Genomic sequences homologous to the protein kinase region of the bifunctional herpes simplex virus type 2 protein ICP10

Targeting apoptosis in neurological disease using the herpes simplex virus

Herpes Simplex Viruses type 1 (HSV-1) and 2 (HSV-2) cause central nervous system (CNS) disease ranging from benign aseptic meningitis to fatal encephalitis. In adults, CNS infection with HSV-2 is most often associated with aseptic meningitis while HSV-1 frequently produces severe, focal encephalitis associated with high mortality and morbidity. Recent studies suggested that the distinct neurological outcome of CNS infection with the two viruses may be due to their distinct modulation of apoptotic cell death: HSV-1 triggers neuronal apoptosis, while HSV-2 is neuroprotective. Apoptosis also occurs in the etiology of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Down's syndrome, and determines the loss of specific neuronal populations and the decline in cognitive functions. Notwithstanding, the therapy of these disorders may rely on the use of replication-defective HSV-1 vectors to deliver anti-apoptotic transgenes to the CNS. However, the recent discovery of a neuroprotective activity innate to the HSV-2 genome (the ICP10 PK gene) suggests that: i) ICP10 PK may constitute a novel therapeutic approach by targeting both the apoptotic cell death and the cognitive decline, and ii) HSV-2 may be more suitable than HSV-1 as a vector for targeting neuronal disease.

A growth and latency compromised herpes simplex virus type 2 mutant (ICP10DeltaPK) has prophylactic and therapeutic protective activity in guinea pigs

A growth compromised herpes simplex virus type 2 (HSV-2) mutant which is deleted in the PK domain of the large subunit of ribonucleotide reductase (ICP10DeltaPK) protects from fatal HSV-2 challenge in the mouse model (Aurelian L, Kokuba H, Smith CC. Vaccine potential of a Herpes Simplex Virus type 2 mutant deleted in the PK domain of the large subunit of ribonucleotide reductase (ICP10). Vaccine 1999;17:1951-1963). Here we report the results of our studies with ICP10DeltaPK in the guinea pig model of recurrent HSV-2 disease. ICP10DeltaPK was also compromised for growth and disease causation in this model. It was not isolated from latently infected ganglia by explant co-cultivation. The proportions of latently infected ganglia were significantly lower for ICP10DeltaPK than HSV-2 [3/25 (12%) and 7/10 (70%), respectively]. Similar results were obtained for the levels of viral DNA (8 x 10(3) and 2 x 10(5) molecules/ganglion for ICP10DeltaPK and HSV-2, respectively]. ICP10DeltaPK immunization caused a significant (P< or = 0.001) decrease in the proportion of animals with primary [1/14 (6%) and 16/16 (100%) for ICP10DeltaPK and PBS, respectively) and recurrent [1/14 (6%) and 11/14 (79%) for ICP10DeltaPK and PBS, respectively) HSV-2 skin lesions. It also protected from genital HSV-2 disease [1/10 and 10/10 for ICP10DeltaPK and PBS, respectively] and decreased the severity of the lesions in both models. Quantitative PCR (Q-PCR) with primers that distinguish between HSV-2 and ICP10DeltaPK indicated that immunization reduced the proportion of ganglia positive for HSV-2 DNA [8/25 (32%) and 7/10 (70%) for ICP10DeltaPK and PBS, respectively) and its levels [3 x 10(3) and 2 x 10(5) molecules/ganglion for ICP10DeltaPK and PBS, respectively]. The proportion of HSV-2 infected animals with recurrent disease was also significantly (P < or = 0.001) decreased by immunization with ICP10DeltaPK [1/15 (7%) and 11/14 (79%) with recurrent disease for ICP10DeltaPK and PBS, respectively], suggesting that ICP10DeltaPK has prophylactic and therapeutic activity in the guinea pig.

A novel gene expressed in human keratinocytes with long-term in vitro growth potential is required for cell growth

The herpes simplex virus large subunit of ribonucleotide reductase differs from its counterparts in eukaryotic and prokaryotic cells and in other viruses in that it contains a unique domain that codes for a distinct serine-threonine protein kinase that activates the Ras/MEK/MAPK mitogenic pathway and is required for virus growth. Previous studies suggested that ribonucleotide reductase protein kinase was co-opted from a cellular gene. Cellular genes similar to ribonucleotide reductase protein kinase were not cloned, however, and their function is unknown. Here we report that a novel gene (H11) that codes for a protein similar to herpes simplex virus 2 ribonucleotide reductase protein kinase, is expressed in skin tissues, cultured keratinocytes, and the keratinocyte cell line A431. The protein is phosphorylated and it associates with the plasma membrane. H11 is expressed in keratinocytes with long-term in vitro growth potential and is coexpressed with high levels of adhesion molecules involved in signal transduction, such as beta1 integrin. Antisense oligonucleotides that inhibit H11 expression inhibit DNA synthesis and keratinocyte proliferation, suggesting that H11 expression is required for cell growth.

