The IE2 regulatory protein of human cytomegalovirus induces expression of the human transforming growth factor beta1 gene through an Egr-1 binding site

Potential utility of l-carnitine for preventing liver tumors derived from metabolic dysfunction-associated steatohepatitis

BACKGROUND

Recent reports have unveiled the potential utility of l-carnitine to alleviate metabolic dysfunction-associated steatohepatitis (MASH) by enhancing mitochondrial metabolic function. However, its efficacy at preventing the development of HCC has not been assessed fully.

METHODS

l-carnitine (2 g/d) was administered to 11 patients with MASH for 10 weeks, and blood liver function tests were performed. Five patients received a serial liver biopsy, and liver histology and hepatic gene expression were evaluated using this tissue. An atherogenic plus high-fat diet MASH mouse model received long-term l-carnitine administration, and liver histology and liver tumor development were evaluated.

RESULTS

Ten-week l-carnitine administration significantly improved serum alanine transaminase and aspartate transaminase levels along with a histological improvement in the NAFLD activity score, while steatosis and fibrosis were not improved. Gene expression profiling revealed a significant improvement in the inflammation and profibrotic gene signature as well as the recovery of lipid metabolism. Long-term l-carnitine administration to atherogenic plus high-fat diet MASH mice substantially improved liver histology (inflammation, steatosis, and fibrosis) and significantly reduced the incidence of liver tumors. l-carnitine directly reduced the expression of the MASH-associated and stress-induced transcriptional factor early growth response 1. Early growth response 1 activated the promoter activity of neural precursor cell expressed, developmentally downregulated protein 9 (NEDD9), an oncogenic protein. Thus, l-carnitine reduced the activation of the NEDD9, focal adhesion kinase 1, and AKT oncogenic signaling pathway.

CONCLUSIONS

Short-term l-carnitine administration ameliorated MASH through its anti-inflammatory effects. Long-term l-carnitine administration potentially improved the steatosis and fibrosis of MASH and may eventually reduce the risk of HCC.

Viral escape from NK-cell-mediated immunosurveillance: A lesson for cancer immunotherapy?

Natural killer (NK) cells are innate lymphocytes that participate in immune responses against virus-infected cells and tumors. As a countermeasure, viruses and tumors employ strategies to evade NK-cell-mediated immunosurveillance. In this review, we examine immune evasion strategies employed by viruses, focusing on examples from human CMV and severe acute respiratory syndrome coronavirus 2. We explore selected viral evasion mechanisms categorized into three classes: (1) providing ligands for the inhibitory receptor NKG2A, (2) downregulating ligands for the activating receptor NKG2D, and (3) inducing the immunosuppressive cytokine transforming growth factor (TGF)-β. For each class, we draw parallels between immune evasion by viruses and tumors, reviewing potential opportunities for overcoming evasion in cancer therapy. We suggest that in-depth investigations of host-pathogen interactions between viruses and NK cells will not only deepen our understanding of viral immune evasion but also shed light on how NK cells counter such evasion attempts. Thus, due to the parallels of immune evasion by viruses and tumors, we propose that insights gained from antiviral NK-cell responses may serve as valuable lessons that can be leveraged for designing future cancer immunotherapies.

Insights into the Transcriptome of Human Cytomegalovirus: A Comprehensive Review

Human cytomegalovirus (HCMV) is a widespread pathogen that poses significant risks to immunocompromised individuals. Its genome spans over 230 kbp and potentially encodes over 200 open-reading frames. The HCMV transcriptome consists of various types of RNAs, including messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs), with emerging insights into their biological functions. HCMV mRNAs are involved in crucial viral processes, such as viral replication, transcription, and translation regulation, as well as immune modulation and other effects on host cells. Additionally, four lncRNAs (RNA1.2, RNA2.7, RNA4.9, and RNA5.0) have been identified in HCMV, which play important roles in lytic replication like bypassing acute antiviral responses, promoting cell movement and viral spread, and maintaining HCMV latency. CircRNAs have gained attention for their important and diverse biological functions, including association with different diseases, acting as microRNA sponges, regulating parental gene expression, and serving as translation templates. Remarkably, HCMV encodes miRNAs which play critical roles in silencing human genes and other functions. This review gives an overview of human cytomegalovirus and current research on the HCMV transcriptome during lytic and latent infection.

Polyploid giant cancer cells, cytokines and cytomegalovirus in breast cancer progression

BACKGROUND

Breast cancer is the most common cancer among women. Accumulated evidence over the past decades indicates a very high prevalence of human cytomegalovirus (HCMV) in breast cancer. High-risk HCMV strains possess a direct oncogenic effect displayed by cellular stress, polyploid giant cancer cells (PGCCs) generation, stemness, and epithelial-to-mesenchymal transition (EMT) leading to cancer of aggressive phenotype. Breast cancer development and progression have been regulated by several cytokines where the latter can promote cancer cell survival, help in tumor immune evasion, and initiate the EMT process, thereby resulting in invasion, angiogenesis, and breast cancer metastasis. In the present study, we screened cytokines expression in cytomegalovirus-transformed HMECs (CTH cells) cultures infected with HCMV high-risk strains namely, HCMV-DB and BL, as well as breast cancer biopsies, and analyzed the association between cytokines production, PGCCs count, and HCMV presence in vitro and in vivo.

METHODS

In CTH cultures and breast cancer biopsies, HCMV load was quantified by real-time qPCR. PGCCs count in CTH cultures and breast cancer biopsies was identified based on cell morphology and hematoxylin and eosin staining, respectively. CTH supernatants were evaluated for the production of TGF-β, IL-6, IL1-β, and IL-10 by ELISA assays. The above-mentioned cytokines expression was assessed in breast cancer biopsies using reverse transcription-qPCR. The correlation analyses were performed using Pearson correlation test.

RESULTS

The revealed PGCCs/cytokine profile in our in vitro CTH model matched that of the breast cancer biopsies, in vivo. Pronounced cytokine expression and PGCCs count were detected in particularly CTH-DB cultures and basal-like breast cancer biopsies.

CONCLUSIONS

The analysis of cytokine profiles in PGCCs present mostly in basal-like breast cancer biopsies and derived from CTH cells chronically infected with the high-risk HCMV strains might have the potential to provide novel therapies such as cytokine-based immunotherapy which is a promising field in cancer treatments.

Critical Role for the Human Cytomegalovirus Major Immediate Early Proteins in Recruitment of RNA Polymerase II and H3K27Ac To an Enhancer-Like Element in OriLyt

Human cytomegalovirus (HCMV) is an opportunistic pathogen that infects most of the population. The complex 236 kbp genome encodes more than 170 open reading frames, whose expression is temporally regulated by both viral transcriptional regulators and cellular factors that control chromatin and transcription. Here, we have used state of the art genomic technologies to investigate the viral transcriptome in conjunction with 2 key transcriptional regulators: Pol II and H3K27Ac. Although it is well known that the major immediate early (IE) proteins activate early gene expression through both direct and indirect interactions, and that histone modifications play an important role in regulating viral gene expression, the role of the IE proteins in modulating viral chromatin is not fully understood. To address this question, we have used a virus engineered for conditional expression of the IE proteins combined with RNA and Chromatin immunoprecipitation (ChIP) analyses to assess the role of these proteins in modulating both viral chromatin and gene expression. Our results show that (i) there is an enhancer-like element in OriLyt that is extraordinarily enriched in H3K27Ac; (ii) in addition to activation of viral gene expression, the IE proteins play a critical role in recruitment of Pol II and H3K27Ac to this element. IMPORTANCE HCMV is an important human pathogen associated with complications in transplant patients and birth defects. The complex program of viral gene expression is regulated by both viral proteins and host factors. Here, we have investigated the role of the immediate early proteins in regulating the viral epigenome. Our results show that the viral immediate early proteins bring about an enormous enrichment of H3K27Ac marks at the OriLyt RNA4.9 promoter, concomitant with an increase in RNA4.9 expression. This epigenetic characteristic adds importantly to the view that OriLyt has structural and functional characteristics of a strong enhancer that, we now discover, is regulated by IE proteins.

