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PubMed1975

Deoxyribonucleic acid fiber autoradiography as a technique for studying the replication of the mammalian chromosome.

Deoxyribonucleic acid (DNA) fiber autoradiography is a technique that allows analysis of replication events on mammalian chromosomal DNA. 3H-thymidine is used to pulse-label DNA, which is subsequently released from lysed cells and extended linearly over a glass slide. Autoradiograms are produced by exposing the labeled DNA to light-sensitive emulsion. The effects of inhibition of protein synthesis on DNA replication were examined using this technique. Analysis of the autoradiographic patterns has shown that inhibition of protein synthesis with either cycloheximide or puromycin retards the rate of replication fork progression. In addition, these antibiotics after the normal pattern of multifocal initiation on replication units. The spatial interval between active initiation sites is decreased, there is a decay in synchrony of initiation events on subchromosomal clusters of replication units, the decay in synchrony of initiation events on subchromosomal clusters of replication units, the frequency of initiation is inhibited and the frequency of units showing the normal bidirectional mode of replication is decreased. The retarded fork progression and shorter initiation intervals may result either from the continued operation of a subset of replication units resistant to the inhibition of protein synthesis, or be manifestations of the inhibition of protein synthesis on all active sites. The other alterations, decreased synchrony and frequency of initiation and increased unidirectional replication probably occur on all active units when protein synthesis is inhibited.

Autoradiography↗
PubMed1988

Effects of platelet-derived growth factor and somatomedin-C/insulin-like growth factor I on the deoxyribonucleic acid replication of fetal rat islets of Langerhans in tissue culture.

The effects of platelet-derived growth factor (PDGF) on DNA replication and release of insulin and somatomedin-C/insulin-like growth factor I (SM-C/IGF-I) from cultured fetal rat islets have been studied. In medium containing 1% fetal calf serum and 16.7 mM glucose, both PDGF (2-10 ng/ml) and SM-C/IGF-I (100 ng/ml) stimulated DNA replication 2-fold. The growth stimulatory effects of the two peptides were additive. In the absence of serum, SM-C/IGF-I, but not PDGF, stimulated DNA replication. Under conditions of PDGF-stimulated DNA replication there was no increased release of either insulin or SM-C/IGF-I into the culture medium. An antibody against SM-C/IGF-I which inhibited SM-C/IGF-I-stimulated DNA replication did not affect PDGF-stimulated DNA replication. Similarly, an antibody against PDGF did not affect DNA replication stimulated by SM-C/IGF-I. It is concluded that PDGF stimulates islet cell DNA replication. This is the first demonstration of a tissue of nonmesodermal origin responding to PDGF. Stimulation of DNA replication appears to be independent of SM-C/IGF-I release, and furthermore, the results indicate that the islets do not produce PDGF-like substances themselves. It is suggested that PDGF is of importance for fetal islet development.

Animals↗
PubMed2004

Stable chromosomal units determine the spatial and temporal organization of DNA replication.

DNA replication occurs in mammalian cells at so-called replication foci occupying defined nuclear sites at specific times during S phase. It is an unresolved problem how this specific spatiotemporal organization of replication foci is determined. Another unresolved question remains as to what extent DNA is redistributed during S phase. To investigate these problems, we visualized the replicating DNA and the replication machinery simultaneously in living HeLa cells. Time-lapse analyses revealed that DNA was not redistributed to other nuclear sites during S phase. Furthermore, the results showed that DNA is organized into stable aggregates equivalent to replication foci. These aggregates, which we call sub-chromosomal foci, stably maintained their replication timing from S phase to S phase. During S-phase progression, the replication machinery sequentially proceeded through spatially adjacent sets of sub-chromosomal foci. These findings imply that the specific nuclear substructure of chromosomes and the order of their stable subunits determine the spatiotemporal organization of DNA replication.

Animals↗
PubMed1992

Dynamics of three-dimensional replication patterns during the S-phase, analysed by double labelling of DNA and confocal microscopy.

