Bernacchi, S. | Search bioRxiv

bioRxiv2024

HIV-1 budding requires cortical actin disassembly by the oxidoreductase MICAL1

Many enveloped viruses bud from the plasma membrane that is tightly associated with a dense and thick actin cortex. This actin network represents a significant challenge for membrane deformation and scission, and how it is remodeled during the late steps of the viral cycle is largely unknown. Using super-resolution microscopy, we show that HIV-1 buds in areas of the plasma membrane with low cortical F-actin levels. We find that the cellular oxidoreductase MICAL1 locally depolymerizes actin at budding sites to promote HIV-1 budding and release. In the absence of MICAL1, F-actin abnormally remains at viral budding sites, incompletely budded viruses accumulate at the plasma membrane and viral release is impaired. Remarkably, normal viral release can be restored in MICAL1-depleted cells by inhibiting Arp2/3-dependent branched actin networks. Mechanistically, we find that MICAL1 directly disassembles branched-actin networks and controls the timely recruitment of the ESCRT scission machinery during viral budding. In addition, the MICAL1 activator Rab35 is recruited at budding sites, functions in the same pathway as MICAL1 and is also required for viral release. This work reveals a role for oxidoreduction in triggering local actin depolymerization to control HIV-1 budding, a mechanism that may be widely used by other viruses. The debranching activity of MICAL1 could be involved beyond viral budding in various other cellular functions requiring local plasma membrane deformation.

cell biology↗

bioRxiv2020

The two zinc fingers in the nucleocapsid domain of the HIV-1 Gag precursor are equivalent for the interaction with the genomic RNA in the cytoplasm, but not for the recruitment of the complexes at the plasma membrane

The HIV-1 Gag precursor specifically selects the unspliced viral genomic RNA (gRNA) from the bulk of cellular and spliced viral RNAs via its nucleocapsid (NC) domain and drives gRNA encapsidation at the plasma membrane (PM). To further identify the determinants governing the intracellular trafficking of Gag-gRNA complexes and their accumulation at the PM, we compared, in living and fixed cells, the interactions between gRNA and wild-type (WT) Gag or Gag mutants carrying deletions in NC zinc fingers (ZFs), or a non-myristoylated version of Gag. Our data showed that the deletion of both ZFs simultaneously or the complete NC domain completely abolished intracytoplasmic Gag-gRNA interactions. Deletion of either ZF delayed the delivery of gRNA to the PM but did not prevent Gag-gRNA interactions in the cytoplasm, indicating that the two ZFs display redundant roles in this respect. However, ZF2 played a more prominent role than ZF1 in the accumulation of the ribonucleoprotein complexes at the PM. Finally, the myristate group which is mandatory for anchoring the complexes at the MP, was found to be dispensable for the association of Gag with the gRNA in the cytosol. STATEMENT of SIGNIFICANCEFormation of HIV-1 retroviral particles relies on specific interactions between the retroviral Gag precursor and the unspliced genomic RNA (gRNA). During the late phase of replication, Gag orchestrates the assembly of newly formed viruses at the plasma membrane (PM). It has been shown that the intracellular HIV-1 gRNA recognition is governed by the two-zinc finger (ZF) motifs of the nucleocapsid (NC) domain in Gag. Here we provided a clear picture of the role of ZFs in the cellular trafficking of Gag-gRNA complexes to the PM by showing that either ZF was sufficient to efficiently promote these interactions in the cytoplasm, while interestingly, ZF2 played a more prominent role in the relocation of these ribonucleoprotein complexes at the PM assembly sites.

biophysics↗