Human cytomegalovirus blocks canonical TGFβ signaling during lytic infection to limit induction of type I interferons

Human cytomegalovirus (HCMV) microRNAs (miRNAs) significantly rewire host signaling pathways to support the viral lifecycle and regulate host cell responses. Here we show that SMAD3 expression is regulated by HCMV miR-UL22A and contributes to the IRF7-mediated induction of type I IFNs and IFN-stimulated genes (ISGs) in human fibroblasts. Addition of exogenous TGFβ interferes with the replication of a miR-UL22A mutant virus in a SMAD3-dependent manner in wild type fibroblasts, but not in cells lacking IRF7, indicating that downregulation of SMAD3 expression to limit IFN induction is important for efficient lytic replication. These findings uncover a novel interplay between SMAD3 and innate immunity during HCMV infection and highlight the role of viral miRNAs in modulating these responses.

Viral Manipulation of the Host Epigenome as a Driver of Virus-Induced Oncogenesis

Tumorigenesis due to viral infection accounts for a high fraction of the total global cancer burden (15–20%) of all human cancers. A comprehensive understanding of the mechanisms by which viral infection leads to tumor development is extremely important. One of the main mechanisms by which viruses induce host cell proliferation programs is through controlling the host’s epigenetic machinery. In this review, we dissect the epigenetic pathways through which oncogenic viruses can integrate their genome into host cell chromosomes and lead to tumor progression. In addition, we highlight the potential use of drugs based on histone modifiers in reducing the global impact of cancer development due to viral infection.

Epigenetic reprogramming of host and viral genes by Human Cytomegalovirus infection in Kasumi-3 myeloid progenitor cells at early times post-infection

HCMV establishes latency in myeloid cells. Using the Kasumi-3 latency model, we previously showed that lytic gene expression is activated prior to establishment of latency in these cells. The early events in infection may have a critical role in shaping establishment of latency. Here, we have used an integrative multi-omics approach to investigate dynamic changes in host and HCMV gene expression and epigenomes at early times post infection. Our results show dynamic changes in viral gene expression and viral chromatin. Analyses of Pol II, H3K27Ac and H3K27me3 occupancy of the viral genome showed that 1) Pol II occupancy was highest at the MIEP at 4 hours post infection. However, it was observed throughout the genome; 2) At 24 hours, H3K27Ac was localized to the major immediate early promoter/enhancer and to a possible second enhancer in the origin of replication OriLyt; 3) viral chromatin was broadly accessible at 24 hpi. In addition, although HCMV infection activated expression of some host genes, we observed an overall loss of de novo transcription. This was associated with loss of promoter-proximal Pol II and H3K27Ac, but not with changes in chromatin accessibility or a switch in modification of H3K27.Importance.HCMV is an important human pathogen in immunocompromised hosts and developing fetuses. Current anti-viral therapies are limited by toxicity and emergence of resistant strains. Our studies highlight emerging concepts that challenge current paradigms of regulation of HCMV gene expression in myeloid cells. In addition, our studies show that HCMV has a profound effect on de novo transcription and the cellular epigenome. These results may have implications for mechanisms of viral pathogenesis.

Truncated YY1 interacts with BASP1 through a 339KLK341 motif in YY1 and suppresses vascular smooth muscle cell growth and intimal hyperplasia after vascular injury

AIMS

In-stent restenosis and late stent thrombosis are complications associated with the use of metallic and drug-coated stents. Strategies that inhibit vascular smooth muscle cell (SMC) proliferation without affecting endothelial cell (EC) growth would be helpful in reducing complications arising from percutaneous interventions. Our group previously showed that the forced expression of the injury-inducible zinc finger (ZNF) transcription factor, yin yang-1 (YY1) comprising 414 residues inhibits neointima formation in carotid arteries of rabbits and rats. YY1 inhibits SMC proliferation without affecting EC growth. Identifying a shorter version of YY1 retaining cell-selective inhibition would make it more amenable for potential use as a gene therapeutic agent.

METHODS AND RESULTS

We dissected YY1 into a range of shorter fragments (YY1A-D, YY1Δ) and found that the first two ZNFs in YY1 (construct YY1B, spanning 52 residues) repressed SMC proliferation. Receptor Binding Domain analysis predicts a three residue (339KLK341) interaction domain. Mutation of 339KLK341 to 339AAA341 in YY1B (called YY1Bm) abrogated YY1B's ability to inhibit SMC but not EC proliferation and migration. Incubation of recombinant GST-YY1B and GST-YY1Bm with SMC lysates followed by precipitation with glutathione-agarose beads and mass spectrometric analysis identified a novel interaction between YY1B and BASP1. Overexpression of BASP1, like YY1, inhibited SMC but not EC proliferation and migration. BASP1 siRNA partially rescued SMC from growth inhibition by YY1B. In the rat carotid balloon injury model, adenoviral overexpression of YY1B, like full-length YY1, reduced neointima formation, whereas YY1Bm had no such effect. CD31 immunostaining suggested YY1B could increase re-endothelialization in a 339KLK341-dependent manner.

CONCLUSIONS

These studies identify a truncated form of YY1 (YY1B) that can interact with BASP1 and inhibits SMC proliferation, migration and intimal hyperplasia after balloon injury of rat carotid arteries as effectively as full length YY1. We demonstrate the therapeutic potential of YY1B in vascular proliferative disease.

Human Cytomegalovirus miRNAs Regulate TGF-β to Mediate Myelosuppression while Maintaining Viral Latency in CD34+ Hematopoietic Progenitor Cells

Infection with human cytomegalovirus (HCMV) remains a significant cause of morbidity and mortality following hematopoietic stem cell transplant (HSCT) because of various hematologic problems, including myelosuppression. Here, we demonstrate that latently expressed HCMV miR-US5-2 downregulates the transcriptional repressor NGFI-A binding protein (NAB1) to induce myelosuppression of uninfected CD34⁺ hematopoietic progenitor cells (HPCs) through an increase in TGF-β production. Infection of HPCs with an HCMVΔmiR-US5-2 mutant resulted in decreased TGF-β expression and restoration of myelopoiesis. In contrast, we show that infected HPCs are refractory to TGF-β signaling as another HCMV miRNA, miR-UL22A, downregulates SMAD3, which is required for maintenance of latency. Our data suggest that latently expressed viral miRNAs manipulate stem cell homeostasis by inducing secretion of TGF-β while protecting infected HPCs from TGF-β-mediated effects on viral latency and reactivation. These observations provide a mechanism through which HCMV induces global myelosuppression following HSCT while maintaining lifelong infection in myeloid lineage cells.

Subversion of Immune Response by Human Cytomegalovirus

Human cytomegalovirus (HCMV) is the most common cause of congenital infections and is an important pathogen in immunocompromised individuals. Despite a robust host immune system, HCMV able to replicate, evade host defenses, establish latency for life. A significant portion of HCMV genome dedicated to encode gene products for modulation of host immune response. Growing number of HCMV gene products are being recognized to play role in immune evasion. Information on viral immune evasion mechanisms by which HCMV persists in host will be useful in devising antiviral intervention strategies and development of new vaccines. This minireview provides a brief overview of immune evasion strategy adapted by HCMV by utilizing its gene products in modulation of host immune response.

A high level of urinary retinol-binding protein is associated with cytomegalovirus infection in kidney transplantation

The indirect effects of cytomegalovirus (CMV) viremia can be related to chronic changes in renal allograft structure, but its real impact in early and late graft function remains speculative. A total of 159 patients undergoing renal transplantation using a preemptive therapeutic strategy to prevent CMV disease were included in the present study. The patients were prospectively followed, with serial measurements of urinary retinol-binding protein (uRBP), a marker of proximal tubule injury. uRBP levels and their dynamic performance were compared according to CMV viremia and the 5-year estimated glomerular filtration rate (eGFR), as measured with the modification of diet in renal disease (MDRD) equation. CMV viremia was detected in 79.9% of the patients, with high uRBP levels being detected in 76.0% of these patients (compared with 40.7% in CMV-, P=0.005). High uRBP was associated with male recipients (P=0.02), the number of mismatches (P=0.02) and CMV infection (P=0.001). Five-year eGFR was worse in patients with high uRBP levels (50.3 ± 25.8 compared with 59.8 ± 26.4 ml/min, P=0.04). In a multivariate model, eGFR <60 ml/min was associated with donor age (P<0.001), the number of mismatches (P=0.04), thymoglobulin dose (P=0.02), the presence of and time with delayed graft function (DGF) (P=0.005 and P=0.04), 1-month tacrolimus levels (P=0.03), and uRBP levels after CMV treatment (P=0.01). Patients with CMV viremia in whom uRBP levels were normalized up to 3 months after treatment showed significantly better 5-year eGFR than those in whom uRBP remained high: 61.0 ± 24.2 compared with 42.3 ± 23.9 ml/min, P<0.001. CMV viremia was associated with high uRBP levels, which represent a profile of proximal tubule injury, and the dynamic performance of uRBP after treatment was associated with long-term kidney graft function.

