HIV1 Vpr Arrests the Cell Cycle by Recruiting DCAF1/VprBP, a Receptor of the Cul4-DDB1 Ubiquitin Ligase

Abstract

How the HIV1 Vpr protein initiates the host cell response leading to cell cycle arrest in G(2) has remained unknown. Here, we show that recruitment of DCAF1/VprBP by Vpr is essential for its cytostatic activity, which can be abolished either by single mutations of Vpr that impair DCAF1 binding, or by siRNA-mediated silencing of DCAF1. Furthermore, DCAF1 bridges Vpr to DDB1, a core subunit of Cul4 ubiquitin ligases. Altogether these results point to a mechanism where Vpr triggers G(2) arrest by hijacking the Cul4/DDB1(DCAF1) ubiquitin ligase. We further show that, Vpx, a non-cytostatic Vpr-related protein acquired by HIV2 and SIV, also binds DCAF1 through a conserved motif. Thus, Vpr from HIV1 and Vpx from SIV recruit DCAF1 with different physiological outcomes for the host cell. This in turn suggests that both proteins have evolved to preserve interaction with the same Cul4 ubiquitin ligase while diverging in the recognition of host substrates targeted for proteasomal degradation.

Lentiviral Vpr usurps Cul4–DDB1[VprBP] E3 ubiquitin ligase to modulate cell cycle

“…DDB1, in turn, connects them to Cul4. Thus, by analogy to these polypeptides, VprBP probably functions as a substrate receptor for Cul4 (17,26,38). Importantly, our data show that Vpr positively regulates the ubiquitin ligase activity of this specific E3 complex probably by elevating neddylation of Cul4.…”

“…ATR triggers checkpoint signaling on genotoxic stress to stop the progression of the cell cycle until the damaged DNA is repaired (15). Recent evidence suggests that Vpr leads to ATR activation by interfering with the DNA replication machinery of the infected cell (16) and implicates Cullin 4 ubiquitin ligase containing VprBP/DCAF1 as potentially important for this effect (17,18). It should be pointed out, however, that Vpr was also reported to interact with signaling molecules downstream of ATR, such as 14-3-3 proteins and Cdc25C, raising the possibility that additional mechanisms may be usurped by the viral protein to perturb the progression of the cell cycle (19)(20)(21).…”

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

“…We first examined which cellular proteins are modulated on HIV-1 Vpr delivery in HeLa cells. These cells represent a convenient model to perform a SILAC analysis, and Vpr is known to be active in HeLa cells, promoting, for instance, cell cycle arrest (26). To this aim, VLPs containing WT Vpr or a G2 arrest-defective Vpr mutant (Vpr S79A), both tagged with an HA epitope, or Vpr-negative (empty) VLPs were delivered to HeLa cells stably labeled respectively with light, medium, or heavy isotopes (Fig.…”

“…First, the best renowned activity of Vpr, its ability to mediate a G2 arrest of the cell cycle, depends on the activation of the ATR-mediated (ATR: ataxia telangiectasia mutated and Rad3 related) DNA damage response (22). G2 arrest requires Vpr binding to DCAF1, an adaptor of the Cul4A-DDB1 ubiquitin ligase, which is involved in DNA repair in noninfected cells (23)(24)(25)(26)(27)(28)(29). More recently, Vpr has been shown to activate the SLX4 complex (SLX4com) with the help of DCAF1 (21,30).…”

VprBP targets Merlin to the Roc1-Cul4A-DDB1 E3 ligase complex for degradation

“…One of these WD40 domain-containing proteins, VprBP/ DCAF1, contains four WD40 domains and a LisH domain. VprBP was originally identified due to its interaction with the Vpr protein from the human immunodeficiency virus, however, the physiological function and substrates of VprBP/DCAF1 are still unknown (Zhang et al, 2001;Belzile et al, 2007;Hrecka et al, 2007;Le Rouzic et al, 2007;Tan et al, 2007;Wen et al, 2007).…”