Biology subjects

Pourcelot, O.

Publications and source records attributed to Pourcelot, O..

4 recordsLinked to original sources

bioRxiv2025

Cell heterogeneity contributes to the variable response of HIV-1 to latency reversing agents

Transcriptional noise contributes to gene expression variability, but its origin and impact in HIV-1 latency remain incompletely characterized. Here, we combine a dual-copy MS2-tagging system with novel mathematical analysis to investigate the variability of HIV-1 transcription in live cells. In the basal state, the transcriptional activity of proviruses located in the same cell was uncorrelated, indicating that expression variability primarily comes from the intrinsic stochasticity of promoter dynamics. Upon stimulation with diverse latency-reversing agents, viral transcription became more correlated within cells than across them, revealing a shift from promoter-driven to cell state-driven variability. Analysis of the molecular drug targets confirmed variable effects across cells. Our findings indicates that cellular heterogeneity shapes the response to latency reversing agents and demonstrate how quantitative tools can dissect noise sources. This work offers mechanistic insights into HIV-1 latency and informs strategies to target the latent viral reservoir. TeaserLive transcription imaging reveals how cell heterogeneity contributes to the variability of HIV-1 activation.

molecular biology↗

bioRxiv2025

A Deep Learning approach for time-consistent cell cycle phase prediction from microscopy data

The cell cycle consists of four phases and impacts most cellular processes. In imaging assays, the cycle phase can be identified using dedicated cell-cycle markers. However, such markers occupy fluorescent channels that may be needed for other reporters. Here, we propose to address this limitation by inferring the phase from a widely used fluorescent reporter: SiR-DNA. Our method is based on a variational auto-encoder, enhanced with two auxiliary tasks: predicting the intensity of phase-specific markers and enforcing the latent space temporal consistency. Our model is freely available, along with a new dataset comprising over 600,000 annotated HeLa Kyoto nuclear images.

bioinformatics↗

bioRxiv2024

Cell cycle-dependent mRNA localization in P-bodies

Understanding the dynamics of RNA targeting to membraneless organelles is essential to disentangle their functions. Here, we investigate how P-bodies (PBs) evolve during cell cycle progression. PB purification across the cell cycle uncovers widespread changes in their RNA content, which are partly uncoupled from cell cycle-dependent changes in RNA expression. Single molecule FISH shows various mRNA localization patterns in PBs peaking in G1, S, or G2, with examples illustrating the timely capture of mRNAs in PBs when their encoded protein becomes dispensable. Yet, rather than directly reflecting absence of translation, cyclic mRNA localization in PBs can be controlled by RBPs, such as HuR in G2, and by RNA features. Indeed, while PB mRNAs are AU-rich at all cell cycle phases, they are specifically longer in G1, possibly related to post-mitotic PB reassembly. Altogether, our study supports a model where PBs are more than a default location for excess untranslated mRNAs.

cell biology↗

bioRxiv2022

The N-terminal domain of MX1 proteins is essential for their antiviral activity against different families of RNA viruses

Myxovirus resistance protein 1 (MX1) and MX2, are homologous, dynamin-like large GTPases, induced upon interferon (IFN) exposure. Human MX1 (HsMX1) is known to inhibit many viruses, including influenza A virus (IAV), by likely acting at various steps of their life cycles. Despite decades of studies, the mechanism(s) of action with which MX1 proteins manage to inhibit target viruses is not fully understood. MX1 proteins are mechano-enzymes and share a similar organization to dynamin, with an amino-terminal GTPase domain and a carboxy-terminal stalk domain, connected by a Bundle Signalling Element (BSE). These three elements are known to be essential for antiviral activity. HsMX1 has two unstructured regions, the L4 loop, also essential for antiviral activity, and a short amino (N)-terminal region, which greatly varies between MX1 proteins of different species. The role of this N-terminal domain in antiviral activity is not known. Herein, using mutagenesis, imaging and biochemical approaches, we demonstrate that the N-terminal domain of HsMX1 is essential for antiviral activity against IAV and Vesicular Stomatitis Virus (VSV), and for the ability to aggregate Orthobunyavirus nucleoproteins. Furthermore, we pinpoint a highly conserved leucine within this region, which is absolutely crucial for human, mouse and bat MX1 protein antiviral activity. Importantly, mutation of this leucine does not compromise GTPase activity or oligomerization capabilities, but does modify MX1 protein subcellular localisation. The discovery of this essential and highly conserved residue defines this region as key and may reveal insights as to the mechanism of action of MX1 proteins.

microbiology↗