The Human Cytomegalovirus, from Oncomodulation to Oncogenesis

Besides its well-described impact in immunosuppressed patients, the role of human cytomegalovirus (HCMV) in the pathogenesis of cancer has been more recently investigated. In cancer, HCMV could favor the progression and the spread of the tumor, a paradigm named oncomodulation. Although oncomodulation could account for part of the protumoral effect of HCMV, it might not explain the whole impact of HCMV infection on the tumor and the tumoral microenvironment. On the contrary cases have been reported where HCMV infection slows down the progression and the spread of the tumor. In addition, HCMV proteins have oncogenic properties per se, HCMV activates pro-oncogenic pathways in infected cells, and recently the direct transformation of cells following HCMV infection has been described, which gave rise to tumors when injected in mice. Thus, beyond the oncomodulation model, this review will assess the direct transforming role of HMCV-infected cells and the potential classification of HCMV as an oncovirus.

Human cytomegalovirus immediate-early protein promotes survival of glioma cells through interacting and acetylating ATF5

Human cytomegalovirus (HCMV), a widespread beta-herpes virus, infects a high percentage of gliomas. HCMV is specifically detected in human gliomas at a low level of expression raises the possibility that it may regulate the malignant phenotype in a chronic manner. Although HCMV is not recognized as an oncogenic virus, it might dysregulate signaling pathways involved in initiation and promotion of malignancy.Here, our immunohistochemical staining reveals that nucleus staining of the HCMV 86-kDa immediate-early protein (IE86) is markedly increased in GBM (58.56%) compared with that in nontumorous samples (4.20%) and low-grade glioma(19.56%). IE86 staining positively correlates with the staining of activating transcription factor 5 (ATF5) which is essential for glioma cell viability and proliferation suggesting that HCMV IE86 could have important implications in glioma biology. Moreover, we find that the IE86 overexpression enhances glioma cell's growth in vitro and in vivo. We demonstrate that IE86 protein physically interacts with, and acetylates ATF5 thereby promoting glioma cell survival. Therefore, our findings illustrate the biological significance of HCMV infection in accelerating glioma progression, and provide novel evidence that HCMV infection may serve as a therapeutic target in human glioma.

TGF-β1 expression in regulatory NK1.1-CD4+NKG2D+ T cells dependents on the PI3K-p85α/JNK, NF-κB and STAT3 pathways

NK1.1^-CD4⁺NKG2D⁺ cells exert their immune-regulatory function in tumor as an unconventional regulatory T cell subset through the production of TGF-β1; however, the molecular mechanisms involving with the activation of nuclear factors for TGF-β1 transcription remain unclear. Here we determined that the PI3K-p85α subunit was specifically activated in NK1.1^-CD4⁺NKG2D⁺ cells following an 8-hour stimulation by sRAE-1 or α-CD3/sRAE-1, subsequently leading to the activation of PI3K-p110, Akt, and JNK. On the contrary, α-CD3/α-CD28 stimulation did not induce the activation of PI3K-p85 and JNK. Consequently, activation of the nuclear transcription factor AP-1 as a consequence of JNK activation regulated TGF-β1 expression in NK1.1^-CD4⁺NKG2D⁺ cells. Furthermore, activation of NF-κB in NK1.1^-CD4⁺NKG2D⁺ cells resulted from both protein kinase C activation downstream of TCR/CD3 signaling and PI3K activation induced by NKG2D engagement. The STAT3-Y705 phosphorylation, as activated by PI3K, under stimulations of the sRAE-1 or α-CD3/sRAE-1 also contributed to the TGF-β1 expression in NK1.1^-CD4⁺NKG2D⁺ cells. Moreover, ChIP assay confirmed that STAT3 was capable of binding with the promoter regions of TGF-β1. In conclusion, our data showed that the TGF-β1 transcription in NK1.1^-CD4⁺NKG2D⁺ cells induced by sRAE-1 or α-CD3/sRAE-1 was involved with the AP-1, NF-κB, and STAT3 signaling pathways; therefore, regulation of AP-1, NF-κB, and STAT3 activation may play important roles in the development and function of NK1.1^-CD4⁺NKG2D⁺ cells.

Viruses as key modulators of the TGF-β pathway; a double-edged sword involved in cancer

Transforming growth factor-β (TGF-β) signaling pathway is a key network in cell signaling that controls vital processes such as proliferation, differentiation, apoptosis, epithelial-mesenchymal transition, and migration, thus acting as a double-edged sword in normal development and diseases, in particular organ fibrosis, vascular disorders, and cancer. Early in tumorigenesis, the pathway exerts anti-tumor effects through suppressing cell cycle and inducing apoptosis, while during late stages, it functions as a tumor promoter by enhancing tumor invasiveness and metastasis. This signaling pathway can be perturbed by environmental and genetic factors such as microbial interference and mutation, respectively. In this way, the present review describes the modulation of the TGF-β pathway by oncogenic human viral pathogens and other viruses. The main mechanisms by which viruses interferes with TGF-β signaling seems to be through (1) the alteration of either TGF-β protein expression or activation, (2) the modulation of the TGF-β receptors or SMADs factors (by interfering with their levels and functions), (3) the alteration of none-SMAD pathways, and (4) indirect interaction with the pathway by the modulation of transcriptional co-activator/repressor and regulators of the pathway. Given the axial role of this pathway in tumorigenesis, it can be regarded as an attractive target for cancer therapy. Hence, further investigations on this subject may represent molecular targets among either TGF-β signaling molecules or viral factors for the treatment and management of viral infection consequences such as cancer.

Characterization of a thienylcarboxamide derivative that inhibits the transactivation functions of cytomegalovirus IE2 and varicella zoster virus IE62

Previously we established reporter cell lines for human cytomegalovirus (HCMV) and varicella zoster virus (VZV) and identified several antiviral compounds against these viruses using the reporter cells. In this study, we found that one of the identified anti-HCMV compounds, a thienylcarboxamide derivative (coded as 133G4), was effective against not only HCMV but also VZV. The following findings indicate that 133G4 inhibits the activation of early gene promoters by HCMV IE2 and VZV IE62: i) 133G4 decreased the expression of HCMV early and late genes but not that of HCMV IE1/IE2 in HCMV-infected cells, ii) 133G4 inhibited the activation of several HCMV early gene promoters of transiently-transfected plasmids in HCMV-infected cells, and iii) in transient transfection assays, 133G4 decreased the activation of HCMV (or VZV) early gene promoters by HCMV IE2 (or VZV IE62) in the absence of other viral protein expression. The inhibition of early gene activation was observed in the human and African green monkey cell lines but not in the rodent cell lines, and the compound was not effective against murine CMV. In addition, VZV IE62 activated HCMV early promoters, and 133G4 still inhibited such promoter activation. Therefore, we hypothesized that 133G4 targets a cellular factor used commonly in activation of human herpesvirus promoters and examined whether 133G4 affects the functions of cellular proteins USF1, TBP, Med25 and EAP, the involvement of which in VZV IE62-dependent viral gene activation has been well characterized. Our experimental results using one-hybrid and bimolecular fluorescence complementation assays demonstrated that 133G4 did not inhibit the recruitment of USF1 or TBP to their binding sites, nor inhibited the direct interactions of VZV IE62 with Med25 and EAP. Thus, 133G4 is a unique anti-VZV and -HCMV compound, which warrants further studies to find out its inhibitory mechanism.

Association between human cytomegalovirus infection and histone acetylation level in various histological types of glioma

At present, glioma is the most common intracranial tumor and accounts for 40–60% of intracranial tumors. Glioma is highly anaplastic and demonstrates invasive growth. Although considerable progression has been achieved in the treatment of malignant glioma, the prognosis of this disease remains poor. Over the previous decade, several studies have confirmed that human cytomegalovirus (HCMV) enhances the growth or survival of tumors. This is likely to occur through mechanisms distinct from those of classic tumor viruses, which express transforming viral oncoproteins in the majority of tumor cells. The immediate-early 2 protein (IE86; 86 kDa) of HCMV is a key regulator for viral replication and host cell proliferation. The present study aimed to identify the association between the acetylation level and HCMV IE86 expression in various histological types of glioma. Tissue samples were obtained from 60 patients with glioma, consisting of 25 patients with glioblastoma multiforme (GBM), 16 patients with anaplastic glioma and 19 patients with low-grade glioma, in addition to 9 tissue samples obtained from the normal cortex, which were used as the control. The in situ protein expression of IE86, which is encoded by the IE2 gene, activating transcription factor 5 (ATF5), P300, acetyl-histone H3K9 and acetyl-histone H3K14 was detected by immunohistochemistry. The mRNA levels of ATF5, IE2 and P300 were measured by reverse transcription-quantitative polymerase chain reaction in GBM, anaplastic glioma, low-grade glioma and normal cortex tissue specimens. The protein levels of ATF5, IE86, P300, acetyl-histone H3K9 and acetyl-histone H3K14 were assessed by western blot analysis in high-grade glioma, low-grade glioma and normal cortex tissues. Analysis of the expression of the proteins revealed that the excessive expression of the HCMV IE86 protein is associated with the malignancy degree and acetylation level in glioma. IE86 expression is also associated with ATF5, which is an anti-apoptotic protein that is highly expressed in malignant glioma, but not in normal brain tissues. The expression level of IE86 may demonstrate considerable importance for the evaluation of the malignancy degree of human gliomas and extensive application in diagnostic and therapeutic medicine.

