Herpes simplex virus type 1 ICP27 is an essential regulatory protein

We previously reported that herpes simplex virus type 1 (HSV-1) can activate the stress-activated protein kinases (SAPKs) p38 and JNK. In the present study, we undertook a comprehensive and comparative analysis of the requirements for viral protein synthesis in the activation of JNK and p38. Infection with the UL36 mutant tsB7 or with UV-irradiated virus indicated that both JNK The stress-activated protein kinases (SAPKs) p38 and JNK are part of a larger family of serine/threonine terminal kinases termed mitogen-activated protein kinases (MAPK), which includes ERK1 and -2. SAPK pathways are normally activated by UV irradiation, anoxia, and engagement of proinflammatory cytokines or Fas ligand by their cognate receptors. Following ligand binding to a cognate receptor, signaling is initiated through receptor-associated kinases to a MAPKKK (MAPK kinase kinase). MAPKKKs capable of initiating the p38 or JNK pathway include MEKK1, -2, -3, and -4, ASK-1, TAK-1, and TAO. These in turn activate dual-specificity MAPK kinase kinases (MAPKKs) MKK3/6 and MKK4/7, which directly bind and phosphorylate p38 and JNK, respectively, on both tyrosine and threonine, resulting in their activation (for a review, see reference 78).All three subfamilies of human herpesviruses activate one or more of the MAPKs during infection. The betaherpesvirus cytomegalovirus activates both p38 and ERK by a mechanism dependent on viral gene expression (14,39,76) and the upstream kinases MKK3/6 and MKK1/2, respectively, (39, 40). ERK activates the early gene UL112-113 promoter (76) and phosphorylates immediate-early 86 and 72 proteins to alter their transactivation activity (40), while p38 phosphorylates retinoblastoma protein and HSP27 (39). ERK and p38 activation are required for cytomegalovirus DNA replication (16). The gammaherpesvirus Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor activates ERK and p38, causing increased vascular endothelial growth factor expression via phosphorylation of hypoxia-inducible factor 1␣ (86). The gammaherpesvirus Epstein-Barr virus activates p38 and JNK (1, 21). The immediate-early proteins BZLF1 and BRLF1 induce increased phosphorylation of p38 and JNK and activation of the ATF-2 transcription factor (1). BZLF1 expression during BRLF1-driven virus reactivation requires p38 activity (1). Among the alphaherpesviruses, HSV-2 has been reported to activate ERK through ICP10-PK binding to RAS-GAP, leading to further expression of ICP10 and prevention of apoptosis (68).Two previous reports documented the activation of the p38 and JNK (SAPK) pathways by HSV-1. Increased JNK and p38 kinase activity was observed as early as 3 hours postinfection and remained active throughout the course of infection (56,97). SAPKs were activated downstream of Ras, as infection with a dominant-negative form of Ras did not affect activation of the transcription factors ATF-2 and c-Jun, downstream targets of p38 and JNK, respectively (56). Furthermore, activation was specific for SAPKs, as ERK was not activated during infect...

“…As previously observed by others, vBSLG4 expressed greatly reduced levels of gC (Fig. 7A, lanes 11 to 12) (79).…”

Section: Fig 2 Infection With Uv-irradiated Hsv Does Not Results In supporting

confidence: 88%

Section: Fig 2 Infection With Uv-irradiated Hsv Does Not Results In mentioning

confidence: 99%

Herpes Simplex Virus ICP27 Activation of Stress Kinases JNK and p38

Hargett¹,

McLean²,

Bachenheimer

2005

“…FI-14 cells (VZV ORF62-expressing Vero cells [15]) and 3-3 cells (HSV-1 ICP27-expressing Vero cells [24]), provided by Priscilla A. Schaffer, were propagated as previously described. HSV-1 7134 (an ICPO null mutant [3]), HSV-1 Sdll.2 (an ICP27 deletion mutant [32]), and d120 (an HSV-1 ICP4 deletion mutant [9]) were provided by Priscilla A. Schaffer. These HSV-1 mutants were all derived from the KOS strain.…”

Section: Methodsmentioning

confidence: 99%

Varicella-zoster virus open reading frame 61 protein is functionally homologous to herpes simplex virus type 1 ICP0