The temporal and spatial progression of DNA replication in interphase nuclei of eukaryotic cells has been investigated. Application of a recently developed technique for the immunofluorescence double staining of cell nuclei labelled first with iododeoxyuridine (IdUrd) and subsequently with chlorodeoxyuridine (CldUrd) allows the visualization of two replication patterns in the same nucleus originating from two different periods of the S-phase. We have analysed changes in the three-dimensional replication patterns during the S-phase. To record dual colour three-dimensional images of doubly stained nuclei, a confocal microscope is used. This CSLM is equipped with a specific laser/filter combination to collect both fluorescence signals (FITC and Texas Red) in a single scan, thus precluding pixel shift between the images. A method for the quantitative evaluation of the degree of overlap between DNA regions replicated in two different periods of the S-phase is applied. The results confirm the generally accepted theory that DNA is replicated coordinately in a specific temporal order during the S-phase. The replication time of a DNA domain (i.e. the time between initiation and termination of DNA replication within a domain) at the very beginning of the S-phase was known to be one hour (Nakamura et al., 1986). Our observations show that in the rest of the S-phase, the replication time of a DNA region is also about one hour. We conclude that replicon clusters located in the same region are replicated in the same relatively short period of time. After this period there is no unreplicated DNA left in this region.

Animals↗
PubMed1999

DNA replication and nuclear organization: prospects for a soluble in vitro system.

The role of nuclear structure in the replication of eukaryotic DNA has been the subject of debate for many decades. The recent demonstration that once-per-cell-cycle replication can take place in vitro without a nucleus, providing sufficiently high concentrations of replication factors are supplied, suggests that one role of the nucleus is to concentrate essential factors. This important finding has paved the way for the establishment of a purified biochemical system for replication of eukaryotic DNA. However, this soluble system, derived from Xenopus egg extracts, initiates replication within any DNA sequence and does not recapitulate the spatial and temporal regulation of DNA replication that is observed in most cells. In both Xenopus and Drosophila embryos, site-specific initiation of replication is not observed until after nuclei become transcriptionally active at the blastula stage of development. Furthermore, programmed changes in both the locations of origins and the time during S-phase at which sequences are replicated accompany key stages of metazoan development. Recent findings indicate that these changes correlate with changes in nuclear organization and that the spatial and temporal program for replication is established early in G1-phase when nuclei are structurally and functionally reorganized after mitosis.

Animals↗
PubMed2005

The MCM complex: its role in DNA replication and implications for cancer therapy.

The MCM complex controls the once per cell cycle DNA replication in eukaryotic cells. In a process known as DNA replication licensing, it primes chromatin for DNA replication by binding origins of DNA replication during the late M to early G1 phase of the cell cycle. Activated by S phase promoting protein kinases, the origin-bound MCM complexes unwind the double stranded DNA at the origins, recruit DNA polymerases and initiate DNA synthesis. Coupled with the initiation of DNA replication in the S phase, the MCM complexes move away from replication origins as a component of the DNA replication fork, likely serving as DNA helicases. Their departure deprives replication origins the ability to re-initiate DNA replication for the reminder of the cell cycle. Because of its vital role in genome duplication in proliferating cells, deregulation of the MCM function results in chromosomal defects that may contribute to tumorigenesis. The MCM proteins are highly expressed in malignant human cancers cells and pre-cancerous cells undergoing malignant transformation. They are not expressed in differentiated somatic cells that have been withdrawn from the cell cycle. Therefore, these proteins are ideal diagnostic markers for cancer and promising targets for anti-cancer drug development. In this article, I will overview the structures and functions of the MCM complex with an effort to integrate insights from recent biochemical and structural studies. Discussions will also cover activities and structures of the complex that may be useful for the development of drug screens.

Animals↗
PubMed2005

Changes in replication, nuclear location, and expression of the Igh locus after fusion of a pre-B cell line with a T cell line.