Cytomegalovirus and glioma: putting the cart before the horse

In 1908, Oluf Bang and Vilhelm Ellerman laid the foundation for theory of oncoviruses by demonstrating that the avian erythroblastosis (a form of chicken leukaemia) could be transmitted by cell-free extracts. Since then, it has been shown very convincingly that viruses can directly cause several human cancers by various mechanisms. Epidemiological data imply that viruses are the second most important risk factor for cancer development in humans, exceeded only by tobacco consumption. Although the ability of certain viruses (hepatitis B and C, human papillomavirus, etc) to cause cancer has been time tested and proven scientifically, there are several other potential viral candidates whose role in oncogenesis is more controversial. One such controversial scenario involves the role of cytomegalovirus (CMV) in malignant gliomas, the most common form of primary brain tumour. CMV first attracted attention about a decade ago when CMV gene products were found in glioma tissue but not in normal brain. Since this initial observation, several different groups have shown an oncomodulatory effect of CMV; however, direct association between CMV infection and incidence of glioma is lacking. In this review, we will evaluate the evidence, both preclinical and clinical, regarding the possible role of CMV in gliomagenesis and maintenance. We will also critically evaluate the rationale for using antiviral drugs in the treatment of patients with glioma.

Cytomegalovirus enhances macrophage TLR expression and MyD88-mediated signal transduction to potentiate inducible inflammatory responses

Circulating monocytes carrying human CMV (HCMV) migrate into tissues, where they differentiate into HCMV-infected resident macrophages that upon interaction with bacterial products may potentiate tissue inflammation. In this study, we investigated the mechanism by which HCMV promotes macrophage-orchestrated inflammation using a clinical isolate of HCMV (TR) and macrophages derived from primary human monocytes. HCMV infection of the macrophages, which was associated with viral DNA replication, significantly enhanced TNF-α, IL-6, and IL-8 gene expression and protein production in response to TLR4 ligand (LPS) stimulation compared with mock-infected LPS-stimulated macrophages during a 6-d in vitro infection. HCMV infection also potentiated TLR5 ligand-stimulated cytokine production. To elucidate the mechanism by which HCMV infection potentiated inducible macrophage responses, we show that infection by HCMV promoted the maintenance of surface CD14 and TLR4 and TLR5, which declined over time in mock-infected macrophages, and enhanced both the intracellular expression of adaptor protein MyD88 and the inducible phosphorylation of IκBα and NF-κB. These findings provide additional information toward elucidating the mechanism by which HCMV potentiates bacteria-induced NF-κB-mediated macrophage inflammatory responses, thereby enhancing organ inflammation in HCMV-infected tissues.

Activation of TGF-β1 promoter by hepatitis C virus-induced AP-1 and Sp1: role of TGF-β1 in hepatic stellate cell activation and invasion

Our previous studies have shown the induction and maturation of transforming growth factor-beta 1 (TGF-β1) in HCV-infected human hepatoma cells. In this study, we have investigated the molecular mechanism of TGF-β1 gene expression in response to HCV infection. We demonstrate that HCV-induced transcription factors AP-1, Sp1, NF-κB and STAT-3 are involved in TGF-β1 gene expression. Using chromatin immunoprecipitation (ChIP) assay, we further show that AP-1 and Sp1 interact with TGF-b1 promoter in vivo in HCV-infected cells. In addition, we demonstrate that HCV-induced TGF-β1 gene expression is mediated by the activation of cellular kinases such as p38 MAPK, Src, JNK, and MEK1/2. Next, we determined the role of secreted bioactive TGF-β1 in human hepatic stellate cells (HSCs) activation and invasion. Using siRNA approach, we show that HCV-induced bioactive TGF-β1 is critical for the induction of alpha smooth muscle actin (α-SMA) and type 1 collagen, the markers of HSCs activation and proliferation. We further demonstrate the potential role of HCV-induced bioactive TGF-β1 in HSCs invasion/cell migration using a transwell Boyden chamber. Our results also suggest the role of HCV-induced TGF-β1 in HCV replication and release. Collectively, these observations provide insight into the mechanism of TGF-β1 promoter activation, as well as HSCs activation and invasion, which likely manifests in liver fibrosis associated with HCV infection.

Inhibition of p53 transcriptional activity by human cytomegalovirus UL44

Human cytomegalovirus (HCMV) stimulates cellular synthesis of DNA and proteins and induces transition of the cell cycle from G(1) to S and G(2) /M phase, in spite of increased amounts of p53 in the infected cells. The immediate early protein IE2-86  kDa (IE86) tethers a transcriptional repression domain to p53; however, its repression of p53 function is not enough to abrogate the G(1) checkpoint function of p53. Other HCMV proteins that suppress the activity of p53 were investigated in this study. Of the HCMV proteins that bind to p53 when assessed by immunoprecipitation and immunoblot analysis, HCMV UL44 was chosen as a candidate protein. It was found that reporter gene containing p53 consensus sequence was activated by transfection with wild type p53, but when plasmids of p53 with IE86 or UL44 were co-transfected, p53 transcriptional activity was decreased to 3-7% of the p53 control in a dose-dependent manner. When the deletion mutant of UL44 was co-transected with p53, the carboxyl one-third portion of UL44 had little effect on inhibition of p53 transcriptional activity. The amount of mRNA p21 was measured in H1299 by real time PCR after transfection of the combination of p53 and UL44 vectors and it was found that p21 transcription by p53 was inhibited dose-dependently by UL44. Increased G0/G1 and decreased S phases in p53 wild type-transfected H1299 cells were recovered to the level of p53 mutant type-transfected ones by the additional transfection of UL44 in a dose-dependent manner. In conclusion, the transcriptional activity of p53 is suppressed by UL44 as well as by IE86.

Consensus on the role of human cytomegalovirus in glioblastoma

The human cytomegalovirus (HCMV) and glioma symposium was convened on April 17, 2011 in Washington, DC, and was attended by oncologists and virologists involved in studying the relationship between HCMV and gliomas. The purpose of the meeting was to reach a consensus on the role of HCMV in the pathology of gliomas and to clarify directions for future research. First, the group summarized data that describe how HCMV biology overlaps with the key pathways of cancer. Then, on the basis of published data and ongoing research, a consensus was reached that there is sufficient evidence to conclude that HCMV sequences and viral gene expression exist in most, if not all, malignant gliomas, that HCMV could modulate the malignant phenotype in glioblastomas by interacting with key signaling pathways; and that HCMV could serve as a novel target for a variety of therapeutic strategies. In summary, existing evidence supports an oncomodulatory role for HCMV in malignant gliomas, but future studies need to focus on determining the role of HCMV as a glioma-initiating event.

Cytomegalovirus and tumors: two players for one goal-immune escape

Cytomegalovirus (CMV) and the human tumor cell share the same objectives: escape the recognition and destruction by the immune system and establish a state of immune tolerance conducive for their development. For early tumor development, the escape of the first lines of defense of the immune surveillance is a critical step which determines survival or destruction. The presence of CMV on the tumor site and its involvement in carcinogenesis as initiator or promoter is increasingly documented. In this article, we highlight the similarity between mechanisms used by tumors and CMV to circumvent the immune defenses and evade from immune surveillance. We suggest that CMV and tumors help one another for their common objective. CMV gets shelter in immunologically poor environment of the tumor cells. In return CMV, by acting directly on the cancer cell and/or on the tumor microenvironment, provides the tumor cell the ways to promote its immune escape and development of immune tolerance.

