Biology subjects

Freniere, C.

Publications and source records attributed to Freniere, C..

5 recordsLinked to original sources

bioRxiv2026

A Hybrid Gag Lattice as a Structural Intermediate in HIV-1 Maturation

HIV-1 maturation converts the spherical immature Gag lattice into the conical mature capsid required for infectivity, yet the structural route linking these two lattice endpoints remains unclear. Using single-particle cryo-electron microscopy and cryo-electron tomography on reconstituted assemblies and virus-like particles (VLPs), we identify a distinct hybrid lattice in which the capsid protein (CA) N-terminal domain adopts a mature-like conformation, whereas the CA C-terminal domain-SP1 layer remains immature. This architecture is observed in native, enveloped VLPs produced in human cells, demonstrating formation under physiologically relevant conditions. The hybrid lattice engages three myo-inositol hexakisphosphate (IP6) molecules per CA-SP1 hexamer, underscoring IP6-dependent stabilization; accordingly, excess IP6 enriches the hybrid population. Tomographic mapping shows that hybrid regions coexist with the immature lattice within the same particle and are enriched near lattice discontinuities, consistent with edge-localized remodeling that can accommodate conformational rearrangements and partial disassembly and reassembly. Disrupting a hybrid-specific inter-hexamer contact preserves immature lattice assembly and particle release but abrogates infectivity, compromises core integrity, and prevents mature lattice formation, implicating the hybrid architecture as an on-pathway intermediate. Molecular dynamics simulations further support coordinated rearrangements that bias the system away from the immature configuration toward hybrid and then mature organizations. Together, these results support a maturation model in which localized displacive remodeling and partial disassembly/reassembly act in concert, with IP6 tuning the balance among lattice states. This study provides new insight into HIV-1 maturation and identifies the hybrid lattice as a potential therapeutic target.

biochemistry↗

bioRxiv2025

Dissecting the unique self-assembly landscape of the HIV-2 capsid protein

Human immunodeficiency virus type 2 (HIV-2) is a lentivirus closely related to HIV-1 but exhibits distinct molecular and clinical features that influence viral infectivity and efficacy of antiretroviral therapy. The HIV capsid is a critical structural component with multifaceted roles during infection and mediates some of the observed divergence between HIV-1 and HIV-2. Unlike HIV-1, study of the HIV-2 capsid is limited and standard protocols for the in vitro assembly of HIV-1 capsid protein (CA) lattice structures have not been successfully translated to the HIV-2 context. This work identifies effective approaches for the assembly of the HIV-2 CA lattice and leverages this to biochemically characterize HIV-2 CA assemblies and mutant phenotypes. Our findings elaborate on the sensitivity of HIV-2 CA to chemical conditions and reveal that it assembles into a more varied spectrum of particle morphologies compared to HIV-1. Utilizing these assemblies, we tested the hypothesis that HIV-1 and HIV-2 employ divergent mechanisms to stabilize CA oligomer forms and investigate the effects of non-conserved substitutions at the CA inter-protomer interfaces. This work advances our understanding of the key biochemical determinants of HIV-2 CA assembly that are distinct from HIV-1 and may contribute to their divergent virological properties.

biochemistry↗

bioRxiv2024

Structural insights into HIV-2 CA lattice formation and FG-pocket binding revealed by single particle cryo-EM.

One of the most striking features of HIV is the capsid; a fullerene cone comprised of the pleomorphic capsid protein (CA) which shields the viral genome from cellular defense mechanisms and recruits cellular cofactors to the virus. Despite significant advances in understanding the mechanisms of HIV-1 CA assembly and host factor interaction, HIV-2 CA remains poorly understood. By templating the assembly of HIV-2 CA on functionalized liposomes, we were able to determine high resolution structures of the HIV-2 CA lattice, including both CA hexamers and pentamers, alone and in complexes with peptides of host phenylalanine-glycine (FG)-motif proteins Nup153 and CPSF6. While the overall fold and mode of binding the FG-peptides are conserved with HIV-1, this study reveals distinctive structural features that define the HIV-2 CA lattice, potential differences in interactions with other host factors such as CypA, and divergence in the mechanism of formation of hexameric and pentameric CA assemblies. This study extends our understanding of HIV capsids and highlights an approach with significant potential to facilitate the study of lentiviral capsid biology.

biochemistry↗

bioRxiv2024

Structural insights into inhibitor mechanisms on immature HIV-1 Gag lattice revealed by high-resolution in situ single-particle cryo-EM

HIV-1 inhibitors, such as Bevirimat (BVM) and Lenacapavir (LEN), block the production and maturation of infectious virions. However, their mechanisms remain unclear due to the absence of high-resolution structures for BVM complexes and LENs structural data being limited to the mature capsid. Utilizing perforated virus-like particles (VLPs) produced from mammalian cells, we developed an approach to determine in situ cryo-electron microscopy (cryo-EM) structures of HIV-1 with inhibitors. This allowed for the first structural determination of the native immature HIV-1 particle with BVM and LEN bound inside the VLPs at high resolutions. Our findings offer a more accurate model of BVM engaging the Gag lattice and, importantly, demonstrate that LEN not only binds the mature capsid but also targets the immature lattice in a distinct manner. The binding of LEN induces a conformational change in the capsid protein (CA) region and alters the architecture of the Gag lattice, which may affect the maturation process. These insights expand our understanding of the inhibitory mechanisms of BVM and LEN on HIV-1 and provide valuable clues for the design of future inhibitors.

biochemistry↗

bioRxiv2021

Cytoskeletal regulation of a transcription factor by DNA mimicry

A long-established strategy for transcription regulation is the tethering of transcription factors to cellular membranes. In contrast, the principal effectors of Hedgehog signaling, the Gli transcription factors, are regulated by microtubules in the primary cilium and the cytoplasm. How Gli is tethered to microtubules remains unclear. We uncover DNA mimicry by the ciliary kinesin Kif7 as a mechanism for the recruitment of Gli to microtubules, revealing a new mode of tethering a DNA-binding protein to the cytoskeleton. Gli increases the Kif7-microtubule affinity and consequently modulates the localization of both proteins to microtubules and the cilium tip. Thus, the kinesin-microtubule system is not a passive Gli tether but a regulatable platform tuned by the kinesin-transcription factor interaction. We re-tooled the unique DNA-mimicry-based Gli-Kif7 interaction for inhibiting the nuclear and cilium localization of Gli. This strategy can be potentially exploited for downregulating erroneously activated Gli in human cancers.

cell biology↗