Biology subjects

Barbeau, B.

Publications and source records attributed to Barbeau, B..

3 recordsLinked to original sources

bioRxiv2026

Antagonistic regulation of HBZ splicing by hnRNPA1 and hnRNPH1 drives HTLV-1 leukemogenesis.

Adult T-cell leukemia/lymphoma (ATL) is a highly aggressive leukemia driven by Human T-cell Leukemia Virus type 1 (HTLV-1) and remains largely refractory to current therapies. Although hbz is the only viral transcript consistently expressed in acute ATL, the extent to which its alternative splicing shapes disease biology remains unknown. Here, we demonstrate that the splicing of hbz plays a key role in driving cancer development in ATL. Quantitative analyses in HTLV-1-infected cell lines and primary samples revealed a striking enrichment of the spliced isoform HBZ_SP1 (over 200-fold) in CD4 T cells from ATL patients, whereas the unspliced transcript (usHBZ) predominates in CD8 T cells. Despite robust transcription, the usHBZ protein was undetectable, whereas HBZ_SP1 accumulated rapidly, identifying it as the main isoform in CD4 T cells from ATL patients. Furthermore, only HBZ_SP1 drove cellular transformation and conferred marked resistance to chemotherapeutic stress. Mechanistically, we identify a splicing regulatory axis centered on hnRNPA1 and hnRNPH1. Both proteins bind hbz pre-mRNA, but exert opposing effects: hnRNPA1 represses splicing, whereas hnRNPH1 promotes production of the oncogenic HBZ_SP1 isoform. Perturbation of this balance reprograms HBZ isoform expression and alters leukemic cell fitness. Collectively, our findings establish that HBZ inhibits hnRNPA1 transcription, therefore allowing HTLV-1 to hijack host RNA splicing and to generate an oncogenic isoform that drives transformation and chemoresistance. These results uncover a previously unrecognized post-transcriptional mechanism of viral leukemogenesis and position HBZ splicing and its regulators as therapeutic targets in ATL. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/739521v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1298adorg.highwire.dtl.DTLVardef@e5a7beorg.highwire.dtl.DTLVardef@167d576org.highwire.dtl.DTLVardef@1ef68f6_HPS_FORMAT_FIGEXP M_FIG C_FIG Mechanistic model of HBZ splicing regulation. This simplified graphical abstract summarizes the highlights of our study. Here, we hypothesize that in CD4+ T cells infected by HTLV-1, transcription and splicing reprogramming lead to a preferential expression of the HBZ_SP1 oncogenic isoform, specifically due to an overexpression of the splicing activator hnRNP H1and repression of hnRNP A1 by HBZ itself via C/EBP. HBZ_SP1 is consistently expressed and then drives cell transformation and chemoresistance. In contrast, in CD8+ T cells infected with HTLV-1, the HBZ-mediated downregulation of hnRNP A1 is overcome, leading to inhibition of HBZ splicing and increased expression of the less oncogenic isoform usHBZ.

molecular biology↗

bioRxiv2024

A novel SARS-CoV-2-derived infectious vector system

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19. The development of antiviral drugs for COVID-19 has been hampered by the requirement of a biosafety level 3 (BSL3) laboratory for experiments related to SARS-CoV-2, and by the lack of easy and precise methods for quantification of infection. Here, we developed a SARS-CoV-2 viral vector composed of all four SARS-CoV-2 structural proteins constitutively expressed in lentivirally transduced cells, combined with an RNA replicon deleted for SARS-CoV-2 structural protein genes S, M and E, and expressing a luciferase-GFP fusion protein. We show that, after concentrating viral stocks by ultracentrifugation, the SARS-CoV-2 viral vector is able to infect two human cell lines expressing receptors ACE2 and TMPRSS2. Both luciferase activity and GFP fluorescence were detected, and transduction was remdesivir-sensitive. We also show that this vector is inhibited by three type I interferons (IFN-I) subtypes. Although improvements are needed to increase infectious titers, this vector system may prove useful for antiviral drug screening and SARS-CoV-2-related investigations.

microbiology↗

bioRxiv2018

HIV-1 antisense protein of different clades induces autophagy and associates to the autophagy factor p62

Over recent years, strong support argues for the existence of an HIV-1 protein encoded by antisense transcripts and termed Antisense Protein (ASP). Furthermore, a recent in silico analysis has provided evidence for its recent appearance in the genome of HIV-1. We have previously detected ASP in various mammalian cell lines by Western blot (WB), flow cytometry and confocal microscopy analyses and reported that it induced autophagy, potentially through multimer formation. The aim of the current study was to examine autophagy induction by testing ASP from different clades, and to identify the implicated autophagy factors. We firstly confirmed that NL4.3-derived ASP was interacting with itself and that multimer formation was dependent on its amino region. Removal of this region was associated with reduced level of induced autophagy, as assessed by autophagosome formation but deletion of the most amino cysteine triplet did not totally abrogate multimer and autophagosome formation. Expression vectors of ASP from different clades were next tested and led to detection of monomers and varying levels of multimers with concomitant induced autophagy, as determined by increased LC3-II and decreased p62 (SQSTM1) levels. Through confocal microscopy, ASP was noted to co-localize with p62 and LC3-II in autophagosome-like cellular structures. CRISPR-based knock-out of ATG5, ATG7 and p62 genes led to increased stability in the levels of ASP. Furthermore, co-immunoprecipitation experiments demonstrated the interaction between p62 and ASP, which was dependent on the PB1 domain of p62. Interestingly, immunoprecipitation experiments further supported that ASP is ubiquitinated and that ubiquitination was also responsible for the modulation of its stability. We are thus suggesting that ASP induces autophagy through p62 interaction and that its abundance is controlled by autophagy- and Ubiquitin/Proteasome System (UPS)-mediated degradation in which ubiquitin is playing an important role. Understanding the mechanisms underlying the degradation of ASP is essential to better assess its function.\n\nAuthor SummaryIn the present study, we provide the first evidence that a new HIV-1 protein termed ASP when derived from different clades act similarly in inducing autophagy, an important cellular process implicated in the degradation of excess or defective material. We have gained further knowledge on the mechanism mediate the activation of autophagy and have identified an important interacting partner. Our studies have important ramification in the understanding of viral replication and the pathogenesis associated with HIV-1 in infected individuals. Indeed, autophagy is implicated in antigen presentation during immune response and could thus be rendered inefficient in infected cells, such as dendritic cells. Furthermore, a possible link with HIV-1-associated Neurological Disorder (HAND) might also be a possible association with the capacity of ASP to induce autophagy. Our studies are thus important and demonstrate the importance in conducting further studies on this protein, as it could represent a new interesting target for antiretroviral therapies and vaccine design.

microbiology↗