Experimental studies on the antiviral agent famciclovir in Behçet's disease symptoms in ICR mice

BACKGROUND

Chronic oral aphthae, recurrent genital ulcers and uveitis are the three main manifestations of Behçet's disease (BD). The aetiopathogenesis of BD is still obscure, but herpes simplex virus (HSV) is one of the possible causal factors. Various kinds of drugs, including immunosuppressants and aciclovir have been used in treatment, but effectiveness is variable.

OBJECTIVES

To demonstrate the efficacy of famciclovir, an antiviral compound that acts against HSV, varicella-zoster virus and hepatitis B virus, in a murine model of BD.

METHODS

Using the HSV-induced BD mouse model, famciclovir was administered variously before and after inoculation or from the day of lesion occurrence, with appropriate controls. Ulceration of the mouth and genital skin and eye involvement were monitored. In addition, spleen cytokine expression was measured by polymerase chain reaction.

RESULTS

Pretreatment and concurrent treatment did not affect the occurrence of BD, but treatment from the appearance of lesions was effective in improving BD and preventing recurrence. After famciclovir, interleukin 2 expression correlated with the recurrence of BD symptoms.

CONCLUSIONS

This model suggests the possible role of immune response to viral infection in the development and activation of BD. The study provides a rationale for clinical trials of famciclovir in the human form of BD.

Radicicol binding to Swo1/Hsp90 and inhibition of growth of specific temperature-sensitive cell cycle mutants of fission yeast

A panel screening using cdc mutants of Schizosaccharomyces pombe identified radicicol as a potent growth inhibitor of certain mutants at the permissive temperature. The strains sensitive to radicicol were cdc7, cdc11, and cdc14, all of which are defective in early septum formation. Cytokinesis but not nuclear division of these mutants was inhibited by radicicol, but that of cells with the wild-type background was not. A biologically active derivative of radicicol with a biotin moiety at the C-11 position bound Swo1, an Hsp90 homologue in S. pombe. Increased Swo1 expression partially suppressed radicicol sensitivity of cdc14 and almost completely rescued morphological abnormalities in cdc14 and cdc7 cells induced by radicicol at the permissive temperature. On the other hand, the increased Swo1 expression did not restore septum formation at the nonpermissive temperature. These results suggest that Swo1, as a molecular chaperone, plays a role in stabilizing these temperature-sensitive proteins at the permissive temperature or in activating the cytokinesis signaling cascade.

Age-related increase of brain cyclooxygenase activity and dietary modulation of oxidative status

Several studies have demonstrated that inhibitors of cyclooxygenase (COX) attenuate various neuronal injuries and age-dependent demented conditions. From these findings, we proposed to test the effect of age on COX activity and its possible suppression by the antiaging action of dietary restriction in the rat brain. The status of reactive oxygen species (ROS) was also assessed to correlate with COX activity to delineate the underlying mechanism of the altered COX activity during aging. These results showed that COX activity significantly increased in 24-month-old rats compared with 6-month-old rats in an ad libitum group. Interestingly, mRNA and protein levels of COX-2 showed little corresponding age-related change. The formation of ROS was found to increase gradually with age in ad libitum fed rats. However, dietary restriction suppressed the increase at the age of 24 months. To substantiate the relationship between ROS and COX activity when the rats were 24 months of age, we conducted in vitro experiments with a C6 glioma cell line. Together, it is concluded that increased COX activity with age is due to the activation of COX catalytic reaction by ROS without increased gene expression of COX-2 and that it is related to the increased pro-oxidant status in aged rats.