We have previously observed that replication and nuclear location of the murine Igh locus are developmentally regulated during B cell differentiation. In non-B, B, and plasma cells, sequences near the 3' end of the Igh locus replicate early in S while upstream Vh sequences replicate late in S, and the Igh locus is located near the nuclear periphery. In fact, in MEL non-B cells, replication of a 500-kb segment containing Igh-C and flanking sequences occurs progressively later throughout S by 3' to 5' unidirectional fork movement. In contrast, in pro- and pre-B cells, the entire 3-Mb Igh locus is located away from the nuclear periphery and replicates early in S by forks progressing in both directions. In this study, using an 18-81 (pre-B) x BW5147 (T) cell fusion system in which Igh expression is extinguished, we found that in all Igh alleles, Vh sequences replicated later in S than 3' Igh sequences (similar to that detected in BW5147), but the Igh locus was situated away from the nuclear periphery (similar to that observed in 18-81). Thus, pre-B cell-derived Igh genes had changes in replication timing, but not in nuclear location, whereas T cell-derived Igh genes changed their nuclear location but not their replication timing. These data are consistent with the silencing of a pre-B cell-specific replication program in the fusion hybrid cells and independent regulation of the nuclear location of Igh loci.

Animals↗
PubMedDate not supplied

DNMT1 is a component of a multiprotein DNA replication complex.

DNA methylation is a major determinant of epigenetic inheritance and plays an important role in genome stability. The accurate propagation of DNA methylation patterns with cell division requires that methylation be closely coupled to DNA replication, however the precise molecular determinants of this interaction have not been defined. In the present study, we show that the predominant DNA methyltransferase species in somatic cells, DNMT1, is a component of a multiprotein DNA replication complex termed the DNA synthesome that fully supports semi-conservative DNA replication in a cell-free system. DNMT1 protein and activity were found to co-purify with the human DNA synthesome through a series of subcellular fractionation and chromatography steps, resulting in an enrichment of methyltransferase specific activity from two human cell lines. DNA methyltransferase activity co-eluted with in vitro replication activity and DNA polymerase alpha activity on sucrose density gradients suggesting that DNMT1 is a tightly bound, core component of the replication complex. The synthesome-associated pool of DNA methyltransferase exhibited both maintenance and de novo methyltransferase activity and the ratio of the two was similar to that observed in whole cell lysates and for recombinant DNMT1. These data indicate that interactions within the synthesome complex do not influence the intrinsic preference of DNMT1 for hemimethylated DNA, but suggest that newly replicated DNA may be subject to low level de novo methylation. The data indicate that DNA methylation is tightly coupled to replication through physical interaction of DNMT1 and core components of the replication machinery. The definition of the molecular interactions between DNMT1 and other proteins in the replication complex in normal and neoplastic cells will provide further insight into the regulation of DNA methylation and the mechanisms underlying the alteration of DNA methylation patterns during carcinogenesis.

Cell Division↗
PubMed2005

Chromatin remodeling by WSTF-ISWI at the replication site: opening a window of opportunity for epigenetic inheritance?

During DNA replication, chromatin states have to be accurately transmitted from the parental to the daughter strands for faithful epigenetic inheritance. Chromatin remodelling factors at the replication site are thought to be involved in this process. Recent work adds ATP-dependent nucleosome remodelling factors to this category of enzymes. The WICH complex, consisting of the ISWI-type ATPase SNF2H and the Williams Syndrome Transcription Factor (WSTF), binds to replication foci using PCNA, a key factor in DNA- and chromatin replication and DNA repair, as an interaction platform. Depletion of WSTF results in decreased chromatin accessibility, which is evident already in newly replicated DNA. This leads to heterochromatin formation on a global scale and a decrease in overall transcriptional activity. Here, we propose that WICH, by keeping nucleosomes mobile, provides access to the newly replicated DNA and may thereby create a window of opportunity after DNA replication for rebinding of factors that maintain the epigenetic state, and thus prevents aberrant heterochromatin formation. Our model may provide an explanation for the long-standing observation of a delay in chromatin "maturation" on newly replicated DNA, by connecting this delay with the action of PCNA-bound WSTF-ISWI, and highlights chromatin remodeling shortly after DNA replication as a critical point for regulation.

