Herpes Simplex Virus Type 1 Immediate-Early Protein Vmw110 Induces the Proteasome-Dependent Degradation of the Catalytic Subunit of DNA-Dependent Protein Kinase

Abstract

Herpes simplex virus type 1 (HSV-1) infection causes the active degradation of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), and this process is reliant on the expression of the HSV-1 immediate-early protein Vmw110. In this study we investigated in more detail the mechanism by which the degradation occurs, the domains of Vmw110 which are required, and whether Vmw110 is by itself sufficient for the effect. We found that proteasome inhibitors prevented the degradation of DNA-PKcs, indicating the involvement of a proteasome pathway. Furthermore, the continued activity of DNA-PK during infection in the presence of these inhibitors indicated that Vmw110 does not directly alter the enzyme activity of DNA-PKcs prior to its degradation in a normal infection. Indeed, Vmw110 was found to bind to neither the catalytic nor Ku subunits of DNA-PK. Using mutant Vmw110 viruses we show that the RING finger domain of Vmw110 is essential for the induced degradation of DNA-PKcs but that the ability of Vmw110 to bind to a cellular ubiquitin-specific protease (HAUSP) is not required. When expressed in the absence of other viral proteins, Vmw110 was sufficient to cause the degradation of DNA-PKcs, indicating that the effect on the stability of DNA-PKcs was a direct consequence of Vmw110 activity and not an indirect Vmw110-dependent effect of virus infection. Finally, the Vmw110-induced degradation of DNA-PKcs and loss in DNA-PK activity appears to be beneficial to HSV-1 infection, as virus replication was more efficient in cells lacking DNA-PKcs, especially at low multiplicities of infection.

Proteomic analysis by iTRAQ in red claw crayfish, Cherax quadricarinatus, hematopoietic tissue cells post white spot syndrome virus infection

“…Recently a plethora of viral proteins have been shown to direct host-cell proteins for proteolytic degradation. These activities are required for various aspects of viral life cycle like viral entry [38], replication [39], enhanced survival [40,41], and to viral release [42]. Similar to our study, infection of enterovirus 61 in rhabdomyosarcoma cells resulted in down-regulation of proteasome subunit alpha type 2 [43].…”

West Nile virus genome amplification requires the functional activities of the proteasome

“…Mouse hepatitis virus (a coronovirus) and minute virus (a parvovirus) have also been shown to utilize the proteasome system for trafficking to the cytoplasm (Yu and Lai, 2005) or the nucleus (Ros et al, 2002;Ros and Kempf, 2004), respectively. Multiple members of the Herpesviridae family have evolved different mechanisms to manipulate the ubiquitin-proteasome pathway, whether it is by encoding ubiquitin ligaselike proteins (Coscoy et al, 2001) or by targeting specific proteins for destruction (Coscoy et al, 2001;Kikkert et al, 2001;Parkinson et al, 1999;Prosch et al, 2003). Inhibition of proteasome activity was shown to impair coxsackievirus B3 replication (Luo et al, 2003).…”

Changing the ubiquitin landscape during viral manipulation of the DNA damage response

“…DNA-PKcs and DNA ligase IV have also been proposed to play roles in circularization or processing of HSV-1 genomes. While DNA ligase IV/XRCC4 dependent processing has been proposed to benefit viral replication [80], DNA-PKcs inhibits viral replication and is targeted for degradation by ICP0 [81]. The significance of ICP0-mediated targeting of DNA-PKcs is unclear, although expression of ICP0 inhibited the formation of circular genomes at early times post-infection, raising the possibility that DNA-PKcs may normally serve to circularize incoming viral genomes [82].…”