Induction of cell cycle arrest and apoptosis in human breast cancer cells by quercetin

Quercetin, a widely distributed bioflavonoid, has been shown to induce growth inhibition in certain cancer cell types. In the present study we have pursued the mechanism of growth inhibition in MCF-7 human breast cancer cells. Quercetin treatment resulted in the accumulation of cells specifically at G2/M phase of the cell cycle. Mitotic index measured by MPM2 staining clearly showed that cells were transiently accumulated in M phase, 24 h after treatment. The transient M phase accumulation was accompanied by a transient increase in the levels of cyclin B1 and Cdc2 kinase activity. However, 24 h or longer treatment caused a marked accumulation of cells in G2 instead of M phase. Levels of cyclin B1 and cyclin B1-associated Cdc2 kinase activity were also decreased. We also found that quercetin markedly increased Cdk-inhibitor p21CIP1/WAF1 protein level after treatment for 48 h or longer, and the induction of p21CIP1/WAF1 increased its association with Cdc2-cyclin B1 complex, however, up-regulation of p53 by quercetin was not observed. Quercetin also induced significant apoptosis in MCF-7 cells in addition to cell cycle arrest, and the induction of apoptosis was markedly blocked by antisense p21CIP1/WAF1 expression. The present data, therefore, demonstrate that a flavonoid quercetin induces growth inhibition in the human breast carcinoma cell line MCF-7 through at least two different mechanisms; by inhibiting cell cycle progression through transient M phase accumulation and subsequent G2 arrest, and by inducing apoptosis.

Application of nucleotide sequence of RNA polymerase beta-subunit gene (rpoB) to molecular differentiation of serovars of Salmonella enterica subsp. enterica

To establish a molecular differentiation method for Salmonella enterica subsp. enterica, a hyper-variable region of RNA polymerase beta-subunit (rpoB) of S. enterica subsp. enterica (I), serotype Typhimurium, and Escherichia coli were investigated through comparison of nucleotide sequence of the region. The hyper-variable region was identified at 612-937 of the gene. After PCR amplification of the region in the 17 serotypes and two biotypes of serotype Gallinarum of S. enterica subsp. enterica (I), the nucleotide sequences of the region were determined and compared. All serotypes were distantly related to E. coli with 82.8-84.7% identities in nucleotide sequence while showing 96.6-100% identities with each other. According to the phylogenetic analysis based on the sequenced region with the neighbor-joining method, relatedness of biotype Gallinarum to serotype Enteritidis and biotype Pullorum was determined. Biotype Gallinarum was more closely related to serotype Enteritidis than biotype Pullorum. These results suggested that the 612-937 variable region of rpoB might be useful for molecular evolutionary analysis of serotypes of S. enterica subsp. enterica (I).

Molecular authentication of Panax ginseng species by RAPD analysis and PCR-RFLP

In order to develop convenient and reproducible methods for the identification of ginseng drugs at a DNA level, randomly amplified polymorphic DNA (RAPD) and PCR-restriction fragment length polymorphism (PCR-RFLP) analyses were applied within Panax species. To authenticate Panax ginseng among ginseng populations, RAPD analysis was carried out using a 20 mer-random primer. The similarity coefficients among the DNA of ginseng plants analyzed were low, ranging from 0.197 to 0.491. In addition, by using PCR-RFLP analysis, very different fingerprints were obtained within Korean ginseng plants. These results suggest that these methods are able to authenticate the concerned Panax species. Broader application of this approach to authenticate other morphologically similar medicinal materials is rationalized.

Effects of ambient air pollution on daily mortality in a cohort of patients with congestive heart failure

This study was planned to test the hypothesis that patients with congestive heart failure are more susceptible to the harmful effects of ambient air pollution than the general population. We used both general additive Poisson regression and the case-crossover approach to test the hypothesis. The effect of air pollution on daily mortality of patients with congestive heart failure among residents of Seoul, South Korea, during the period 1994--1998 was compared with that of the general population in the same area and the same period. The odds ratios and 95% confidence intervals (95% CIs) estimated from general additive models in the general population for an interquartile range increase of particulate matter less than 10 microm in diameter (42.1 microg/m(3)), carbon monoxide (0.59 ppm), nitrogen dioxide (14.6 ppb), sulfur dioxide (9.9 ppb), and ozone (20.5 ppb) were 1.014 (95% CI = 1.006- 1.022), 1.022 (95% CI = 1.017- 1.029), 1.021 (95% CI = 1.014- 1.029), 1.020 (95% CI = 1.012--1.028), and 1.010 (95% CI = 1.002--1.017), respectively. The estimated effects appeared larger among the congestive heart failure patients than among the general population (2.5 approximately 4.1 times higher depending on the pollutants). The results from the case-crossover analysis were similar. The finding of a stronger association in the patients with congestive heart failure reinforces the evidence that a harmful effect of air pollution is mediated by cardiovascular mechanisms.