Adenosine Triphosphatases↗
PubMed2026

Replication stress links Geminin depletion to centrosome amplification.

The timing of DNA replication and centrosome duplication is tightly regulated with cell cycle progression to ensure the faithful duplication of the genome during cell division. Both DNA and centrosomes are licensed for replication in late telophase/early G1, replicated in S phase and segregated during mitosis; yet how defects in DNA replication licensing are coupled to centrosome homeostasis remains poorly understood. Here, we show that depletion of the replication licensing inhibitor Geminin in proliferating mouse embryonic fibroblasts induces robust centrosome amplification together with impaired primary cilium assembly. Rather than promoting whole-genome reduplication, knockdown of Geminin triggers a replication stress response, characterized by DNA damage accumulation throughout the cycle, and activation of an ATR-dependent DNA damage response. Mechanistically, Geminin depletion-induced replication stress activates the ATR-Chk1-Wee1 checkpoint axis prolonging G2 and leading to premature centriole disengagement and centrosome amplification. These findings identify replication stress as the signaling module that couples defective DNA replication licensing to centrosome amplification.

DNA damage↗
PubMed2001

CD8+ T cell suppressor factors and the control of infection, replication and transcription of human immunodeficiency virus.

CD8+ T cells have been shown to produce factors which modulate HIV-1 replication in both T cells and monocytic cells. Examination of the literature reveals that this modulation may occur by the production of beta-chemokines which block viral entry. However, another CD8+ T cell-derived factor(s) targets the replication of HIV-1 at the level of transcription. CD8+ T cell factors strongly suppress replication at the level of transcription in T cells and T cell lines, the factors enhance both replication and transcription in cells of the monocyte/macrophage lineage. The enhancement of transcription and replication, which is pertussis toxin sensitive is induced by increased production of TNF-alpha by the target cells. Thus, CD8+ T cells produce factors which mediate effects on transcription and replication of HIV-1 in a cell type-dependent manner. In this review a summary of the effects of chemokines and CD8-derived factors on HIV-1 transcription and replication is presented focusing on the cellular pathways which may mediate their effects on HIV transcription and replication in different cell types. The virus-host cell interactions that participate in the persistent replication of HIV in macrophages and the suppression of these functions in T cells require definition. The identification of CD8+ T cell factors which exert these controls on HIV-1 may lead to promising new therapies for HIV infection.

Anti-HIV Agents↗
PubMed2001

Treatment of malignant gliomas with a replicating adenoviral vector expressing herpes simplex virus-thymidine kinase.