A novel human gene similar to the protein kinase (PK) coding domain of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10) codes for a serine-threonine PK and is expressed in melanoma cells

The large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10) is a multifunctional protein that contains a serine-threonine protein kinase (PK) activity (Nelson, J. W., Zhu, J. , Smith, C. C., Kulka, M., and Aurelian, L. (1996) J. Biol. Chem. 271, 17021-17027). Phylogenetic analyses indicated that ICP10 PK belongs to a distinct subfamily of growth factor receptor serine-threonine PKs that are characterized by their ability to function with a limited number of conserved catalytic motifs (Hunter, J. C. R., Smith, C. C., and Aurelian, L. (1995) Int. J. Onc. 7, 515-522). Here, we report the isolation and characterization of a novel gene, designated H11, that contains an open reading frame of 588 nucleotides, which encodes a protein similar to ICP10 PK. The H11 protein has Mn(2+)-dependent serine-threonine-specific PK activity as determined with a GST-H11 fusion protein and by immununocomplex PK/immunoblotting assays of 293 cells transfected with a H11 eukaryotic expression vector. PK activity is ablated by mutation of Lys(113) within the presumtive catalytic motif II (invariant Lys). 293 cells stably transfected with H11 acquire anchorage-independent growth. Endogenous H11 RNA and the H11 phosphoprotein are expressed in melanoma cell lines and primary melanoma tissues at levels higher than in normal melanocytes and in benign nevi. Melanoma cell proliferation is inhibited by treatment with antisense oligonucleotides that inhibit H11 translation, suggesting that H11 expression is associated with cell growth.

The PK domain of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10) is required for immediate-early gene expression and virus growth

The large subunit of herpes simplex virus (HSV) ribonucleotide reductase (RR), RR1, contains a unique amino-terminal domain which has serine/threonine protein kinase (PK) activity. To examine the role of the PK activity in virus replication, we studied an HSV type 2 (HSV-2) mutant with a deletion in the RR1 PK domain (ICP10DeltaPK). ICP10DeltaPK expressed a 95-kDa RR1 protein (p95) which was PK negative but retained the ability to complex with the small RR subunit, RR2. Its RR activity was similar to that of HSV-2. In dividing cells, onset of virus growth was delayed, with replication initiating at 10 to 15 h postinfection, depending on the multiplicity of infection. In addition to the delayed growth onset, virus replication was significantly impaired (1,000-fold lower titers) in nondividing cells, and plaque-forming ability was severely compromised. The RR1 protein expressed by a revertant virus [HSV-2(R)] was structurally and functionally similar to the wild-type protein, and the virus had wild-type growth and plaque-forming properties. The growth of the ICP10DeltaPK virus and its plaque-forming potential were restored to wild-type levels in cells that constitutively express ICP10. Immediate-early (IE) genes for ICP4, ICP27, and ICP22 were not expressed in Vero cells infected with ICP10DeltaPK early in infection or in the presence of cycloheximide, and the levels of ICP0 and p95 were significantly (three- to sevenfold) lower than those in HSV-2- or HSV-2(R)-infected cells. IE gene expression was similar to that of the wild-type virus in cells that constitutively express ICP10. The data indicate that ICP10 PK is required for early expression of the viral regulatory IE genes and, consequently, for timely initiation of the protein cascade and HSV-2 growth in cultured cells.

Cervical cancer: is herpes simplex virus type II a cofactor?

In many ways, cervical cancer behaves as a sexually transmitted disease. The major risk factors are multiple sexual partners and early onset of sexual activity. Although high-risk types of human papillomaviruses (HPV) play an important role in the development of nearly all cases of cervical cancer, other sexually transmitted infectious agents may be cofactors. Herpes simplex virus type 2 (HSV-2) is transmitted primarily by sexual contact and therefore has been implicated as a risk factor. Several independent studies suggest that HSV-2 infections correlate with a higher than normal incidence of cervical cancer. In contrast, other epidemiological studies have concluded that infection with HSV-2 is not a major risk factor. Two separate transforming domains have been identified within the HSV-2 genome, but continued viral gene expression apparently is not necessary for neoplastic transformation. HSV infections lead to unscheduled cellular DNA synthesis, chromosomal amplifications, and mutations. These observations suggest that HSV-2 is not a typical DNA tumor virus. It is hypothesized that persistent or abortive infections induce permanent genetic alterations that interfere with differentiation of cervical epithelium and subsequently induce abnormal proliferation. Thus, HSV-2 may be a cofactor in some but not all cases of cervical cancer.

Immediate early and functional AP-1 cis-response elements are involved in the transcriptional regulation of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10)

Expression from the promoter of the herpes simplex virus type 2 (HSV-2) large subunit of ribonucleotide reductase (ICP10) is stimulated by co-transfection with DNA that encodes the virion protein Vmw65 previously shown to activate in trans the transcription of all IE genes (Wymer et al., 1989). Specific cis response elements involved in ICP10 transcriptional regulation were studied by chloramphenicol acetyltransferase analysis with hybrid ICP10 promoter/CAT structural gene constructions containing wild type or site-directed mutations of the promoter sequences. The data indicate that Vmw65 activation requires an intact TAAT-GARAT motif while complex formation requires an intact Oct-1 element, and the AP-1 consensus elements in the ICP10 promoter are functional in vitro. Thus, expression from the wild type and GA-rich mutant constructions was enhanced 10-20-fold by co-transfection with DNA encoding Vmw65. The GARAT and POU homeobox (PHB) binding motifs were required for Vmw65 mediated activation but the mutant in the POU specific box (PSB) binding motif was activated at higher concentrations of Vmw65 DNA (1.0-3.0 micrograms). The PHB and PSB binding motifs were necessary for complex formation as determined by gel retardation analysis with in vitro synthesized OTF-1 and Vmw65 proteins. The GARAT and GA-rich elements were not required. CAT expression from pICP10-cat was enhanced by co-transfection with jun and fos encoding DNA, and the ICP10 promoter complexed with in vitro synthesized jun protein.