Biology subjects

Alain, T.

Publications and source records attributed to Alain, T..

8 recordsLinked to original sources

bioRxiv2026

eIF4A inhibition disrupts resistance-associated translational and metabolic programs in BRAF-mutant melanoma

Acquired resistance to mitogen-activated protein kinase (MAPK) pathway inhibitors remains a major barrier to durable control of BRAF-mutant melanoma. Although resistance mechanisms are heterogeneous, they converge on adaptive programs that support survival, phenotypic plasticity, and metabolic fitness. We asked whether eukaryotic translation initiation factor 4A (eIF4A)-dependent mRNA translation represents a shared vulnerability of kinase inhibitor-resistant melanoma. Using matched BRAFV600E A375 and BRAF inhibitor-resistant A375R cells together with additional melanoma models, we integrated pharmacological and functional assays with polysome-associated RNA sequencing, quantitative proteomics, bioenergetic profiling, metabolomics, [U-13C5]glutamine tracing, and xenograft studies. Melanoma cells remained sensitive to multiple eIF4A inhibitors regardless of their responsiveness to BRAF inhibition. The eIF4A inhibitor CR-1-31-B rapidly reduced nascent protein synthesis when used alone in A375 cells and when added to the BRAF inhibitor PLX4032 in A375R cells; it also reduced BCL-2, CDK4, and cyclin D3 abundance, suppressed clonogenic growth, and induced apoptosis. Integrated analysis showed that acquired resistance involved broad RNA-abundance remodeling with superimposed changes in translational efficiency and buffering, affecting survival, extracellular-matrix and plasticity programs, and mitochondrial and metabolic functions. In resistant cells, CR-1-31-B induced early transcript-selective translational changes, accompanied at later time points by RNA-abundance and proteome remodeling. Publicly annotated 5' untranslated regions (5'UTRs) of CR-1-31-B-sensitive transcripts were enriched for purine-rich sequence architecture and local structural complexity. eIF4A inhibition preferentially attenuated the expression of proteins acquired during resistance and imposed a lower-output metabolic state in sensitive and resistant cells, reducing tricarboxylic-acid-cycle and pentose-phosphate-pathway metabolite pools and restricting intracellular glutamine-carbon transfer downstream of uptake. In A375 xenografts, CR-1-31-B delayed tumor growth, while its combination with PLX4720 produced deeper and more sustained tumor control and prolonged tumor endpoint-free survival compared with PLX4720 alone. These findings show that multiple resistance-associated programs spanning signaling, cell survival, and metabolism share a dependency on eIF4A-dependent translation and provide a preclinical rationale to test whether adding eIF4A inhibition can prolong responses to MAPK-targeted therapy in melanoma.

cancer biology↗

bioRxiv2023

Ribosome Quality Control Mechanism Mitigates the Cytotoxic Impacts of Ribosome Collisions Induced by 5-Fluorouracil

Translation of aberrant or damaged mRNAs results in ribosome stalling and collisions. The Ribosome Quality Control (RQC) mechanism detects collided ribosomes and removes aberrant mRNAs and nascent peptides, thus preventing their cytotoxic effects. Conversely, excessive or unresolved ribosome collisions can induce apoptosis. 5-Fluorouracil (5FU) forms the backbone of standard-of-care chemotherapeutic regimens for several types of cancer. Although best known for its incorporation into DNA and inhibition of thymidylate synthase, a major determinant of 5FUs anticancer activity is its incorporation into RNAs. Nevertheless, the mechanism(s) underlying RNA-dependent 5FU cytotoxicity and the cellular response to its impact on RNA metabolism remain unclear. Here, we report a key role for RQC in mitigating the cytotoxic effects of 5FU-induced dysregulation of mRNA translation. We show that acute 5FU treatment results in the rapid induction of the mTOR signalling pathway, an enhanced rate of mRNA translation initiation, and increased ribosome collisions that trigger RQC. We also found that RQC deficiency, caused by the depletion of ZNF598, results in increased 5FU-induced cell death, a phenotype that is reversed by inhibition of mTOR or repression of mRNA translation initiation. Importantly, 5FU treatment enhances the expression of key RQC factors, including ZNF598 and GIGYF2, via an mTOR-dependent post-translational regulation mechanism. This acute adaptation likely mitigates the cytotoxic consequences of increased ribosome collisions upon 5FU treatment. Overall, our data indicate a heretofore unknown mTOR-dependent mechanism that augments the RQC process, mitigating the cytotoxicity of 5FU and undermining its anticancer efficacy.

cell biology↗

bioRxiv2023

Repression of mRNA translation initiation by GIGYF1 via blocking the eIF3-eIF4G1 interaction