We evaluated the interaction between oncolytic, replication-competent adenoviral vectors and the herpes simplex virus-1 thymidine kinase (HSV1-tk) gene/ganciclovir (GCV) suicide system for the treatment of malignant gliomas. We constructed a panel of replication-competent adenoviral vectors in which the luciferase (IG.Ad5E1(+). E3Luc) or HSV1-tk gene (IG.Ad5E1(+).E3TK) replace the M(r) 19,000 glycoprotein (gp19K) coding sequence in the E3 region. IG.Ad5E1. IG.Ad5.ClipLuc and IG.AdApt.TK are E1-deleted viruses that contain the luciferase or the HSV1-tk gene in the former E1 region driven by the human cytomegalovirus promoter. IG.Ad5. Sarcoma 1800HSA.E3Luc contains an irrelevant gene in the E1 region, whereas the gp19K coding sequence in the E3 region is replaced by the luciferase gene as in the replicating virus IG.Ad5E1(+).E3Luc. For in vitro experiments, we used a panel of human glioma cell lines (U87 MG, T98G, A172, LW5, and U251), a rat gliosarcoma cell line (9 L), and human lung (A549) and prostate carcinoma (P3) cell lines. In vitro, GCV sensitivity (10 microg/ml) was studied in U87 MG cells after infection at a multiplicity of infection of 1 and 10. A s.c. U87 MG glioma xenograft model was established in NIH-bg-nu-xid mice. Tumors of 100-150 mm(3) were treated with a single injection of adenovirus 10(9) IU suspended in 100 microl of PBS, and GCV 100 mg/kg was administered i.p. twice daily for 7 days. The cytopathic effect of all three replication-competent adenoviral vectors was similar to the cytopathic effect of wild-type adenovirus 5 on all human cell lines tested, indicating that deletion of the E3 gp19K sequences did not affect the oncolytic effect of the vectors. In vitro, luciferase expression was the same for both E1-deleted vectors (IG.Ad5.ClipLuc and IG.Ad5. Sarcoma 1800HSA.E3Luc), demonstrating the strength of the internal E3 promoter even in the absence of E1A. However, in vitro expression levels obtained with replication-competent IG.Ad5E1(+). E3Luc were 3 log higher (allowing infection with a 2-3-log lower multiplicity of infection) in the human cell lines. In U87 MG glioma cells, the oncolytic effect of replication-competent IG.Ad5E1(+).E3TK was significantly enhanced by the addition of GCV and greatly exceeded the cytotoxicity of replication-incompetent IG.AdApt.TK combined with GCV. In established s.c. U87 MG glioma xenografts, a single injection of IG.Ad5E1(+).E3TK resulted in a significant slowing of tumor growth and prolonged survival compared with injection of IG.AdApt.TK. Addition of GCV slowed tumor growth, further adding to survival. In conclusion, the oncolytic effect of replicating adenoviral vectors and HSV1-tk/GCV have potent antitumor effects in gliomas. When combined, these two approaches are complementary, resulting in a significantly improved treatment outcome. In addition, replication-competent adenoviral vectors missing the E3 gp19K coding sequences, have oncolytic efficacy comparable with wild type. In combination with high expression levels obtained with the natural E3 promoter, such vectors are promising new anticancer agents.

Adenoviridae↗
PubMedDate not supplied

The essence of replication timing: determinants and significance.

In eukaryotic organisms, chromosomal DNA replication initiates at multiple sites on the chromosome at different times, following a temporal replication program. Though it is intriguing that all eukaryotic cells possess a temporal replication program that is conserved from one cell cycle to the next, it is not known whether this program is essential for the replication process per se, what specifies the temporal replication program, or whether there is a causal relationship between replication timing and other nuclear processes such as transcription. Emerging studies suggest that replication timing may indeed precede and dictate other cellular processes involving chromatin. Moreover, a systematic correlation between altered replication timing and cancer development has been observed. These studies suggest that replication timing may be an important feature of genome organization with vital functional significance.

Animals↗
PubMed2003

Proteasome inhibitors: a novel tool to suppress human cytomegalovirus replication and virus-induced immune modulation.

Recently, we like others, demonstrated that systemic inflammation is the most important mechanism involved in (re)activation of human cytomegalovirus (HCMV) in both immunocompetent patients. By in vitro studies the eukaryotic transcription factor NF-kappaB could be identified as the key mediator of TNF-alpha- and IE1-dependent stimulation of the HCMV IE1/2 enhancer/promoter activity, which is crucial for initiation of viral gene expression during reactivation from latency as well as productive infection. The enzymatic proteasome complex plays a central role in regulating intracellular processes, including the activation of NF-kappaB. As present antiviral strategies target mainly late events in HCMV replication (DNA replication, virus assembly) that do not completely prevent virus mediated immunopathogenesis, we wondered whether proteasome inhibitors might be a novel tool for targeting the interaction between inflammation and HCMV (re)activation. Here, proteasome inhibitors like MG132, PSI, II and III (MG262) have been shown to block both TNF-alpha-associated up-regulation of the HCMV IE1/2 enhancer/promoter in monocytic cells in an in vitro transient transfection system and HCMV replication in permissive embryonal fibroblasts. Importantly, ganciclovir-resistant HCMV strains are sensitive to proteasome inhibitors. The effect of proteasome inhibitors on HCMV replication was found to be specific as replication of other herpes viruses, like HSV-1 and HSV-2, under identical experimental conditions was not influenced. Inhibition of HCMV replication correlated with a delayed and significantly reduced expression of IE proteins, particularly of the IE2 protein, suggesting that MG132 blocks HCMV replication at an immediate early stage of infection. Early and late protein synthesis as shown exemplary for the pp52 (DNA-binding protein) and p68 (structural protein) protein production and viral DNA synthesis were also inhibited. Suppression of HCMV replication could be correlated with an increased cytosolic accumulation of IkappaB as well as a reduced NF-kappaB binding activity in nuclear extracts of MG132-treated cells, which mainly regards NF-kappaB p50. MG132 also reduced the immune modulatory activity of the virus by abrogating virus-induced up-regulation of cellular ICAM-1. These data suggest that short-term therapy with proteasome inhibitors might be an alternative strategy to prevent (re)activation, replication and immune modulatory activity of HCMV in patients with systemic inflammation.

