PML Contributes to a Cellular Mechanism of Repression of Herpes Simplex Virus Type 1 Infection That Is Inactivated by ICP0

Abstract

Promyelocytic leukemia (PML) nuclear bodies (also known as ND10) are nuclear substructures that contain several proteins, including PML itself, Sp100, and hDaxx. PML has been implicated in many cellular processes, and ND10 are frequently associated with the replicating genomes of DNA viruses. During herpes simplex virus type 1 (HSV-1) infection, the viral regulatory protein ICP0 localizes to ND10 and induces the degradation of PML, thereby disrupting ND10 and dispersing their constituent proteins. ICP0-null mutant viruses are defective in PML degradation and ND10 disruption, and concomitantly they initiate productive infection very inefficiently. Although these data are consistent with a repressive role for PML and/or ND10 during HSV-1 infection, evidence in support of this hypothesis has been inconclusive. By use of short interfering RNA technology, we demonstrate that depletion of PML increases both gene expression and plaque formation by an ICP0-negative HSV-1 mutant, while having no effect on wild-type HSV-1. We conclude that PML contributes to a cellular antiviral repression mechanism that is countered by the activity of ICP0.Promyelocytic leukemia (PML) nuclear bodies (also known as ND10) are discrete nuclear substructures that are defined by the presence of the promyelocytic leukemia protein, PML. ND10 have been implicated in a great variety of processes, including oncogenesis, apoptosis, viral infection, the stress and interferon responses, DNA repair, the regulation of gene expression, and certain aspects of chromatin structure (for reviews see references 2, 3, 8, 28, and 45). ND10 become intricately associated with the parental genomes of nuclear-replicating DNA viruses, and they are modified by several viral regulatory proteins; structural modification of ND10 induced by these regulatory proteins frequently correlates with the efficiency of viral infection (for reviews, see references 9, 24, and 25). These observations have given rise to the hypothesis that ND10 structures have a repressive effect on viral infection, and viral regulatory proteins that disrupt these structures do so to relieve this repression. However, the evidence in support of this hypothesis is controversial.PML itself has been implicated in the regulation of infection by a variety of RNA viruses (34), adenoviruses (7, 35), and human cytomegalovirus (HCMV) (1). In the case of herpes simplex virus type 1 (HSV-1), the issues of the roles of PML protein and ND10 are complex. HSV-1 immediate-early regulatory protein ICP0 greatly increases the probability that the virus will enter lytic infection, and this activity correlates very well with ICP0-induced degradation of PML and disruption of ND10 (reviewed in references 10, 11, and 18). These observations have encouraged the hypothesis that PML and/or ND10 have a repressive effect on the development of lytic HSV-1 infection and that through its targeting of these structures ICP0 relieves this repression. Indeed, in the absence of ICP0, HSV-1 genomes have a greatly increased probability of ...

Nuclear Domain 10 Components Promyelocytic Leukemia Protein and hDaxx Independently Contribute to an Intrinsic Antiviral Defense against Human Cytomegalovirus Infection

“…Consequently, PML not only recruits the transcriptional repressor hDaxx to ND10 and thus sites of incoming viral genomes but also itself possesses the ability to suppress HCMV gene expression, although the exact mechanism of PML-mediated silencing remains to be determined. In summary, the results of our study further support the evolving concept that ND10 structures are part of an antiviral defense mechanism of the cell, with individual components of these structures contributing independently to counteract viral gene expression (14,15,43,48,50).…”

“…Similarly, plaque formation and IE gene expression of an ICP0-deficient herpes simplex virus type 1 was also shown to be enhanced in PML-negative fibroblasts (15), further supporting the notion of PML and ND10 as mediators of an intrinsic immune defense against herpesvirus infections in general. At the same time, the ND10 constituent hDaxx was identified as a repressor of HCMV IE gene expression and replication (8,45,46,50).…”

“…In PML-kd HFFs, which are devoid of putative ND10 structures, hDaxx can no longer be found in distinct foci but shows a dispersed distribution pattern throughout the nucleus (15,48). Since pp71 and hDaxx are known to directly interact in ND10 structures initially after infection of normal fibroblasts (21, 26, 36), this raised the interesting question of whether pp71 is still able to induce hDaxx degradation in PML-kd HFFs.…”

Progress and prospects: Biological properties and technological advances of herpes simplex virus type 1-based amplicon vectors

“…5 This protein has an E3 ubiquitin ligase activity that induces proteasomic degradation of several cellular proteins, including the promyelocytyc leukemia (PML) protein, and the disruption of PML bodies (also known as ND10), which are involved in repression of gene expression. 5 In the absence of ICP0, PML and PML bodies are preserved, and this correlates with decreased ability to start a lytic infection in human fibroblasts. 5 As amplicons do not express ICP0 or any other immediate-early protein, this inherent antiviral response may also be partially responsible for the silencing observed in some cell types.…”

“…5 In the absence of ICP0, PML and PML bodies are preserved, and this correlates with decreased ability to start a lytic infection in human fibroblasts. 5 As amplicons do not express ICP0 or any other immediate-early protein, this inherent antiviral response may also be partially responsible for the silencing observed in some cell types. Perhaps related to this hypothesis, it has been shown that the bacterial DNA sequences present in conventional amplicon vectors cause rapid transgene silencing by forming inactive chromatin in normal human fibroblasts.…”