Mithramycin inhibits SP1 binding and selectively inhibits transcriptional activity of the dihydrofolate reductase gene in vitro and in vivo

The promoter of the human dihydrofolate reductase (DHFR) gene contains two consensus binding sites for the DNA binding protein Sp1. DNAse protection and gel mobility shift assays demonstrate binding of recombinant Sp1 to both decanucleotide Sp1 binding sequences which are located 49 and 14 base pairs upstream of the transcription start site. The more distal of the two binding sites exhibits a somewhat higher affinity for Sp1. The G-C specific DNA binding drug, mithramycin, binds to both consensus sequences and prevents subsequent Sp1 binding. Promoter-dependent in vitro transcription of a DHFR template is selectively inhibited by mithramycin when compared to the human H2b histone gene. A similar effect is also noted in vivo. Mithramycin treatment of MCF-7 human breast carcinoma cells containing an amplified DHFR gene induces selective inhibition of DHFR transcription initiation, resulting in a decline in DHFR mRNA level and enzyme activity. This selective inhibition of DHFR expression suggests that it is possible to modulate the overexpression of the DHFR gene in methotrexate resistant cells.

Hepatitis C virus core protein cooperates with ras and transforms primary rat embryo fibroblasts to tumorigenic phenotype

We have previously demonstrated that hepatitis C virus (HCV) core protein regulates cellular protooncogenes at the transcriptional level; this observation implicates core protein in the alteration of normal hepatocyte growth. In the present study, the transforming potential of the HCV core gene was investigated by using primary rat embryo fibroblast (REF) cells which were transfected with or without cooperative oncogenes. Integration of the HCV core gene resulted in expression of the viral protein in REF stable transformants. REF cells cotransfected with HCV core and H-ras genes became transformed and exhibited rapid proliferation, anchor-independent growth, and tumor formation in athymic nude mice. Results from these studies suggest that the core protein plays an important role in the regulation of HCV-infected cell growth and in the transformation to tumorigenic phenotype. These observations suggest a possible mechanism for this viral protein in the pathogenesis of hepatocellular carcinoma in HCV-infected humans.

BNIP3 heterodimerizes with Bcl-2/Bcl-X(L) and induces cell death independent of a Bcl-2 homology 3 (BH3) domain at both mitochondrial and nonmitochondrial sites

BNIP3 (formerly NIP3) is a pro-apoptotic, mitochondrial protein classified in the Bcl-2 family based on limited sequence homology to the Bcl-2 homology 3 (BH3) domain and COOH-terminal transmembrane (TM) domain. BNIP3 expressed in yeast and mammalian cells interacts with survival promoting proteins Bcl-2, Bcl-X(L), and CED-9. Typically, the BH3 domain of pro-apoptotic Bcl-2 homologues mediates Bcl-2/Bcl-X(L) heterodimerization and confers pro-apoptotic activity. Deletion mapping of BNIP3 excluded its BH3-like domain and identified the NH(2) terminus (residues 1-49) and TM domain as critical for Bcl-2 heterodimerization, and either region was sufficient for Bcl-X(L) interaction. Additionally, the removal of the BH3-like domain in BNIP3 did not diminish its killing activity. The TM domain of BNIP3 is critical for homodimerization, pro-apoptotic function, and mitochondrial targeting. Several TM domain mutants were found to disrupt SDS-resistant BNIP3 homodimerization but did not interfere with its killing activity or mitochondrial localization. Substitution of the BNIP3 TM domain with that of cytochrome b(5) directed protein expression to nonmitochondrial sites and still promoted apoptosis and heterodimerization with Bcl-2 and Bcl-X(L). We propose that BNIP3 represents a subfamily of Bcl-2-related proteins that functions without a typical BH3 domain to regulate apoptosis from both mitochondrial and nonmitochondrial sites by selective Bcl-2/Bcl-X(L) interactions.

The E1B 19K/Bcl-2-binding protein Nip3 is a dimeric mitochondrial protein that activates apoptosis

Nip3 (nineteen kD interacting protein-3) is an E1B 19K and Bcl-2 binding protein of unknown function. Nip3 is detected as both a 60- and 30-kD protein in vivo and in vitro and exhibits strong homologous interaction in a yeast two-hybrid system indicating that it can homodimerize. Nip3 is expressed in mitochondria and a mutant (Nip3(163)) lacking the putative transmembrane domain and COOH terminus does not dimerize or localize to mitochondria. Transient transfection of epitope-tagged Nip3 in Rat-1 fibroblasts and MCF-7 breast carcinoma induces apoptosis within 12 h while cells transfected with the Nip3(163) mutant have a normal phenotype, suggesting that mitochondrial localization is necessary for induction of cell death. Nip3 overexpression increases the sensitivity to apoptosis induced by granzyme B and topoisomerase I and II inhibitors. After transfection, both Nip3 and Nip3(163) protein levels decrease steadily over 48 h indicating that the protein is rapidly degraded and this occurs in the absence of cell death. Bcl-2 overexpression initially delays the onset of apoptosis induced by Nip3 but the resistance is completely overcome in longer periods of incubation. Nip3 protein levels are much higher and persist longer in Bcl-2 expressing cells. In conclusion, Nip3 is an apoptosis-inducing dimeric mitochondrial protein that can overcome Bcl-2 suppression.