Chemokine CCL5↗
PubMed2004

[High resolution analysis of replication foci by conventional fluorescent microscopy. I. A study of complexity and DNA content of the foci].

Newly replicated DNA segments (RDS) have been shown to form discrete foci in the mammalian nucleus. Comparison of the number of such foci in formaldehyde-fixed cell nucleus with estimated number of simultaneously active replication forks (RF) suggests that each replication focus contains a cluster of about 10 to 20 closely associated RF. That implied the cluster of synchronously activated replicons as the primary unit of mammalian DNA replication. It still remains unclear whether such clustering of RF does mean adjacency of the replicons in a genomic location (structural clustering, model 1), or it arises from transient clustering of the replicons from different DNA domains at the functioning replication machinery (functional clustering, model 2). In this study we used conventional fluorescence microscopy of the hypotonically treated nuclei preparations to investigate replication foci at the optical resolution limit. Human K562 cells were labeled with 5'-iododeoxyuridine for different time periods. We synchronized the cell culture with hydroxyurea to be able to measure an average increase in DNA content during labeling period using DNA cytometry. Under these conditions, RDS appear as multiple small foci (mini-foci, MF). Further studies revealed that most of such mini-foci of replication represent optical diffraction spots, which are standard in size and different in brightness. The number of the "spots" and variation of their brightness mostly depend on the extent of hypotonic treatment. Flow cytometry control of the synchronized cells peak movement allowed us to measure mean DNA content of the MF. In case of most effective hypotonic treatment, a MF contains about 40 Kbp of labeled DNA, and the general number of the MF approaches the number of replicons that are simultaneously active in a given moment of S-phase. Influence of the effect of hypotonic treatment on overall number of observed MF suggests that replication foci in early and mid S-phase cells do not represent stable structures, but rather arise from functional clustering of comparatively distant replicating regions, thus supporting model 2.

Cell Line, Tumor↗
PubMed2005

[Effect of replication- competent adenovirus-mediated interleukin- 12 gene to chemotherapeutic sensitivity on gastric cancer cell].

OBJECTIVE: To investigate the effect of replication-competent adenovirus-mediated interleukin-12 gene to chemotherapeutic sensitivity on gastric cancer cell. METHODS: Replication-competent adenovirus and replication-competent adenovirus- mediated interleukin- 12 gene was constructed and expanded separately. The mortality of gastric cancer cell caused by the CNHK200- mIL- 12, Onyx- 015 in combination with different dosages of chemotherapeutic agents were evaluated by MTT assay at the same viral titer with a series of different dosages of chemotherapeutic agent,or at a series of different viral titers with the same dosage of chemotherapeutic agent. The curative effect to the xenografts gastric tumor in nude mouse was also observed by two viruses solely or together with 5-Fu. RESULTS: The lytic activity of replication-competent adenovirus to gastric cancer cell line SGC-7901 was relatively poor at MOI value of 0.5, but it could be improved significantly when combined with chemotherapeutic agents of ADM, 5-Fu or CAP compared to the simple chemical therapy (P< 0.05). Chemotherapeutic agent 5- Fu could not effectively kill SGC-7901 when used at a relatively low dosage of 10microg/ml,whereas its activity could be improved when combined with a replication-competent adenovirus,and the killing rate was much higher than that with replication-competent adenovirus solely (P< 0.05). The gastric tumor xenografts was prevented and killed by replication adenovirus solely or combined with 5-Fu. CONCLUSION: The replication- competent adenovirus- mediated interleukin- 12 gene can increase the chemotherapeutic sensitivity on gastric cancer cell. There is synergetic effect between the replication adenovirus and the chemotherapeutic agents in killing gastric cancer cell.