1,2-bis(2-Aminophenoxy)ethane-N,N,N',N'-tetraacetic acid induces caspase-mediated apoptosis and reactive oxygen species-mediated necrosis in cultured cortical neurons

Sustained alteration in [Ca(2+)]i triggers neuronal death. We examined morphological and signaling events of Ca(2+)-deficiency-induced neuronal death. Cortical cell cultures exposed to 20 microM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM), an intracellular calcium chelator, underwent neuronal apoptosis within 12 h that was evident by shriveled cell bodies, aggregated and condensed nuclear chromatin, and disrupted nuclear membrane. Thereafter, surviving neurons revealed typical necrosis, accompanied by swelling of cell body and mitochondria, over 24 h. Both apoptosis and necrosis were prevented by inclusion of 1 microg/mL cycloheximide, a protein synthesis inhibitor. Treatment with BAPTA-AM induced translocation of Bax into mitochondria within 4 h and release of cytochrome c from mitochondria over 4-12 h. An active fragment of caspase-3, a downstream mediator of cytochrome c, was observed within 8 h and cleaved PHF-1-positive tau. Administration of zVAD-fmk, a broad inhibitor of caspases, or DEVD-amc, a selective inhibitor of caspase-3, selectively prevented the apoptosis component of BAPTA-AM neurotoxicity. In contrast, BAPTA-AM-induced necrosis was propagated through sequential production of superoxide, mitochondrial and cytoplasmic reactive oxygen species. Combined treatment with caspase inhibitors and antioxidants blocked BAPTA-AM neurotoxicity. The present study suggests that neurons deficient in [Ca(2+)]i undergo caspase-3-mediated apoptosis and reactive oxygen species (ROS)-mediated necrosis.

Phosphorylation of purified recombinant hepatitis B virus-X protein by mitogen-activated protein kinase and protein kinase C in vitro

The recombinant human hepatitis B virus-X protein (rhHBx) has been expressed as inclusion bodies in Escherichia coli and purified. By sequential dialysis of urea, rhHBx was folded into the native structure, which was demonstrated by both the efficacy of its transcriptional activation of the adenovirus major late promoter, fluorescence and circular dichroism (CD) analysis. The increase in CD values at 220 nm and a corresponding blue shift of the intrinsic fluorescence emission confirmed the ability of HBx to refold in lower concentrations of urea to produce the active protein. After purification and renaturation, the rhHBx protein was found to be phosphorylated by protein kinase C (PKC) and mitogen-activated protein kinase (MAPK). In vivo phosphorylation of HBx was also demonstrated. Although PKC and MAPK enhance the HBx phosphorylation in vitro, neither protein kinase A nor caseine kinase II (CKII) phosphorylate HBx protein, though there are possible substrate residues of both kinases in HBx protein. Phosphoamino acid analysis of the total acid hydrolyzed HBx showed that serine residues can be phosphorylated by PKC or MAPK.

Observability of quantum phase fluctuations in cuprate superconductors

We study the order parameter phase fluctuation effects in cuprate superconductors near T = 0, using a quasi-two-dimensional d-wave BCS model. An effective phason theory is obtained which is used to estimate the strength of the fluctuations, the fluctuation correction to the in-plane penetration depth, and the pair-field susceptibility. We find that, while the phase fluctuation effects are difficult to observe in the renormalization of the superfluid phase stiffness, they may be observed in a pair tunneling experiment which measures the pair-field susceptibility.