Modulation of synapse formation by cyclic adenosine monophosphate

Synapses between neuroblastoma-hybrid cells and myotubes exhibit a high degree of plasticity. Increase of cyclic adenosine monophosphate (AMP) levels of the hybrid cells for several days results in the appearance of functional voltage-sensitive Ca2+ channels, which are required for evoked secretion of acetylcholine. The results show that cyclic AMP regulates synaptogenesis by regulating the expression of voltage-sensitive Ca2+ channels, and suggest that cyclic AMP affects posttranslational modifications of some glycoproteins and cellular levels of certain proteins.

Factors influencing survival after out-of-hospital cardiac arrest

Survival to hospital discharge was related to the clinical history and emergency care system factors in 285 patients with witnessed cardiac arrest due to ventricular fibrillation. Only the emergency care factors were associated with differences in outcome. Both the period from collapse until initiation of basic life support and the duration of basic life support before delivery of the first defibrillatory shock were shorter in patients who survived compared with those who died (3.6 +/- 2.5 versus 6.1 +/- 3.3 minutes and 4.3 +/- 3.3 versus 7.3 +/- 4.2 minutes; p less than 0.05). A linear regression model based on emergency response times for 942 patients discovered in ventricular fibrillation was used to estimate expected survival rates if the first-responding rescuers, in addition to paramedics, had been equipped and trained to defibrillate. Expected survival rates were higher with early defibrillation (38 +/- 3%; 95% confidence limits) than the observed rate (28 +/- 3%). Because outcome from cardiac arrest is primarily influenced by delays in providing cardiopulmonary resuscitation and defibrillation, factors affecting response time should be carefully examined by all emergency care systems.

A radiation hybrid map of the zebrafish genome

Recent large-scale mutagenesis screens have made the zebrafish the first vertebrate organism to allow a forward genetic approach to the discovery of developmental control genes. Mutations can be cloned positionally, or placed on a simple sequence length polymorphism (SSLP) map to match them with mapped candidate genes and expressed sequence tags (ESTs). To facilitate the mapping of candidate genes and to increase the density of markers available for positional cloning, we have created a radiation hybrid (RH) map of the zebrafish genome. This technique is based on somatic cell hybrid lines produced by fusion of lethally irradiated cells of the species of interest with a rodent cell line. Random fragments of the donor chromosomes are integrated into recipient chromosomes or retained as separate minichromosomes. The radiation-induced breakpoints can be used for mapping in a manner analogous to genetic mapping, but at higher resolution and without a need for polymorphism. Genome-wide maps exist for the human, based on three RH panels of different resolutions, as well as for the dog, rat and mouse. For our map of the zebrafish genome, we used an existing RH panel and 1,451 sequence tagged site (STS) markers, including SSLPs, cloned candidate genes and ESTs. Of these, 1,275 (87.9%) have significant linkage to at least one other marker. The fraction of ESTs with significant linkage, which can be used as an estimate of map coverage, is 81.9%. We found the average marker retention frequency to be 18.4%. One cR3000 is equivalent to 61 kb, resulting in a potential resolution of approximately 350 kb.

Cubilin dysfunction causes abnormal metabolism of the steroid hormone 25(OH) vitamin D(3)

Steroid hormones are central regulators of a variety of biological processes. According to the free hormone hypothesis, steroids enter target cells by passive diffusion. However, recently we demonstrated that 25(OH) vitamin D(3) complexed to its plasma carrier, the vitamin D-binding protein, enters renal proximal tubules by receptor-mediated endocytosis. Knockout mice lacking the endocytic receptor megalin lose 25(OH) vitamin D(3) in the urine and develop bone disease. Here, we report that cubilin, a membrane-associated protein colocalizing with megalin, facilitates the endocytic process by sequestering steroid-carrier complexes on the cellular surface before megalin-mediated internalization of the cubilin-bound ligand. Dogs with an inherited disorder affecting cubilin biosynthesis exhibit abnormal vitamin D metabolism. Similarly, human patients with mutations causing cubilin dysfunction exhibit urinary excretion of 25(OH) vitamin D(3). This observation identifies spontaneous mutations in an endocytic receptor pathway affecting cellular uptake and metabolism of a steroid hormone.