Glioma-associated cytomegalovirus mediates subversion of the monocyte lineage to a tumor propagating phenotype

PURPOSE

Cytomegalovirus (CMV) has been ubiquitously detected within high-grade gliomas, but its role in gliomagenesis has not been fully elicited.

EXPERIMENTAL DESIGN

Glioblastoma multiforme (GBM) tumors were analyzed by flow cytometry to determine CMV antigen expression within various glioma-associated immune populations. The glioma cancer stem cell (gCSC) CMV interleukin (IL)-10 production was determined by ELISA. Human monocytes were stimulated with recombinant CMV IL-10 and levels of expression of p-STAT3, VEGF (vascular endothelial growth factor), TGF-β, viral IE1, and pp65 were determined by flow cytometry. The influence of CMV IL-10-treated monocytes on gCSC biology was ascertained by functional assays.

RESULTS

CMV showed a tropism for macrophages (MΦ)/microglia and CD133+ gCSCs within GBMs. The gCSCs produce CMV IL-10, which induces human monocytes (the precursor to the central nervous system MΦs/microglia) to assume an M2 immunosuppressive phenotype (as manifested by downmodulation of the major histocompatibility complex and costimulatory molecules) while upregulating immunoinhibitory B7-H1. CMV IL-10 also induces expression of viral IE1, a modulator of viral replication and transcription in the monocytes. Finally, the CMV IL-10-treated monocytes produced angiogenic VEGF, immunosuppressive TGF-β, and enhanced migration of gCSCs.

CONCLUSIONS

CMV triggers a feedforward mechanism of gliomagenesis by inducing tumor-supportive monocytes.

Human cytomegalovirus induces TGF-β1 activation in renal tubular epithelial cells after epithelial-to-mesenchymal transition

Human cytomegalovirus (HCMV) infection is associated epidemiologically with poor outcome of renal allografts due to mechanisms which remain largely undefined. Transforming growth factor-β1 (TGF-β1), a potent fibrogenic cytokine, is more abundant in rejecting renal allografts that are infected with either HCMV or rat CMV as compared to uninfected, rejecting grafts. TGF-β1 induces renal fibrosis via epithelial-to-mesenchymal transition (EMT) of renal epithelial cells, a process by which epithelial cells acquire mesenchymal characteristics and a migratory phenotype, and secrete molecules associated with extracellular matrix deposition and remodeling. We report that human renal tubular epithelial cells infected in vitro with HCMV and exposed to TGF-β1 underwent morphologic and transcriptional changes of EMT, similar to uninfected cells. HCMV infected cells after EMT also activated extracellular latent TGF-β1 via induction of MMP-2. Renal epithelial cells transiently transfected with only the HCMV IE1 or IE2 open reading frames and stimulated to undergo EMT also induced TGF-β1 activation associated with MMP-2 production, suggesting a role for these viral gene products in MMP-2 production. Consistent with the function of these immediate early gene products, the antiviral agents ganciclovir and foscarnet did not inhibit TGF-β1 production after EMT by HCMV infected cells. These results indicate that HCMV infected renal tubular epithelial cells can undergo EMT after exposure to TGF-β1, similar to uninfected renal epithelial cells, but that HCMV infection by inducing active TGF-β1 may potentiate renal fibrosis. Our findings provide in vitro evidence for a pathogenic mechanism that could explain the clinical association between HCMV infection, TGF-β1, and adverse renal allograft outcome.

Human cytomegalovirus (HCMV) is a common virus that establishes lifelong persistence in the host. Although asymptomatic in healthy people, HCMV can reactivate and cause disease in immunosuppressed patients, such as those undergoing kidney transplantation. HCMV infection is associated with inferior renal allograft survival compared to transplants without HCMV infection. HCMV infected allografts also contain higher levels of the fibrogenic cytokine, transforming growth factor-β1 (TGF-β1), compared to uninfected allografts. TGF-β1 is a potent inducer of renal fibrosis and causes epithelial-to-mesenchymal transition (EMT), whereby epithelial cells acquire characteristics of cells of mesenchymal origin and express molecules associated with fibrosis. Our work shows that renal epithelial cells infected in vitro with HCMV can undergo EMT, but that HCMV infected cells produce greater amounts of the fibrogenic molecule TGF-β1, compared to uninfected cells after EMT. We have shown that this effect is likely due to specific HCMV genes (IE1, IE2), and cannot be prevented by administration of antivirals such as ganciclovir or foscarnet. These data suggest that HCMV may contribute to adverse renal allograft outcome by exacerbating TGF-β1 induced renal fibrosis. Understanding such mechanisms will permit the development of treatments that could improve long-term renal allograft survival in HCMV infected patients.

Role of noncovalent SUMO binding by the human cytomegalovirus IE2 transactivator in lytic growth

The 86-kDa immediate-early 2 (IE2) protein of human cytomegalovirus (HCMV) is a promiscuous transactivator essential for viral gene expression. IE2 is covalently modified by SUMO at two lysine residues (K175 and K180) and also interacts noncovalently with SUMO. Although SUMOylation of IE2 has been shown to enhance its transactivation activity, the role of SUMO binding is not clear. Here we showed that SUMO binding by IE2 is necessary for its efficient transactivation function and for viral growth. IE2 bound physically to SUMO-1 through a SUMO-interacting motif (SIM). Mutations in SIM (mSIM) or in both SUMOylation sites and SIM (KR/mSIM), significantly reduced IE2 transactivation effects on viral early promoters. The replication of IE2 SIM mutant viruses (mSIM or KR/mSIM) was severely depressed in normal human fibroblasts. Analysis of viral growth curves revealed that the replication defect of the mSIM virus correlated with low-level accumulation of SUMO-modified IE2 and of viral early and late proteins. Importantly, both the formation of viral transcription domains and the association of IE2 with viral promoters in infected cells were significantly reduced in IE2 SIM mutant virus infection. Furthermore, IE2 was found to interact with the SUMO-modified form of TATA-binding protein (TBP)-associated factor 12 (TAF12), a component of the TFIID complex, in a SIM-dependent manner, and this interaction enhanced the transactivation activity of IE2. Our data demonstrate that the interaction of IE2 with SUMO-modified proteins plays an important role for the progression of the HCMV lytic cycle, and they suggest a novel viral mechanism utilizing the cellular SUMO system.

Human cytomegalovirus IE2 86 and IE2 40 proteins differentially regulate UL84 protein expression posttranscriptionally in the absence of other viral gene products

It has previously been demonstrated that, during human cytomegalovirus infection, the viral IE2 86 and IE2 40 proteins are both important for the expression of an early-late viral protein, UL84. Here, we show that expression of the UL84 protein is enhanced upon cotransfection with either IE2 86 or IE2 40, although IE2 40 appears to play a more important role. The UL84 protein levels are tightly linked to the amount of IE2 40 present, but this does not appear to be true for IE2 86. RNA remains constant for all corresponding proteins, indicating posttranscriptional regulation of UL84. The first 105 amino acids of UL84 are necessary and sufficient for this phenotype, and this region is also required for an interaction with IE2 86 and IE2 40. Treatment with proteasome inhibitors shows that UL84 exhibits some proteasome-dependent degradation, and UL84 is not protected against this degradation when coexpressed with IE2 86 or IE2 40. UL84 also exhibits an inhibitory effect on IE2 86 and IE2 40 protein levels in these cotransfection assays. Further, we show that the amino acid sequence of UL84 is important for the enhancement governed by IE2 40. These results indicate that IE2 86, IE2 40, and UL84 serve to regulate protein expression in a posttranscriptional fashion and that this regulation is independent of other viral proteins.

Human cytomegalovirus IE1-72 protein interacts with p53 and inhibits p53-dependent transactivation by a mechanism different from that of IE2-86 protein

Infection of host cells with human cytomegalovirus (HCMV) induces cell cycle dysregulation. Two HCMV immediate-early (IE) proteins, IE1-72 and IE2-86, are promiscuous transactivators that have been implicated in the dysregulatory events. Cellular p53 protein is accumulated to high levels in HCMV-infected cells, but the indicative marker of p53 transcriptional activity, p21, is markedly decreased. Both IE1-72 and IE2-86 were able to transactivate the p53 promoter and interact with p53 protein in DNA-transfected or HCMV-infected cells. HCMV UL84, a multiregulatory protein expressed in early periods of HCMV infection, also interacted with p53. HCMV IE1-72 prevented or disrupted p53 binding to p53-specific DNA sequences, while IE2-86 and/or UL84 enhanced p53 binding and induced supershift of this DNA-protein complex. Both HCMV IE1-72 and IE2-86 were able to inhibit p53-dependent transcriptional activation in plasmid-transfected cells. IE1-72, rather than IE2-86, was found to be responsible for p21 downregulation in HCMV-infected HEL cells. DNA transfection analysis using IE1-72 mutants revealed that exon 2/3 and the zinc finger region of IE1-72 are essential for IE1-72's effect on the repression of p53-dependent transcriptional activation. These data suggest that HCMV IE1-72 and/or IE2-86 transactivates the p53 promoter and induces p53 accumulation, but HCMV IE1-72 represses the p53 transactivation activity by a unique binding hindrance mechanism different from that of IE2-86. Thus, various modes of viral IE proteins and p53 interactions might result in multiple outcomes, such as stimulation of cellular DNA synthesis, cell cycle progression and cell cycle arrest, and prevention of program cell death.