Expression of Th2 cytokines decreases the development of and improves Behçet's disease-like symptoms induced by herpes simplex virus in mice

In the etiology of Behçet's disease (BD), viral infection has long been postulated as a contributing factor, and viral involvement has been demonstrated. However, viral infection alone is not sufficient to explain the pathogenesis of BD, and some evidence suggests that immunologic abnormalities are also important. To study the possible role of immune regulation in the development of BD-like symptoms induced by herpes simplex virus inoculation in ICR mice, macrophages were deleted by use of liposome-encapsulated clodronate (lip-Cl(2)MDP). Treatment with lip-Cl(2)MDP suppressed the development of BD-like symptoms, and this suppression was correlated with the induction of interleukin-4 expression in mouse spleens. When the Th2 adjuvant ovalbumin (OVA)-alum was injected into mice with BD-like symptoms, their cutaneous symptoms improved. Adoptive transfer with splenocytes from OVA-alum-injected mice also resulted in improvement. These findings suggest that up-regulated Th2 cytokine expression can attenuate the development of and improve some BD-like symptoms.

Histone deacetylases induce angiogenesis by negative regulation of tumor suppressor genes

Low oxygen tension influences tumor progression by enhancing angiogenesis; and histone deacetylases (HDAC) are implicated in alteration of chromatin assembly and tumorigenesis. Here we show induction of HDAC under hypoxia and elucidate a role for HDAC in the regulation of hypoxia-induced angiogenesis. Overexpressed wild-type HDAC1 downregulated expression of p53 and von Hippel-Lindau tumor suppressor genes and stimulated angiogenesis of human endothelial cells. A specific HDAC inhibitor, trichostatin A (TSA), upregulated p53 and von Hippel-Lindau expression and downregulated hypoxia-inducible factor-1alpha and vascular endothelial growth factor. TSA also blocked angiogenesis in vitro and in vivo. TSA specifically inhibited hypoxia-induced angiogenesis in the Lewis lung carcinoma model. These results indicate that hypoxia enhances HDAC function and that HDAC is closely involved in angiogenesis through suppression of hypoxia-responsive tumor suppressor genes.

Expression of the Xenopus homologue of the receptor for activated C-kinase 1 (RACK1) in the Xenopus embryo

We have isolated the Xenopus homologue of the receptor for activated C-kinase 1 (RACK1), whose amino acid sequence shows significant similarity with other vertebrate RACK1s. XRACK1 is a maternally expressed gene and its zygotic expression is detected in the antero-dorsal region and dorsal midline in the late neurula. At tailbud stage, rather diffuse staining is seen in the somite and head. Later, XRACK1 mRNA is expressed highly in ventrally migrating abdominal muscle anlagen, where it remains expressed during subsequent stages.

Juxtaglomerular cell tumor of the kidney: a case report

We report a case of renin-secreting juxtaglomerular cell tumor which developed in a hypertensive 47-yr-old Korean man. Presumptive clinical diagnosis was made before surgery based on the high level of plasma renin and the radiologic evidence of renal mass. Grossly, a round, bulging, well-encapsulated mass of 3 x 3 cm was located in the mid-portion of the right kidney. On microscopic examination, the tumor was composed of ovoid to polyhedral cells with bland nuclei, indistinct nucleoli and light eosinophilic cytoplasm. The immunostaining for renin showed strong positivity in the cytoplasm of tumor cells. The characteristic rhomboid shaped renin protogranules were observed in ultrastructural analysis.