Viruses commonly interfere with the function of the eukaryotic translation initiation factor 4G1 (eIF4G1), a pivotal factor in the recruitment of the eIF3 complex and ribosome to the mRNA. This results in the inhibition of general host protein synthesis and redirecting ribosomes toward viral mRNAs. Certain viruses also selectively repress the translation of mRNAs involved in the host antiviral response. GIGYF2 and its interacting cap-binding protein 4EHP enable the transcript-specific repression of mRNA translation mediated by microRNAs and RNA-binding proteins (RBPs). RNA viruses, such as SARS-CoV-2, exploit the GIGYF2/4EHP complex to selectively repress the translation of transcripts such as Ifnb1 mRNA, which encodes the antiviral cytokine Interferon {beta} (IFN-{beta}). Herein, we reveal that GIGYF1, a paralogue of GIGYF2, robustly represses cellular mRNA translation through a distinct mechanism independent of 4EHP. Upon recruitment to a target mRNA by RBPs, the C-terminal region of GIGYF1 binds to subunits of eIF3 at the interaction interface of eIF3-eIF4G1. This disrupts binding of eIF3 to eIF4G1, resulting in mRNA-specific translational repression. This mechanism exerts profound influences on the host cells response to viral infection. Depletion of GIGYF1 induces a robust immune response by derepressing Ifnb1 mRNA translation. Overall, our study highlights a unique mechanism of translational regulation by GIGYF1 that involves sequestering eIF3 and abrogating its binding to eIF4G1. This mechanism can be utilized by RBPs that interact with GIGYF1 to specifically repress the translation of their target mRNAs, significantly affecting critical biological processes, including host-pathogen interactions.

cell biology↗

bioRxiv2022

SARS-CoV-2 impairs interferon production via NSP2-induced repression of mRNA translation

Viruses evade the innate immune response by suppressing the production or activity of cytokines such as type I interferons (IFNs). Here we report the discovery of a novel mechanism by which the SARS-CoV-2 virus co-opts an intrinsic cellular machinery to suppress the production of the key immunostimulatory cytokine IFN-{beta}. We reveal that the SARS-CoV-2 encoded Non-Structural Protein 2 (NSP2) directly interacts with the cellular GIGYF2 protein. This interaction enhances the binding of GIGYF2 to the mRNA cap-binding protein 4EHP, thereby repressing the translation of the Ifnb1 mRNA. Depletion of GIGYF2 or 4EHP significantly enhances IFN-{beta} production, leading to reduced viral infection. Our findings reveal a new target for rescuing the antiviral innate immune response to SARS-CoV-2 and other RNA viruses.

microbiology↗

bioRxiv2020

Identification of SARS-CoV2-mediated suppression of NRF2 signaling reveals a potent antiviral and anti-inflammatory activity of 4-octyl-itaconate and dimethyl fumarate

Antiviral strategies to inhibit Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) and the pathogenic consequences of COVID-19 are urgently required. Here we demonstrate that the NRF2 anti-oxidant gene expression pathway is suppressed in biopsies obtained from COVID-19 patients. Further, we uncover that NRF2 agonists 4-octyl-itaconate (4-OI) and the clinically approved dimethyl fumarate (DMF) induce a cellular anti-viral program, which potently inhibits replication of SARS-CoV2 across cell lines. The anti-viral program extended to inhibit the replication of several other pathogenic viruses including Herpes Simplex Virus-1 and-2, Vaccinia virus, and Zika virus through a type I interferon (IFN)-independent mechanism. In addition, induction of NRF2 by 4-OI and DMF limited host inflammatory responses to SARS-CoV2 infection associated with airway COVID-19 pathology. In conclusion, NRF2 agonists 4-OI and DMF induce a distinct IFN-independent antiviral program that is broadly effective in limiting virus replication and suppressing the pro-inflammatory responses of human pathogenic viruses, including SARS-CoV2. One Sentence SummaryNRF2 agonists 4-octyl-itaconate (4-OI) and dimethyl fumarate inhibited SARS-CoV2 replication and virus-induced inflammatory responses, as well as replication of other human pathogenic viruses.

microbiology↗

bioRxiv2019

Translational profiling of macrophages infected with Leishmania donovani identifies mTOR- and eIF4A-sensitive immune-related transcripts