The story of human cytomegalovirus and cancer: increasing evidence and open questions

Although human cytomegalovirus (HCMV) is generally not regarded to be an oncogenic virus, HCMV infection has been implicated in malignant diseases from different cancer entities. On the basis of our experimental findings, we developed the concept of "oncomodulation" to better explain the role of HCMV in cancer. Oncomodulation means that HCMV infects tumor cells and increases their malignancy. By this concept, HCMV was proposed to be a therapeutic target in a fraction of cancer patients. However, the clinical relevance of HCMV-induced oncomodulation remains to be clarified. One central question that has to be definitively answered is if HCMV establishes persistent virus replication in tumor cells or not. In our eyes, recent clinical findings from different groups in glioblastoma patients and especially the detection of a correlation between the numbers of HCMV-infected glioblastoma cells and tumor stage (malignancy) strongly increase the evidence that HCMV may exert oncomodulatory effects. Here, we summarize the currently available knowledge about the molecular mechanisms that may contribute to oncomodulation by HCMV as well as the clinical findings that suggest that a fraction of tumors from different entities is indeed infected with HCMV.

Transcriptional and translational regulation of TGF-beta production in response to apoptotic cells

Interaction between apoptotic cells and phagocytes through phosphatidylserine recognition structures results in the production of TGF-beta, which has been shown to play pivotal roles in the anti-inflammatory and anti-immunogenic responses to apoptotic cell clearance. Using 3T3-TbetaRII and RAWTbetaRII cells in which a truncated dominant-negative TGF-beta receptor II was stably transfected to avoid autofeedback induction of TGF-beta, we investigate the mechanisms by which TGF-beta was produced through PSRS engagement. We show, in the present study, that TGF-beta was regulated at both transcriptional and translational steps. P38 MAPK, ERK, and JNK were involved in TGF-beta transcription, whereas translation required activation of Rho GTPase, PI3K, Akt, and mammalian target of rapamycin with subsequent phosphorylation of translation initiation factor eukaryotic initiation factor 4E. Strikingly, these induction pathways for TGF-beta production were different from those initiated in the same cells responding to LPS or PMA.

Development of cell lines that provide tightly controlled temporal translation of the human cytomegalovirus IE2 proteins for complementation and functional analyses of growth-impaired and nonviable IE2 mutant viruses

The human cytomegalovirus (HCMV) IE2 86 protein is essential for viral replication. Two other proteins, IE2 60 and IE2 40, which arise from the C-terminal half of IE2 86, are important for later stages of the infection. Functional analyses of IE2 86 in the context of the infection have utilized bacterial artificial chromosomes as vectors to generate mutant viruses. One limitation is that many mutations result in debilitated or nonviable viruses. Here, we describe a novel system that allows tightly controlled temporal expression of the IE2 proteins and provides complementation of both growth-impaired and nonviable IE2 mutant viruses. The strategy involves creation of cell lines with separate lentiviruses expressing a bicistronic RNA with a selectable marker as the first open reading frame (ORF) and IE2 86, IE2 60, or IE2 40 as the second ORF. Induction of expression of the IE2 proteins occurs only following DNA recombination events mediated by Cre and FLP recombinases that delete the first ORF. HCMV encodes Cre and FLP, which are expressed at immediate-early (for IE2 86) and early-late (for IE2 40 and IE2 60) times, respectively. We show that the presence of full-length IE2 86 alone provides some complementation for virus production, but the correct temporal expression of IE2 86 and IE2 40 together has the most beneficial effect for early-late gene expression and synthesis of infectious virus. This approach for inducible protein translation can be used for complementation of other mutations as well as controlled expression of toxic cellular and microbial proteins.

Induction of an epithelial integrin alphavbeta6 in human cytomegalovirus-infected endothelial cells leads to activation of transforming growth factor-beta1 and increased collagen production

Human cytomegalovirus (CMV) infection is a major cause of morbidity in immunosuppressed individuals, and congenital CMV infection is a leading cause of birth defects in newborns. Infection with pathogenic viral strains alters cell-cell and cell-matrix interactions, affecting extracellular matrix remodeling and endothelial cell migration. The multifunctional cytokine transforming growth factor (TGF)-beta1 regulates cell proliferation, differentiation, and extracellular matrix remodeling. Secreted as a latent protein complex, TGF-beta1 requires activation before binding to receptors that phosphorylate intracellular effectors. TGF-beta1 is activated by integrin alphavbeta6, which is strongly induced in the epithelium by injury and inflammation but has not previously been found in endothelial cells. Here, we report that CMV infection induces integrin alphavbeta6 expression in endothelial cells, leading to activation of TGF-beta1, signaling through its receptor ALK5, and phosphorylation of its intracellular effector Smad3. Infection of endothelial cells was also found to stimulate collagen synthesis through a mechanism dependent on both TGF-beta1 and integrin alphavbeta6. Immunohistochemical analysis showed integrin alphavbeta6 up-regulation in capillaries proximal to foci of CMV infection in lungs, salivary glands, uterine decidua, and injured chorionic villi of the placenta, demonstrating both its induction in endothelium and up-regulation in epithelium in vivo. Our results suggest that activation of TGF-beta1 by integrin alphavbeta6 contributes to pathological changes and may impair endothelial cell functions in tissues that are chronically infected with CMV.

Functional roles of the human cytomegalovirus essential IE86 protein

The IE86 protein of human cytomegalovirus (HCMV) is unique among viral and cellular proteins because it negatively autoregulates its own expression, activates the viral early and late promoters, and both activates and inhibits cellular promoters. It promotes cell cycle progression from Go/G1 to G1/S and arrests cell cycle progression at the G1/S interface or at G2/M. The IE86 protein is essential because it creates a cellular environment favorable for viral replication. The multiple functions of the IE86 protein during the replication of HCMV are reviewed.

Increased urinary excretion of transforming growth factor-beta(1) in renal transplant recipients during cytomegalovirus infection

AIMS

Cytomegalovirus (CMV) is a suggested risk factor for chronic allograft nephropathy, and transforming growth factor-beta (TGF-beta) is a key fibrogenic molecule in this process. CMV has been shown to induce the expression of TGF-beta and several cytokines. We analyzed the impact of CMV on urinary excretion of TGF-beta, ICAM-1, TNF-alpha and correlated findings with biopsy histology.

MATERIAL

Urine samples from 46 renal transplant recipients were available for the study. Urine samples were taken when CMV infection was suspected, or for controlling of proteinuria or bacteriuria.

METHOD

CMV was diagnosed by antigenemia and viral cultures. Patients with previous CMV infection were excluded from the analysis. Urine samples were analyzed by ELISA-method to detect the levels of TNF-alpha, ICAM-1 and TGF-beta(1). Banff '97 criteria were used for scoring of protocol biopsies taken 6 months after transplantation.

RESULTS

At the time of the urine collection, 13/46 patients had CMV infection. Eight patients with no CMV infection were used as controls. TGF-beta(1) was significantly increased in the CMV group (samples taken mean 137+/-79 days post-transplantation) compared to controls (samples 139+/-64 days post-transplantation) (51.1+/-28.0 vs. 13.3+/-6.7 ng/mmol crea, p<0.001). No differences in the levels of other molecules were recorded. In the biopsies, interstitial fibrosis was significantly increased in the CMV group compared to controls.

CONCLUSIONS

Urinary excretion of TGF-beta(1) was increased in patients during CMV infection. This was associated with increased fibrosis in the biopsies.

