Martins, L. J. | bioRxiv Science

bioRxiv2021

HIV-1 Vpr Induces Degradation of Nucleolar Protein CCDC137 as a Consequence of Cell Cycle Arrest

Expression of HIV-1 accessory proteins Vif and Vpr results in G2/M cell cycle arrest by hijacking the host ubiquitin-proteasome system. Vif directs cell cycle arrest by targeting protein phosphatase 2, regulatory subunit B alpha (PP2AB56) for degradation. However, the ubiquitination target(s) of Vpr that is directly responsible for G2/M arrest has remained elusive. Recently, Vpr directed degradation of nucleolar protein coiled-coil domain containing 137 (CCDC137), also known as retinoic acid resistance factor (RaRF), has been implicated as the proximal event leading to G2/M cell cycle arrest. In this study we aimed to further investigate this finding. We confirm that CCDC137 is targeted for degradation in the presence of Vpr with a requirement for the CUL4ADDB1.DCAF1 E3 ligase complex. However, degradation of CCDC137 is a general consequence, rather than a trigger, of G2/M arrest. Thus, whether induced by Vpr expression or pharmacologically via CDK1 inhibition, G2/M blockade results in degradation of CCDC137. Furthermore, siRNA-mediated depletion of CCDC137 failed to induce G2/M arrest.

microbiology↗

bioRxiv2017

Histone deacetylase inhibition reduces deleterious cytokine release induced by ingenol stimulation

IntroductionLatency reversal agents (LRAs), such as protein kinase C (PKC) agonists, constitute a promising strategy for exposing and eliminating the HIV-1 latent reservoir. PKC agonists activate NF-{kappa}B and, in turn, induce deleterious pro-inflammatory cytokine production. Adjuvant pharmacological agents, such as ruxolitinib, a JAK inhibitor, and rapamycin, an mTOR inhibitor, have previously been combined with LRAs to reduce deleterious pro-inflammatory cytokine secretion without inhibiting HIV-1 viral reactivation in vitro. Histone deacetylase inhibitors (HDACi) are known to dampen pro-inflammatory cytokine secretion in the context of other diseases and can synergize with other LRAs to bring dormant proviruses out of latency. In this study we investigated whether a broad panel of epigenetic modifiers, including HDACi, could effectively dampen PKC-induced pro-inflammatory cytokine secretion during latency reversal. MethodsWe screened an epigenetic modifier library to identify compounds that reduced intracellular IL-6 production induced by the PKC agonist Ingenol-3,20-dibenzoate. We further tested the most promising epigenetic inhibitor class, HDACi, for their ability to reduce a broad panel of pro-inflammatory cytokines and reactivate latent HIV-1 ex vivo. ResultsWe identified nine epigenetic modulators that reduced PKC-induced intracellular IL-6. In cells from aviremic individuals living with HIV-1, the HDAC1-3 inhibitor, suberohydroxamic acid (SBHA), reduced secretion of pro-inflammatory cytokines TNF-, IL-5, IL-2r, and IL-17 but did not significantly reactivate latent HIV-1 when used in combination with Ingenol-3,20-dibenzoate. ConclusionThe addition of SBHA to Ingenol-3,20-dibenzoate reduces deleterious cytokine production during latency reversal but does not induce significant viral reactivation in aviremic donor PBMCs. The ability of SBHA to reduce PKC-induced pro-inflammatory cytokines when used in combination with Ingenol-3,20-dibenzoate suggests that SBHA can be used to reduced PKC induced pro-inflammatory cytokines but not to achieve latency reversal in the context of HIV-1.

microbiology↗