Adenoviridae↗
PubMed2006

[On the role of liver-enriched transcription factors in regulating HBV transcription and replication].

OBJECTIVE: To investigate the effects of various liver-enriched transcription factors in regulating HBV transcription and replication, and to explore their potential roles in HBV hepatotropism. METHODS: The replication-competent HBV recombinant plasmid pHBV4.1 plus different liver-enriched transcription factor (HNF1, HNF3, HNF4, HNF6, C/EBP and RXRa/PPARa) expression plasmids were co-transfected into nonhepatic cell lines (NIH3T3, HeLa, 293T, SW1353, CV-1 and COS1). The transcription levels of 3.5 kb, 2.4/2.1 kb and 0.7 kb HBV RNA were analyzed by Northern blot hybridization, and the level of HBV DNA replication intermediates was detected by Southern blot hybridization analysis. RESULTS: In the absence of co-transfected liver enriched transcription factor expression vectors, the 3.5 kb HBV RNA is not transcribed and HBV DNA replication is not detected after transfecting of NIH 3T3 cells with pHBV4.1. Expression of the liver-enriched transcription factor HNF4 or RXRalpha/PPARalpha, stimulates the transcription of 3.5 kb HBV RNA and the replication of HBV DNA. In contrast, expression of HNF1, HNF3, HNF6 and C/EBP does not stimulate the transcription of 3.5 kb HBV RNA and therefore does not activate viral replication. HNF4 and RXRalpha/PPARalpha were also shown to activate the transcription of 3.5 kb HBV RNA and viral replication in divers cell types including HeLa, 293T, SW1353, CV-1 and COS1 cells. Mutation of the proximal nucleocapsid HNF4 binding site results in a greatly decreased level of HNF4 or RXRalpha/PPARalpha dependent HBV replication. CONCLUSION: This study demonstrated that the liver-enriched transcription factors HNF4 and RXRa/PPARa can support HBV transcription and replication in nonhepatic cells, indicating that liver-specific gene transcription is one of the determinants of HBV hepatotropism.

Animals↗
PubMed1976

Replication of herpes simplex virus in mouse spleen cell cultures stimulated by lipopolysaccharide.

Replication of HSV was demonstrated in spleen cell cultures of D2 and several other strains of mice after prestimulation with mitogenic doses of LPS for 2 days. No viral replication occurred in unstimulated cultures or in cultures prestimulated with PHA and Con A, whereas there was some viral replication in spleen cell cultures of D2 mice after prestimulation with Poly I-C. Spleen cells of B6 mice did not support replication of HSV under any of the conditions we have tested thus far. The reasons for this defect are not clear, but it was obviously not caused by a defective lymphoproliferative response to LPS or by an active anti-viral principle elaborated by B6 spleen cells. F1 hybrids between B6 and D2 mice were capable of HSV replication to the same extent as were spleen cells of D2 mice. Several strains of both HSV-1 and HSV-2 could be replicated in D2 spleen cells cultures. Nylon column treatment of D2 spleen cells removed the ability to replicate HSV, whereas macrophage removal from the spleens by plastic adherence was without effect. Purified peritoneal exudate cells from D2 mice did not support replication of HSV. Together these data suggest that B cells activated by LPS represent the target cell of HSV replication in mouse spleen cell cultures.

Animals↗