Moriuchi

Smith

et al. 1992

The varicella-zoster virus (VZV) open reading frame 61 (ORF61) protein is thought to be the homolog of herpes simplex virus type 1 (HSV-1) ICPO, based on gene location and limited amino acid homology. However, HSV-1 ICPO trans activates HSV-1 genes, while VZV ORF61 protein trans represses the function of VZV trans activators on VZV promoters in transient expression assays. To investigate the functional relatedness of HSV-1 ICPO and VZV ORF61 protein, we established Vero and MeWo cell lines which stably express VZV ORF61 under the control of a metallothionein promoter and performed complementation studies with an HSV-1 ICPO deletion mutant (7134). Mutant 7134 is impaired for plaque formation and replication at a low multiplicity of infection in cell culture, but these defects were complemented by up to 200-fold in Vero cell lines expressing VZV ORF61. Likewise, the efficiency of plaque formation was improved by up to 100-fold in MeWo cell lines expressing VZV ORF61. A cell line expressing another VZV immediate-early gene product (0RF62) was unable to complement mutant 7134. HSV-1 mutants which are deleted for other HSV-1 immediate-early gene products (ICP4, ICP27) were unable to grow in VZV ORF61-expressing cell lines. These results indicate that, despite marked differences in their sequences and in effects on their cognate promoters in transient expression assays, VZV ORF61 protein is the functional homolog of HSV-1 ICPO.

“…During productive infection, the expression of herpes simplex virus type 1 (HSV-1) genes is regulated by four virusencoded nuclear-phosphoproteins, ICPs 0, 4, 22, and 27 (2,8,12,22,24,46,56,57,61,63,64,66,68,71). The genes for these proteins, termed immediate-early genes, are the first of over 70 viral genes to be expressed in virus-infected cells.…”

mentioning

confidence: 99%

An activity specified by the osteosarcoma line U2OS can substitute functionally for ICP0, a major regulatory protein of herpes simplex virus type 1

Yao

Schaffer

1995

Self Cite

164

Among the five immediate-early regulatory proteins of herpes simplex virus (HSV) type 1, only ICP0 is capable of activating all kinetic classes of viral genes. Consistent with its broad transactivating activity, ICP0 plays a major role in enhancing the reactivation of HSV from latency both in vivo and in vitro. Although not essential for viral replication, ICP0 confers a significant growth advantage on the virus, especially at low multiplicities of infection. In this report we describe the expression of a novel activity by the osteosarcoma cell line U2OS that can substitute functionally for ICP0. Compared with Vero cells, both U2OS cells and cells of the ICP0-expressing line 0-28 significantly enhanced the plating efficiency of an ICP0 null mutant, 7134. In contrast, the plating efficiencies of the wild-type virus in all three cell types were similar. Single-step growth experiments demonstrated that the yield of 7134 in U2OS cells was severalfold higher than that in 0-28 cells and about 100-fold higher than that in Vero cells. In order to identify the viral genes whose expression is enhanced by the activity in U2OS cells, levels of expression of selected viral proteins in extracts of Vero and U2OS cells were compared by Western blot (immunoblot) analysis following low-multiplicity infection. At a multiplicity of 0.1 PFU per cell, the levels of expression of the immediate-early protein ICP4 and the early protein gD in 7134-infected U2OS cells were significantly higher than those in 7134-infected Vero cells. When infections were carried out at a multiplicity of 1 PFU per cell, however, no major differences in the levels of expression of these proteins in U2OS and Vero cells were observed. Cycloheximide reversal experiments demonstrated that the cellular activity expressed in U2OS cells that promotes high-level expression of ICP4 is not synthesized de novo but appears to exist as a preformed protein(s). To confirm this observation and to determine whether, like immediate-early genes, early, delayed-early, and late viral genes are also responsive to the cellular activity, transient-expression assays were performed. The results of these tests demonstrated that basal levels of expression from immediate-early, early, and delayed-early promoters, but not that from a late promoter, were significantly higher in U2OS cells than in Vero cells and that this enhancement occurred in the absence of viral proteins. Mutational analysis of the ICP4 promoter, the most responsive of the HSV type 1 promoters tested, has shown that the 139-bp sequence between the SphI and SacII sites is required for the high basal level of expression of ICP4 in U2OS cells.