteins were identified as putative PIAS1 substrates. These substrates are involved in different cellular processes, such as transcriptional regulation, DNA binding and cytoskeleton dynamics. Further functional studies on Vimentin (VIM), a type III intermediate filament protein involved in cytoskeleton organization and cell motility, revealed that PIAS1 exerts its effects on cell migration and cell invasion through the SUMOylation of VIM at Lys-439 and Lys-445 residues. VIM SUMOylation was necessary for its dynamic disassembly, and cells expressing a non-SUMOylatable VIM mutant showed reduced levels of proliferation and migration. Our approach not only provides a novel strategy for the identification of E3 SUMO ligase substrates, but also yields valuable biological insights into the unsuspected role of PIAS1 and VIM SUMOylation on cell motility.

cancer biology↗

bioRxiv2019

Genetic Landscape of Electron Transport Chain Complex I Dependency in Acute Myeloid Leukemia

Inhibition of oxidative phosphorylation (OXPHOS) is a promising therapeutic strategy in Acute Myeloid Leukemia (AML), but patients respond heterogeneously. Through chemically interrogation of 200 sequenced specimens, we identified Mubritinib as a strong in vitro and in vivo anti-leukemic compound, acting through ubiquinone-dependent inhibition of Electron Transport Chain complex I (ETC1). ETC1 targeting showed selective toxicity against a subgroup of chemotherapy-resistant leukemias exhibiting OXPHOS hyperactivity, high expression of mitochondrial activity-related genes, and mutations affecting NPM1, FLT3 and DNMT3A. Altogether, our work thus identifies a novel ETC1 inhibitor with high clinical potential and reveals the landscape of OXPHOS dependency in AML.

cancer biology↗

bioRxiv2018

Transiently depleting RNPS1 leads to perdurable changes in alternative splicing

While robust regulatory mechanisms are expected to control the production of splice variants that confer distinct functions, a low level of stochasticity may be tolerated. To investigate stringency of regulation, we followed changes in the splicing of 192 alternative cassette exons after growth of cancer-derived HCT116 cells and embryonic colonocytes. In both cell lines approximately 15% of alternative splicing events changed by more than 10 percentage points over a 42-day period. We then carried out a cycle of transient depletions targeting RNPS1, a splicing regulator implicated in genomic stability. For alternative splicing units not regulated by RNPS1, the level of splicing changes was similar to the stochastic value obtained after normal growth. However, the frequency of perdurable changes was at least twice that value for splicing events regulated by RNPS1. A swap allele assay performed on four RNPS1-responsive units that underwent splicing changes indicated the presence of mutations mediating this effect. Specifically, a T to C mutation in a RNPS1-responsive exon of ADARB1 confered exon skipping. Our results suggest that fluctuations in the level of a splicing regulator preferentially impact the integrity of genes encoding transcripts that are regulated by this splicing factor to produce perdurable changes in alternative splicing. We discuss the potential implication of this process in human evolution.

molecular biology↗