The HIV-1 Nucleocapsid Regulates Its Own Condensation by Phase-Separated Activity-Enhancing Sequestration of the Viral Protease during Maturation

Abstract

A growing number of studies indicate that mRNAs and long ncRNAs can affect protein populations by assembling dynamic ribonucleoprotein (RNP) granules. These phase-separated molecular ‘sponges’, stabilized by quinary (transient and weak) interactions, control proteins involved in numerous biological functions. Retroviruses such as HIV-1 form by self-assembly when their genomic RNA (gRNA) traps Gag and GagPol polyprotein precursors. Infectivity requires extracellular budding of the particle followed by maturation, an ordered processing of ∼2400 Gag and ∼120 GagPol by the viral protease (PR). This leads to a condensed gRNA-NCp7 nucleocapsid and a CAp24-self-assembled capsid surrounding the RNP. The choreography by which all of these components dynamically interact during virus maturation is one of the missing milestones to fully depict the HIV life cycle. Here, we describe how HIV-1 has evolved a dynamic RNP granule with successive weak–strong–moderate quinary NC-gRNA networks during the sequential processing of the GagNC domain. We also reveal two palindromic RNA-binding triads on NC, KxxFxxQ and QxxFxxK, that provide quinary NC-gRNA interactions. Consequently, the nucleocapsid complex appears properly aggregated for capsid reassembly and reverse transcription, mandatory processes for viral infectivity. We show that PR is sequestered within this RNP and drives its maturation/condensation within minutes, this process being most effective at the end of budding. We anticipate such findings will stimulate further investigations of quinary interactions and emergent mechanisms in crowded environments throughout the wide and growing array of RNP granules.

Influence of HIV-1 genomic RNA on the formation of Gag biomolecular condensates

“…Interestingly, disorder was higher in both the RNA-binding MA highly basic region (MA-HBR) (i.e., 70.00%) [51] and RNA-binding NC ZnFs (48.57%). Although the NC domain of Gag contributes to phase separation and can itself produce large cytoplasmic aggregates within stress granules [44,45,60,61], the MA domain has yet to be shown to contribute to phase separation of Gag. However, a number of studies have shown that MA forms trimers [62][63][64], and that MA alone can produce VLPs [65,66], suggesting that, similar to NC, the mature MA protein participates in protein-protein interactions.…”

Biomolecular condensates: insights into early and late steps of the HIV-1 replication cycle

“…The plasticity of BMCs should seamlessly orchestrate various replication steps (Fig. 1), especially enzymatic activities (e.g., PR, RT, IN) [112] and may allow for virus-host assemblies and interactions through engagement and disengagement [137] that are obligatory throughout the replication cycles of retroviruses and other viruses.…”

“…Processing of pr55Gag in cells with a recombinant and active viral protease resulted in abundant mobile, condensates in cells [92]. While NC was shown to co-assemble PR-containing condensates late at the end of budding, in elegant work [112], NC condensates exhibited strong "scaffolding" activity in this context (Fig. 9 and Table 1), with the core proteins RT, IN, PR (and the viral genomic RNA) as clients, relying on the scaffolding behaviour of HIV-1 NC in cells [92] consistent with work from the Lyonnais and Mirambeau labs [112] and predicted high capacity to form droplets (p LLPS = 0.6502, Fig.…”

Effect of Twin Spacing and Loading Mode on Mechanical Properties and Deformation Mechanism of NiCoAl Columnar Polycrystalline Alloy

“…The advantages of computational simulation, such as progressiveness and convenience, have led it to becoming rapidly developed and widely used. [ 9 ] Molecular dynamics can understand and verify the macroscopic performance by calculating the movement track of atoms or molecules at a certain time. Compared with other simulation methods, molecular dynamics has strong advantages in many aspects.…”