The HIV-1 protein Vpr targets the endoribonuclease Dicer for proteasomal degradation to boost macrophage infection

Abstract

The HIV-1 protein Vpr enhances macrophage infection, triggers G2 cell cycle arrest, and targets cells for NK-cell killing. Vpr acts through the CRL4DCAF1 ubiquitin ligase complex to cause G2 arrest and trigger expression of NK ligands. Corresponding ubiquitination targets have not been identified. UNG2 and SMUG1 are the only known substrates for Vpr-directed depletion through CRL4DCAF1. Here we identify the endoribonuclease Dicer as a target of HIV-1 Vpr-directed proteasomal degradation through CRL4DCAF1. We show that HIV-1 Vpr inhibits short hairpin RNA function as expected upon reduction of Dicer levels. Dicer inhibits HIV-1 replication in T cells. We demonstrate that Dicer also restricts HIV-1 replication in human monocyte-derived macrophages (MDM) and that reducing Dicer expression in MDMs enhances HIV-1 infection in a Vpr-dependent manner. Our results support a model in which Vpr complexes with human Dicer to boost its interaction with the CRL4DCAF1 ubiquitin ligase complex and its subsequent degradation.

HIV-1 Vpr degrades the HLTF DNA translocase in T cells and macrophages

“…Surprisingly, HLTF was the sole cellular target that was clearly down-regulated in the presence of HIV-1 Vpr, among more than 2,000 proteins quantified. Several other host proteins have been proposed to be targeted by Vpr, but previous results were mostly based on candidate-based approaches and with often modest down-regulation (62)(63)(64). Importantly, HLTF is down-regulated by Vpr in infected T cells.…”

HIV-1 Vpr Protein Induces Proteasomal Degradation of Chromatin-associated Class I HDACs to Overcome Latent Infection of Macrophages

“…After 30 h, cells were harvested, and total RNA was extracted from 10 6 cells using RNeasy Mini Kit (Qiagen) according to the manufacturer's instructions. Using SuperScript II Reverse Transcriptase (Invitrogen) and oligo(dT) [12][13][14][15][16][17][18] Primers (Invitrogen), RNA was reverse transcribed into cDNA. The cDNA was diluted 100-fold with DNase-free water.…”

“…To analyze expression levels of HIV-1 mRNA in infected MDMs, total mRNA was extracted using Ultrasens Viral RNA kit (Qiagen) and reverse transcribed using SuperScript II Reverse Transcriptase and oligo(dT) [12][13][14][15][16][17][18] Primers. cDNA was then subjected to quantitative PCR using nuc-2-F and nuc-2-R primers.…”

“…Vpr enhances proteasomal degradation of the natural substrates of the Cul4-DDB1[VprBP] E3 ubiquitin ligase (8 -10). For instance, Vpr has been shown to enhance proteasomal degradation of UNG2 and dicer (11,12). These proteins are recruited by Vpr-binding protein (VprBP) 3 to the E3 ubiquitin ligase complexes as their natural substrates.…”

Cullin4A and Cullin4B Are Interchangeable for HIV Vpr and Vpx Action through the CRL4 Ubiquitin Ligase Complex

“…HIV-1 Vpr induces NK cell ligand expression on the surface of infected cells (98-100) as well as the depletion of the endoribonuclease Dicer (101,102). Both of these phenotypes require the function of the CRL4 complex.…”