Cytomegalovirus enhance expression of growth factors during the development of chronic allograft nephropathy in rats

Cytomegalovirus (CMV) accelerates chronic rejection (CRX) in a model of rat kidney allograft. In this model, the expressions of transforming growth factor beta 1 (TGF-beta), platelet-derived growth factor (PDGF)-AA, PDGF-BB and connective tissue growth factor (CTGF) were investigated with and without CMV. Transplantations were performed under immunosuppression. One group of animals was infected with CMV and the other was left uninfected. The grafts were harvested on days 3-60 after transplantation. Growth factor proteins were demonstrated by immunohistochemistry, and mRNAs by in situ hybridization. A significantly more intense and earlier endothelial TGF-beta (2.4 +/- 0.8 vs. 1.0 +/- 0.0; P < 0.05) and PDGF-AA (1.8 +/- 0.4 vs. 1.0 +/- 0.0; P < 0.05) expressions, confirmed by mRNA hybridization, occurred in the CMV group compared with the noninfected group. PDGF-BB appeared in a few inflammatory cells only. In addition CTGF appeared earlier and has more intense in the CMV group (2.5 +/- 0.6 vs. 1.2 +/- 0.5) and the number of CTGF mRNA-positive fibroblasts (57 +/- 9 vs. 3 +/- 4; P < 0.05) was significantly higher. Thus, CMV enhanced expression of TGF-beta1, PDGF-AA and CTGF during the development of CRX.

Early growth response proteins EGR-4 and EGR-3 interact with immune inflammatory mediators NF-κB p50 and p65

Here, we characterize the basis for the T-cell-specific activity of the human zinc-finger protein early growth response factor 4 (EGR-4). A yeast two-hybrid screen showed interaction of EGR-4 with NF-κB p50. Using recombinant proteins, stable physical complex formation was confirmed for EGR-4 and EGR-3 with p50 and with p65 using glutathione-S-transferase pull-down assays and surface-plasmon-resonance and peptide-spot analyses. In vivo interaction of EGR-4 and EGR-3 with NF-κB p65 was demonstrated by immunoprecipitation experiments and fluorescence-resonance-energy transfer (FRET) analysis showing interaction in the nucleus of transfected Jurkat T cells. In transfection assays, EGR-p50 complexes were transcriptionally inactive and EGR-p65 complexes strongly activated transcription of the promoters of the human genes encoding the cytokines interleukin 2, tissue necrosis factor α and ICAM-1. The EGR-p65 complexes increased reporter-gene activity about 100-fold and thus exceeded the transcriptional activities of the p65 homodimer and the p65/p50 heterodimers. The major interaction domain for p65 was localized within the third zinc finger of EGR-4 using deletion mutants for pull-down assays and peptide-spot assays. By computer modeling, this interaction domain was localized to an α-helical region and shown to have the central amino acids surface exposed and thus accessible for interaction. In summary, in T cells, the two zinc-finger proteins EGR-4 and EGR-3 interact with the specific nuclear mediator NF-κB and control transcription of genes encoding inflammatory cytokines.

Characterization and regulation of essential murine cytomegalovirus genes m142 and m143

US22 gene family members m142 and m143 are essential for replication of murine cytomegalovirus (MCMV). Their transcripts are produced with immediate-early kinetics, but little else is known about these viral genes. Unlike their transcripts, the m142 and m143 gene products (pm142, pm143) were not expressed until early times post-infection, with levels increasing over the course of infection. Both pm142 and pm143 were predominantly cytoplasmic, but cellular fractionation studies confirmed that the proteins were present in the nucleus as well. In addition, pm142 was detected within the virion. Both the m142 and m143 promoters were strongly upregulated by viral infection or by MCMV IE1. However, UV-inactivated virus and IE3 upregulated only the m142 promoter. When tested for transcriptional transactivating activity, neither m142 nor m143 demonstrated significant activity, either alone or in combination with the major immediate-early gene products. This failure to transactivate, along with their essential nature, makes m142 and m143 unique among the immediate-early genes of the US22 gene family.

Persistent cytomegalovirus infection is associated with increased expression of TGF- 1, PDGF-AA and ICAM-1 and arterial intimal thickening in kidney allografts

BACKGROUND

Cytomegalovirus (CMV) is a suggested risk factor for the development of chronic allograft nephropathy. Transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF) are important molecules in this process. We analysed the impact of persistent CMV infection in kidney allografts on the expression of growth factors, adhesion molecules and inflammation markers.

METHODS

In a population of 172 renal transplant recipients, CMV was diagnosed in 82 patients by pp65 antigenaemia test and viral cultures. Biopsies taken after CMV infection were available from 48 of the 82 patients for the demonstration of CMV antigens by immunohistochemistry and in situ DNA hybridization. Biopsy material for further analyses was available from 16 CMV patients. Five patients with no previous CMV infection were used as controls. Biopsy histology was scored according to Banff 97 classification.

RESULTS

In 11 out of 16 patients, persistent CMV antigens and/or DNA were demonstrated in the biopsy >2 months after the last positive finding in blood or urine. Increased expression of TGF-beta1 was recorded in tubuli and in arterial endothelium in biopsies with a positive CMV finding compared with controls. Also, the expression of PDGF-AA was increased in tubuli and somewhat in arterial endothelium in CMV-positive biopsies. The expression of intercellular adhesion molecule-1 (ICAM-1) was increased significantly in peritubular capillary endothelium. Vascular intimal thickening was increased in the biopsies with persistent CMV infection.

CONCLUSIONS

Persistent CMV infection in kidney allografts was associated with increased vascular changes and increased expression of TGF-beta1, PDGF-AA and ICAM-1.

The phosphorylation status of the serine-rich region of the human cytomegalovirus 86-kilodalton major immediate-early protein IE2/IEP86 affects temporal viral gene expression

The 86-kDa major immediate-early protein (IE2/IEP86) of human cytomegalovirus (HCMV) contains a serine-rich region (amino acids 258 to 275) with several consensus casein kinase II (CKII) sites. We performed extensive mutational analysis of this region, changing serines to alternating alanines and glycines. Mutation of the serines between amino acids 266 and 275 eliminated in vitro phosphorylation by CKII. In vitro CKII phosphorylation of the serines between amino acids 266 and 269 or between amino acids 271 and 275 inhibited the ability of IE2/IEP86 to bind to TATA-binding protein. Correspondingly, nonphosphorylatable mutants in these regions showed increased activation of specific HCMV gene promoters in transfection studies. Viruses containing mutations of the serines throughout the entire region (amino acids 258 to 275) or the second half (amino acids 266 to 275) of the region showed delayed expression of all viral proteins tested and, correspondingly, delayed growth compared to wild-type HCMV. Mutation of the serines in the first half of the serine-rich region (amino acids 258 to 264) or between amino acids 266 and 269 propagated very slowly and has not been further studied. In contrast, mutation of the serines between amino acids 271 and 275 resulted in accelerated virus growth and accelerated temporal expression of viral proteins. These results suggest that the serine-rich region is structurally complex, possibly affecting multiple functions of IE2/IEP86. The data show that the phosphorylation state of the serine-rich region, particularly between amino acids 271 and 275, modulates the temporal expression of viral genes.

The putative zinc finger of the human cytomegalovirus IE2 86-kilodalton protein is dispensable for DNA binding and autorepression, thereby demarcating a concise core domain in the C terminus of the protein

The IE2 86-kDa gene product is an essential regulatory protein of human cytomegalovirus (HCMV) with several functions, including transactivation, negative autoregulation, and cell cycle regulation. In order to understand the physiological significance of each of the IE2 functions, discriminating mutants of IE2 are required that can be tested in a viral background. However, no such mutants of IE2 are available, possibly reflecting structural peculiarities of the large and ill-defined C-terminal domain of IE2. Here, we revisited the C-terminal domain by analyzing IE2 mutants for transactivation, DNA binding, autoregulation, and cell cycle regulation in parallel. We found it to contain an unexpectedly concise core domain (amino acids 450 to 544) that is defined by its absolute sensitivity to any kind of mutation. In contrast, the region adjacent to the core (amino acids 290 to 449) generally tolerates mutations much better. Although it contributes more specific sequence information to distinct IE2 activities, none of the mutations analyzed abolished any particular function. The core is demarcated from the adjacent region by the putative zinc finger region (amino acids 428 to 452). Surprisingly, the deletion of the putative zinc finger region from IE2 revealed that this region is entirely dispensable for any of the IE2 functions tested here in transfection assays. Our work supports the view that the 100 amino acids of the core domain hold the key to most functions of IE2. A systematic, high-density mutational analysis of this region may identify informative mutants discriminating between various IE2 functions that can then be tested in a viral background.