SIMPL is a tumor necrosis factor-specific regulator of nuclear factor-kappaB activity

The IL-1 receptor-associated kinase (IRAK/mPLK) is linked to the regulation of nuclear factor-kappaB (NF-kappaB)-dependent gene expression. Here we describe a novel binding partner of IRAK/mPLK that we term SIMPL (signaling molecule that associates with the mouse pelle-like kinase). Overexpression of SIMPL leads to the activation of NF-kappaB-dependent promoters, and inactivation of SIMPL inhibits IRAK/mPLK as well as tumor necrosis factor receptor type I-induced NF-kappaB activity. Dominant inhibitory alleles of IkappaB kinase (IKKalpha or IKKbeta) block the activation of NF-kappaB by IRAK/mPLK and SIMPL. Furthermore, SIMPL binds IRAK/mPLK and the IKKs in vitro and in vivo. In the presence of antisense mRNA to SIMPL, the physical association between IRAK/mPLK and IKKbeta but not IRAK/mPLK and IKKalpha is greatly diminished. Moreover, dominant-negative SIMPL blocks IKKalpha- or IKKbeta-induced NF-kappaB activity. These results lead us to propose a model in which SIMPL functions to regulate NF-kappaB activity by linking IRAK/mPLK to IKKbeta/alpha-containing complexes.

Edge electron states for quasi-one-dimensional organic conductors in the magnetic-field-induced spin-density-wave phases

We develop a microscopic picture of the electron states localized at the edges perpendicular to the chains in the Bechgaard salts in the quantum Hall regime. In a magnetic-field-induced spin-density-wave state characterized by an integer N, there exist N branches of chiral gapless edge excitations. Localization length is much longer and velocity much lower for these states than for the edge states parallel to the chains. We calculate the contribution of these states to the specific heat and propose a time-of-flight experiment to probe the propagating edge modes directly.

Air pollution and daily mortality in seven major cities of Korea, 1991-1997

The relationship between ambient air pollution and daily mortality in seven major cities of Korea for the period 1991-1997 was examined. These cities account for half of the Korean population (about 22 million). The observed concentrations of sulfur dioxide (SO(2), mean=23.3 ppb), ozone (O(3), mean=23.7 ppb), and total suspended particulates (TSP, mean=77.9 microg/m(3)) during the study period were at levels below Korea's current ambient air quality standards. Generalized additive models were applied to allow for the highly flexible fitting of seasonal and long-term time trends in air pollution as well as nonlinear associations with weather variables, such as air temperature and relative humidity. In city-specific analyses, an increase of 50 ppb of SO(2) corresponded to 1-12% more deaths, given constant weather conditions. The risk of all-cause mortality was estimated to increase by 0.5-4%, with an increase in the 2-day moving average of TSP levels equal to 100 microg/m(3). In multipollutant models with pooled data, we found that the estimated risk of death by SO(2) was notably unaffected by adding the other two pollutants (TSP and O(3)) to the model and was statistically significant in various regression models. The rate ratio (RR) for SO(2) remained elevated, indicating an excess mortality of 3% 50 ppb (RR=1.03; 95% CI, 1.01-1.05). TSP's effect on mortality maintained its significance with O(3), but not with SO(2). This implies that there may be collinearity problems where TSP and SO(2) are included in the same model or that TSP may function less than SO(2) as a surrogate for fine particles in the ambient air of Korea. In conclusion, increased mortality was associated with air pollution at SO(2) levels below the current recommendation for air quality. Further research is needed to clarify the relationship between SO(2) and fine particles in Korea.

Identification of the histidine and aspartic acid residues essential for enzymatic activity of a family I.3 lipase by site-directed mutagenesis

A lipase from Pseudomonas sp. MIS38 (PML) is a member of the lipase family I.3. We analyzed the roles of the five histidine residues (His(30), His(274), His(291), His(313), and His(365)) and five acidic amino acid residues (Glu(253), Asp(255), Asp(262), Asp(275), and Asp(290)), which are fully conserved in the amino acid sequences of family I.3 lipases, by site-directed mutagenesis. We showed that the mutation of His(313) or Asp(255) to Ala almost fully inactivated the enzyme, whereas the mutations of other residues to Ala did not seriously affect the enzymatic activity. Measurement of the far- and near-UV circular dichroism spectra suggests that inactivation by the mutation of His(313) or Asp(255) is not due to marked changes in the tertiary structure. We propose that His(313) and Asp(255), together with Ser(207), form a catalytic triad in PML.

