Analysis of the Functions of Herpes Simplex Virus Type 1 Regulatory Protein ICP0 That Are Critical for Lytic Infection and Derepression of Quiescent Viral Genomes

Abstract

Herpes simplex virus type 1 (HSV-1) is an important human pathogen that infects the majority of the population at an early age and then establishes a life-long latent infection in sensory neurones. Periodic reactivation of latent virus causes episodes of active disease characterized by epithelial lesions at the site of the original primary infection. As with all herpesviruses, the ability of HSV-1 to establish and reactivate from latency is key to its clinical importance and evolutionary success. Therefore, the molecular mechanisms that regulate these processes have been the subject of intensive research (reviewed in reference 15). HSV-1 immediate-early (IE) protein ICP0 is required for efficient reactivation from latency in both mouse models and cultured cell systems of quiescent infection (15). ICP0 is also required to stimulate lytic infection by enhancing the probability that a cell receiving a viral genome will engage in productive infection (reviewed in references 19, 20 and 42). Therefore, a full understanding of the biology of HSV-1 infection requires a definition of the functions and mode of action of ICP0.The basic phenotype of ICP0-null mutant HSV-1 is a low probability of plaque formation, particularly in human diploid fibroblasts, that causes a high particle-to-PFU ratio (reference 20 and references therein). Biochemically, ICP0 is an E3 ubiquitin ligase of the RING finger class (4) that induces the degradation of several cellular proteins, including the promyelocytic leukemia (PML) protein (23), centromere proteins including CENP-C (54, 55), and the catalytic subunit of DNAprotein kinase (53,72). Among the consequences of these activities are the disruption of PML nuclear bodies (herein termed nuclear domain 10 [ND10]) (24, 58) and centromeres (54). ICP0 has also been reported to interact with histone deacetylase enzymes (HDACs) (56) and the CoREST repressor protein, thereby disrupting the CoREST/HDAC-1 complex (37, 39). Evidence has also been presented that expression of ICP0 correlates with increased acetylation of histones on viral chromatin (12). ICP0-null mutant viruses replicate less efficiently than the wild type (wt) in cells pretreated with interferon (IFN) (44,66), and there is evidence that ICP0 is able to impede an IFN-independent induction of IFN-stimulated genes that arises after infection with defective HSV-1 mutants (16,59,60,65,67,76). As a further complication, ICP0-null mutant HSV-1 replicates more efficiently in cells that have been highly stressed by a variety of treatments (5,6,79).On the basis of this evidence, several not necessarily mutually exclusive hypotheses have been put forward to explain the biological effects of ICP0. These include (i) that ICP0 counteracts an intrinsic cellular resistance mechanism that involves PML and other components of ND10, (ii) that ICP0 overcomes the innate cellular antiviral defense based on the IFN pathway, and (iii) that ICP0 counteracts the establishment of a repressed chromatin structure on the viral genome by interfering with histone d...

Equine herpesvirus type 1 replication is delayed in CD172a+ monocytic cells and controlled by histone deacetylases

“…and resulting in a productive EHV-1 infection in these cells. These results were consistent with recent work demonstrating the importance of protein acetylation and control of IE gene expression via HDACs during herpesvirus infections (Meier, 2001;Everett et al, 2009). In addition, we found that a higher number of CD172a + cells (12-14 %) were susceptible to EHV-1 infection following treatment with HDAC inhibitors compared with untreated cells (4 %).…”

Murine Cytomegalovirus Protein pM92 Is a Conserved Regulator of Viral Late Gene Expression

“…pYD-C618 was derived from pYD-C245 and carried the N-terminally 1ϫFLAG-tagged M92 coding sequence that was expressed together with DsRed as a bicistronic transcript. pYD-C755 (a gift from Roger Everett, University of Glasgow Center for Viral Research), pYD-C678, and pYD-C780 were pLKO.1-based lentiviral expression vectors that carried a puromycin resistance marker (23,24). Both pYD-C780 and pYD-C678 were derived from pYD-C755, and they carried the C-terminally 3ϫFLAG-tagged M92 and UL92 coding sequences, respectively.…”

APOBEC3A damages the cellular genome during DNA replication

“…Production of lentiviral particles was achieved by transfection of 293T cells as previously described. 67 Following transduction with the pSLIK-A3A lentivirus, cells were selected in 1 mg/mL neomycin. After selection, cells were maintained in 0.5 mg/mL neomycin.…”

“…HepaRG cells were a gift from R. Everett (University of Glasgow) and were grown as previously described. 67 Inducible HepaRG-A3A and U2OS-A3A cells were constructed using a dual vector system with pLKO-EGFP-TetR and pLKO-TetO-A3A as previously described. 37,67 To construct inducible AT22IJE-A3A cell lines, HA-tagged A3A cDNA was inserted into an entry vector with the CMV promoter and upstream Tetracycline Response Element (pEN_Tmcs).…”

“…67 Inducible HepaRG-A3A and U2OS-A3A cells were constructed using a dual vector system with pLKO-EGFP-TetR and pLKO-TetO-A3A as previously described. 37,67 To construct inducible AT22IJE-A3A cell lines, HA-tagged A3A cDNA was inserted into an entry vector with the CMV promoter and upstream Tetracycline Response Element (pEN_Tmcs). A pSLIK-A3A plasmid was generated by Gateway cloning of the pEN_Tmcs-A3A plasmid into a pSLIK lentivirus vector with a constitutively expressed neomycin resistance gene and tetracycline transactivator (rTA) 68 to generate a single vector system of doxycycline-inducible expression of A3A-HA.…”