Analysis of splice variants of the immediate-early 1 region of human cytomegalovirus

The major immediate-early (MIE) gene of human cytomegalovirus (HCMV) produces multiple mRNAs through differential splicing and polyadenylation. Reverse transcriptase PCR was used to characterize transcripts from exons 1, 2, 3, and 4 (immediate-early 1 [IE1]). The expected IE72 and IE19 mRNAs were detected, as well as two heretofore-uncharacterized transcripts designated IE17.5 and IE9. The IE72, IE19, and IE17.5 transcripts utilized the same 5'-splice site in exon 3. IE9 utilized a cryptic 5'-splice site within exon 3. The IE19, IE17.5, and IE9 transcripts all used different 3'-splice sites within exon 4. These spliced species occur in infected human foreskin fibroblast (HFF) cells, with accumulation kinetics similar to those of IE72 mRNA. IE19 and IE9 RNAs were much more abundant than IE17.5 RNA. Transfection of CV-1 cells with cDNAs resulted in IE19 and IE17.5 proteins detectable by antibodies to either N-terminal or C-terminal epitopes. No IE9 protein product has been detected. We have not been able to detect IE19, IE17.5, or IE9 proteins during infection of HFF, HEL, or U373MG cells. Failure to detect IE19 protein contrasts with a previous report (M. Shirakata, M. Terauchi, M. Ablikin, K. Imadome, K. Hirai, T. Aso, and Y. Yamanashi, J. Virol. 76:3158-3167, 2002) of IE19 protein expression in HCMV-infected HEL cells. Our analysis suggests that an N-terminal breakdown product of IE72 may be mistaken for IE19. Expression of IE19 or IE17.5 from its respective cDNA results in repression of viral gene expression in infected cells. We speculate that expression of these proteins during infection may be restricted to specific conditions or cell types.

Oncomodulatory signals by regulatory proteins encoded by human cytomegalovirus: a novel role for viral infection in tumor progression

A high frequency of human cytomegalovirus (HCMV) genome and antigens in tumor samples of patients with different malignancies is now well documented, although the causative role for HCMV in the development of the neoplasias remains to be established. HCMV infection can modulate multiple cellular regulatory and signalling pathways in a manner similar to that of oncoproteins of small DNA tumor viruses such as human papilloma virus or adenoviruses. However, in contrast to these DNA tumor viruses, HCMV infection fails to transform susceptible normal human cells. There is now growing evidence that tumor cells with disrupted regulatory and signalling pathways enable HCMV to modulate their properties including stimulation of cell proliferation, survival, invasion, production of angiogenic factors, and immunogenic properties. In contrast to previously suggested "hit and run" transformation we suggest that persistence in tumor cells is essential for HCMV to fully express its oncomodulatory effects. These effects are observed particularly in persistent HCMV infection and are mediated mainly by activity of HCMV regulatory proteins. In persistently HCMV-infected tumor cell lines - a selection of novel, slowly growing virus variants with changes in coding sequences for virus regulatory proteins takes place. As a result, oncomodulatory effects of HCMV infection may lead to a shift to more malignant phenotype of tumor cells contributing to tumor progression.

Transforming growth factor beta/Smad3 signaling regulates IRF-7 function and transcriptional activation of the beta interferon promoter

The rapid induction of alpha interferon (IFN-alpha) and IFN-beta expression plays a critical role in the innate immune response against viral infection. We studied the effects of transforming growth factor beta (TGF-beta) and its intracellular effectors, the Smads, on the function of IRF-7, an essential transcription factor for IFN-alpha and -beta induction. IRF-7 interacted with Smads, and IRF-7, but not IRF-3, cooperated with Smad3 to activate IFN-beta transcription. This transcriptional cooperation occurred at the IRF-binding sequences in the IFN-beta promoter, and dominant-negative interference with TGF-beta receptor signaling and Smad3 function decreased IRF-7-mediated transcription. Furthermore, elimination of Smad3 expression in Smad3(-/-) fibroblasts delayed and decreased double-stranded RNA-induced expression of endogenous IFN-beta, whereas restoration of Smad3 expression enhanced IFN-beta induction. The IRF-7-Smad3 cooperativity resulted from the regulation of the transactivation activity of IRF-7 by Smad3, and dominant-negative interference with Smad3 function decreased IRF-7 activity. Consistent with the regulation by Smad3, the transcriptional activity of IRF-7 depended on and was regulated by TGF-beta signaling. Our studies underscore a role of TGF-beta/Smad3 signaling in IRF-7-mediated induction of IFN-beta expression.

Strain variations in single amino acids of the 86-kilodalton human cytomegalovirus major immediate-early protein (IE2) affect its functional and biochemical properties: implications of dynamic protein conformation

The 86-kDa major immediate-early protein, IEP86 (IE2, IE2(579aa), or ppUL122a), from the Towne and AD169 strains of human cytomegalovirus show four amino acid variations, namely, R68Q, K455E, T541A, and seven consecutive serines beginning at position 258 in Towne and eight serines in AD169. A commonly utilized IEP86 cDNA expression clone (herein called the original cDNA) (E. Baracchini, E. Glezer, K. Fish, R. M. Stenberg, J. A. Nelson, and P. Ghazal, Virology 188:518-529, 1992) shows the Towne R68 and seven serines but contains the AD169 E455 and A541 plus two amino acid mutations, M242I and A463T. In transcriptional activation analyses using several promoters, the IEP86 produced by the original cDNA was 40 to 60% less active than wild-type (WT) Towne IEP86, whereas AD169 IEP86 was two to three times more active than WT Towne IEP86. To determine which amino acid variations or mutations accounted for the differences in transcriptional activation, they were individually tested in the WT Towne IEP86 background. K455E, M242I, and the eighth serine had little effect on transcriptional activation or sumoylation when inserted into the Towne background. T541A significantly increased transcriptional activation on all promoters tested and showed increased sumoylation; T541A is the primary reason that WT AD169 IEP86 has increased activity over WT Towne IEP86. The increased sumoylation seen with T541A was quantitatively reduced to WT Towne levels when the K455E alteration was present, suggesting that K455 may be a sumoylation site or that E455 may cause alterations in the IEP86 structure which affect overall sumoylation. A463T was very deleterious to transcriptional activation and caused reduced sumoylation. The A436T mutation in the original cDNA is partially compensated by the presence of the T541A variation. Phosphopeptide mapping suggests that a threonine at 463 or 541 does not introduce a phosphorylation site. However, the A463T mutation does affect phosphorylation at a distant site, suggesting that it alters the conformation of the protein. Promoter-specific effects were noted with some of the amino acid variations, particularly T541A. Structural modeling is presented which suggests how A463T and T541A alter the functional structure of WT Towne IEP86. A hydrophobic core containing A463 is predicted to be responsible for the functional integrity of the carboxy-terminal region of IEP86 between amino acids 344 and 579.

Early growth response proteins (EGR) and nuclear factors of activated T cells (NFAT) form heterodimers and regulate proinflammatory cytokine gene expression

Activation of transcription factors by receptor mediated signaling is an essential step for T lymphocyte effector function. Following antigenic stimulation of T cells the two central cytokines IL-2 and TNFalpha are co-expressed and co-regulated. Two important transcription factors, i.e., early growth response (EGR) protein EGR-1 and nuclear factors of activated T cells (NFAT) protein NFATc, regulate transcription of the human IL-2 cytokine and the same combination of EGR and NFAT proteins seems relevant for coordinated cytokine expression. Here we demonstrate that the zinc finger protein EGR-1 and two members of the NFAT protein family bind simultaneously to adjacent elements position -168 to -150 within the TNFalpha promoter. Both promoter sites are important for TNFalpha gene transcription as shown by transfection assays having the IL-2 and TNFalpha promoters linked to a luciferase reporter. The use of promoter deletion constructs with the zinc finger protein (ZIP), the NFAT binding element or a combination of both deleted show a functional cooperation of these elements and of their binding factors. These experiments demonstrate that EGR-1 as well as EGR-4 functionally cooperate with NFAT proteins and induce expression of both cytokine genes. Using tagged NFATc and NFATp in glutathione S-transferase pull down assays showed interaction and physical complex formation of each NFAT protein with recombinant, as well as native, EGR-1 and EGR-4 proteins. Thus EGR-NFAT interaction and complex formation seems essential for human cytokine expression as adjacent ZIP and NFAT elements are conserved in the IL-2 and TNFalpha gene promoters. Binding of regulatory EGR and NFAT factors to these sites and the functional interaction and formation of stable heterodimeric complexes indicate an important role of these factors for gene transcription.