Heat shock protein 90 mediates protein-protein interactions between human aminoacyl-tRNA synthetases

Heat shock protein 90 (hsp90) is a molecular chaperone responsible for protein folding and maturation in vivo. Interaction of hsp90 with human glutamyl-prolyl-tRNA synthetase (EPRS) was found by genetic screening, co-immunoprecipitation, and in vitro binding experiments. This interaction was sensitive to the hsp90 inhibitor, geldanamycin, and also ATP, suggesting that the chaperone activity of hsp90 is required for interaction with EPRS. Interaction of EPRS with hsp90 was targeted to the region of three tandem repeats linking the two catalytic domains of EPRS that is also responsible for the interaction with isoleucyl-tRNA synthetase (IRS). Interaction of EPRS and IRS also depended on the activity of hsp90, implying that their association was mediated by hsp90. EPRS and IRS form a macromolecular protein complex with at least six other tRNA synthetases and three cofactors. hsp90 preferentially binds to most of the complex-forming enzymes rather than those that are not found in the complex. In addition, inactivation of hsp90 interfered with the in vivo incorporation of the nascent aminoacyl-tRNA synthetases into the multi-ARS complex. Thus, hsp90 appears to mediate protein-protein interactions of mammalian tRNA synthetases.

NT-4/5 exacerbates free radical-induced neuronal necrosis in vitro and in vivo

Neurotrophins render neurons highly vulnerable to certain injuries. We examined the possibility that NT-4/5 would enhance free radical neurotoxicity in vivo as well as in vitro. Striatal neurons exposed to 10 microM Fe(2+) or 1 mM l-buthionine-[S, R]-sulfoximine (BSO) underwent mild degeneration within 24 h. With concurrent addition of 10-100 ng/ml NT-4/5, neuronal death following exposure to Fe(2+) or BSO was significantly increased and suppressed by addition of 100 microM trolox, an antioxidant. In the adult brain, the intrastriatal injections of 20 nmol Fe(2+) revealed features of neuronal necrosis such as swelling cell body and mitochondria, fenestration of plasma membrane prior to nuclear membrane, and scattering condensation of nuclear chromatin. Cotreatment with 1.8 microg NT-4/5 augmented the striatal damage 24 h following the injections of Fe(2+). This study implies that free radicals produce necrotic degeneration in vivo as well as in vitro that becomes more sensitive in the presence of neurotrophins.

Characterization of AMC-HN-9, a cell line established from an undifferentiated carcinoma of the parotid gland: expression of alpha6beta4 with the absence of BP180 and 230

We recently reported the development of a cell line, AMC-HN-9, established from an undifferentiated carcinoma (UDC) of the parotid gland. AMC-HN-9 consists mostly of spindle-shaped cells, has poor in vitro adhesiveness and an in vitro appearance that is different from that of other epithelial cell lines. To test the hypothesis that structural or functional abnormalities of the hemidesmosomes might contribute to the morphological appearance and biology of UDCs, we studied the expression of hemidesmosomal proteins in AMC-HN-9. Flow cytometry, indirect immunofluorescence, immunoprecipitation, reverse transcriptase-polymerase chain reaction, and cytogenetic analysis were used. AMC-HN-9 cells express the alpha6 and beta4 integrin subunits at nearly the same intensity as head and neck squamous cell carcinoma cell lines. However, AMC-HN-9 does not express BP180 and BP230, although there is no gross deletion of the loci of the BP180 and BP230 genes, suggesting that a more subtle mechanism has silenced these genes. In conclusion, the failure to express certain hemidesmosomal proteins is a likely explanation for the functional and morphologic characteristics of UDC cells both in vivo and in vitro.