The protozoan parasite Leishmania donovani (L. donovani) causes visceral leishmaniasis, a chronic infection which is fatal when untreated. While previous studies showed that L. donovani reprograms transcription to subvert host cell functions, it remains unclear whether the parasite also alters host mRNA translation to establish a successful infection. To assess this, we compared transcriptome-wide translation in primary mouse macrophages infected with L. donovani promastigotes or amastigotes using polysome-profiling. This identified ample selective changes in translation (3,127 transcripts) which were predicted to target central cellular functions by inducing synthesis of proteins related to chromatin remodeling and RNA metabolism while inhibiting those related to intracellular trafficking and antigen presentation. Parallel quantification of protein and mRNA levels for a set of transcripts whose translation was activated upon L. donovani infection (Papbpc1, Eif2ak2, and Tgfb) confirmed, as indicated by polysome-profiling, increased protein levels despite largely unaltered mRNA levels. Mechanistic in silico analyses suggested activated translation depending on the kinase mTOR (e.g. Pabpc1) and the RNA helicase eIF4A (e.g. Tgfb) during infection. Accordingly, treatment with mTOR inhibitors torin-1 or rapamycin reversed L. donovani-induced PABPC1 without affecting corresponding transcript levels. Similarly, the production of TGF-{beta} decreased in presence of the eIF4A inhibitor silvestrol despite unaltered Tgfb mRNA levels. Consistent with parasite modulation of host eIF4A-sensitive translation to promote infection, silvestrol suppressed L. donovani replication within macrophages. In contrast, parasite survival was favored under mTOR inhibition. In summary, infection-associated changes in translation of mTOR- and eIF4A-sensitive mRNAs contribute to modulate mRNA metabolism and immune responses in L. donovani-infected macrophages. Although the net outcome of such translation programs favours parasite propagation, individual translation programs appear to have opposing roles during L. donovani infection, thereby suggesting their selective targeting as key for therapeutic effects. Author SummaryFine-tuning the efficiency of mRNA translation into proteins allows cells to tailor their responses to stress without the need for synthesizing new mRNA molecules. It is well established that the protozoan parasite Leishmania donovani alters transcription of specific genes to subvert host cell functions. However, discrepancies between transcriptomic and proteomic data suggest that post-transcriptional regulatory mechanisms also contribute to modulate host gene expression programs during L. donovani infection. Herein, we report that one third of protein-coding mRNAs expressed in macrophages are differentially translated upon infection with L. donovani. Our computational analyses reveal that subsets of mRNAs encoding functionally related proteins share the same directionality of translational regulation, which is likely to impact metabolic and microbicidal activity of infected cells. We also show that upregulated translation of transcripts that encode central regulators of mRNA metabolism and inflammation is sensitive to the activation of mTOR or eIF4A during infection. Finally, we observe that inhibition of eIF4A activity reduces parasite survival within macrophages while selective blockade of mTOR has the opposite effect. Thus, our study points to a dual role for translational control of host gene expression during L. donovani infection and suggests that novel regulatory nodes could be targeted for therapeutic intervention.

immunology↗

bioRxiv2019

Induction of an alternative 5’ leader enhances translation of Inpp5e and resistance to oncolytic virus infection

Residual cell-intrinsic innate immunity in cancer cells hampers infection with oncolytic viruses. mRNA translation is an important component of innate immunity, yet the targeted cellular mRNAs remain ill-defined. We characterized the translatome of resistant murine \"4T1\" breast cancer cells infected with three of the most clinically advanced oncolytic viruses: Herpes Simplex virus 1, Reovirus and Vaccinia virus. Common among all three infections were translationally de-repressed mRNAs involved in ciliary homeostasis including Inpp5e, encoding an inositol 5-phosphatase that modifies lipid second messenger signalling. Translationally repressed in the uninfected condition, viral infection induced expression of an Inpp5e mRNA variant that lacks repressive upstream open reading frames (uORFs) within its 5 leader and is consequently efficiently translated. Furthermore, we show that INPP5E contributes to antiviral immunity by altering virus attachment. These findings uncover a role for translational control through alternative 5 leader expression and assign ciliary proteins such as INPP5E to the cellular antiviral response.

molecular biology↗

bioRxiv2018

LARP1 is a major phosphorylation substrate of mTORC1

The mammalian target of rapamycin complex 1 (mTORC1) controls critical cellular functions such as protein synthesis, lipid metabolism, protein turnover and ribosome biogenesis through the phosphorylation of multiple substrates. In this study, we examined the phosphorylation of a recently identified target of mTORC1: La-related protein 1 (LARP1), a member of the LARP superfamily. Previously, we and others have shown that LARP1 plays an important role in repressing TOP mRNA translation downstream of mTORC1. LARP1 binds the 7-methylguanosine triphosphate (m7Gppp) cap moiety and the adjacent 5terminal oligopyrimidine (5TOP) motif of TOP mRNAs, thus impeding the assembly of the eIF4F complex on these transcripts. mTORC1 plays a critical role in the control of TOP mRNA translation via LARP1 but the precise mechanism by which this occurs is incompletely understood. The data described herein help to elucidate this process. Specifically, it show that: (i) mTORC1 interacts with LARP1, but not other LARP superfamily members, via the C-terminal region that comprises the DM15 domain, (ii) mTORC1 pathway controls the phosphorylation of multiple (up to 26) serine and threonine residues on LARP1 in vivo, (iii) mTORC1 regulates the binding of LARP1 to TOP mRNAs and (iv) phosphorylation of S689 by mTORC1 is particularly important for the association of the DM15 domain of LARP1 with the 5UTR of RPS6 TOP mRNA. These data reveal LARP1 as a major substrate of mTORC1.

biochemistry↗