Inhibition of NFkappaB by methyl chlorogenate from Eriobotrya japonica

Methylchlorogenic acid (MC) is one of the main components in the leaves of Eriobotrya japonica. We previously reported that MC is the most potent antioxidant among several components of Eriobotrya japonica, and its antioxidant activity is stronger than that of chlorogenic acid. Antioxidants are expected to inhibit redox-sensitive NFkappaB activation since NFkappaB is readily influenced by cellular oxidative state. Based on these findings, in vivo experiments with MC were conducted to determine its ability to downregulate the NFkappaB activation in mouse liver. Results clearly showed that MC is a potent suppressor of BHP-induced NFkappaB activation. We observed a significant reduction by MC on BHP-induced translocation of p65 subunit of NFkappaB. This may be due to formation of p50/p65 heterodimer, which is mainly inducible NFkappaB. MC slightly blocked the BHP-induced IkappaB alpha degradation. There is a possibility of IkappaB alpha resynthesis via activated NFkappaB during a 5 h waiting period following BHP injection. The present results suggest that MC may inhibit NFkappaB activation, exhibiting its ability to downregulate the NFkappaB-dependent gene expression. Thus, it can be expected that MC may have potential for therapeutic intervention on various NFkappaB-dependent pathological conditions such as inflammatory or possibly mutagenic processes.

Crystal structure of the Escherichia coli Rob transcription factor in complex with DNA

The Escherichia coli Rob protein is a transcription factor belonging to the AraC/XylS protein family that regulates genes involved in resistance to antibiotics, organic solvents and heavy metals. The genes encoding these proteins are activated by the homologous proteins MarA and SoxS, although the level of activation can vary for the different transcription factors. Here we report a 2.7 A crystal structure of Rob in complex with the micF promoter that reveals an unusual mode of binding to DNA. The Rob-DNA complex differs from the previously reported structure of MarA bound to the mar promoter, in that only one of Rob's dual helix-turn-helix (HTH) motifs engages the major groove of the binding site. Biochemical studies show that sequence specific interactions involving only one of Rob's HTH motifs are sufficient for high affinity binding to DNA. The two different modes of DNA binding seen in crystal structures of Rob and MarA also match the distinctive patterns of DNA protection by AraC at several sites within the pBAD promoter. These and other findings suggest that gene activation by AraC/XylS transcription factors might involve two alternative modes of binding to DNA in different promoter contexts.

Inactivation of interferon regulatory factor-1 tumor suppressor protein by HPV E7 oncoprotein. Implication for the E7-mediated immune evasion mechanism in cervical carcinogenesis

In studying biological roles of interferon regulatory factor (IRF)-1 tumor suppressor in cervical carcinogenesis, we found that HPV E7 is functionally associated with IRF-1. Binding assays indicate a physical interaction between IRF-1 and HPV E7 in vivo and in vitro. The carboxyl-terminal transactivation domain of IRF-1 was required for the interaction. Transient co-expression of E7 significantly inhibits the IRF-1-mediated activation of IFN-beta promoter in NIH-3T3 cells. Co-transfection of E7 mutants reveals that the pRb-binding portion of E7 is necessary for the E7-mediated inactivation of IRF-1. It was next determined whether histone deacetylase (HDAC) is involved in the inactivation mechanism as recently suggested, where the carboxyl-terminal zinc finger domain of E7 associates with NURD complex containing HDAC. When trichostatin A, an inhibitor of HDAC, was treated, the repressing activity of E7 was released in a dose-dependent manner. Furthermore, the mutation of zinc finger abrogates such activity without effect on the interaction with IRF-1. These results suggest that HPV E7 interferes with the transactivation function of IRF-1 by recruiting HDAC to the promoter. The immune-promoting role of IRF-1 evokes the idea that our novel finding might be important for the elucidation of the E7-mediated immune evading mechanism that is frequently found in cervical cancer.