Transcriptional repression of p53 promoter by hepatitis C virus core protein

Our previous results have suggested that the putative core protein of hepatitis C virus (HCV) transcriptionally regulates cellular and viral genes, inhibits cisplatin and c-myc-mediated apoptotic cell death under certain conditions, and transforms primary rat embryo fibroblast cells with a cooperative oncogene. Because HCV appears to cause hepatocellular carcinoma, we evaluated the regulatory role of the HCV core protein on p53, a well known tumor suppressor gene, by an in vitro transfection assay. HCV core protein repressed transcriptional activity of the p53 promoter when tested separately in COS7 and HeLa cells. Deletion mutational analysis of the HCV core gene indicated that the regulatory domain involved in the repression of p53 transcriptional activity is located around amino acid residues 80-122 encompassing a putative DNA binding motif and two major phosphorylation sites. Results from this study suggest that the putative core protein may have an important biological role in the promotion of cell growth by repressing p53 transcription, and this appears to be consistent with certain earlier observations about HCV core moving into the nucleus.

Hepatitis C virus NS5A physically associates with p53 and regulates p21/waf1 gene expression in a p53-dependent manner

We have previously demonstrated that hepatitis C virus (HCV) NS5A protein promotes cell growth and transcriptionally regulates the p21/waf1 promoter, a downstream effector gene of p53. In this study, we investigated the molecular mechanism of NS5A-mediated transcriptional repression of p21/waf1. We observed that transcriptional repression of the p21/waf1 gene by NS5A is p53 dependent by using p53 wild-type (+/+) and null (-/-) cells. Interestingly, p53-mediated transcriptional activation from a synthetic promoter containing multiple p53 binding sites (PG13-LUC) was abrogated following expression of HCV NS5A. Additional studies using pull-down experiments, in vivo coimmunoprecipitation, and mammalian two-hybrid assays demonstrated that NS5A physically associates with p53. Confocal microscopy revealed sequestration of p53 in the perinuclear membrane and colocalization with NS5A in transfected HepG2 and Saos-2 cells. Together these results suggest that an association of NS5A and p53 allows transcriptional modulation of the p21/waf1 gene and may contribute to HCV-mediated pathogenesis.

Transcriptional regulation of cellular and viral promoters by the hepatitis C virus core protein

The genomic region encoding the hepatitis C virus (HCV) core protein was cloned into a mammalian expression vector to study its role on the transcriptional regulation of cellular proto-oncogene and viral promoters. Using a transient transfection assay in human hepatocellular carcinoma (HepG2) cells, we demonstrate that the HCV core protein activates the human c-myc, Rous sarcoma virus long terminal repeat (LTR), and simian virus 40 (SV40) early promoters; and suppresses the c-fos promoter and human immunodeficiency virus type 1 (HIV-1) LTR activity. The transcriptional regulation of cellular proto-oncogenes by the HCV core protein suggests possible involvement of the core protein in the deregulation of normal hepatocyte growth and hepatocarcinogenesis.

Suppression of apoptotic cell death by hepatitis C virus core protein

We have previously demonstrated the role of hepatitis C virus (HCV) core protein in the transcriptional regulation of cellular and unrelated viral promoters. Furthermore, the core protein in cooperation with H-ras oncogene transforms primary rat embryo fibroblast cells to the tumorigenic phenotype. In the present study, the functional role of HCV core protein was investigated to determine its potential to inhibit the onset of apoptotic cell death. Expression of HCV core protein inhibited cisplatin mediated apoptosis in human cervical epithelial cells, and apoptosis induced by the overexpression of c-myc in Chinese hamster ovarian cells. Results from these studies suggest that the core protein may have a biological implication in the pathogenesis of HCV infection.

Considerations for improving survival from out-of-hospital cardiac arrest

Since the implementation of a paramedic system in Seattle, yearly survival rates from out-of-hospital cardiac arrest due to ventricular fibrillation have averaged 25% without any significant increase over the years. Outcome for cardiac arrest associated with other rhythms has been poor: when asystole was the first rhythm recorded, only 1% of patients survived; when electromechanical dissociation was initially present, only 6% survived. For cases of electromechanical dissociation, neither the type of rhythm nor the rate appear to influence outcome. Survival from ventricular fibrillation can be improved by shortening the delay to initiation of CPR and to defibrillation. When outcome in 244 witnessed arrests was related to the times to beginning CPR and to initial defibrillation, mortality increased 3% each minute until CPR was begun and 4% a minute until the first shock was delivered. New strategies that minimize delays appear to have the greatest promise for improving survival after cardiac arrest.

Target cell metabolism of 1,25-dihydroxyvitamin D3 to calcitroic acid. Evidence for a pathway in kidney and bone involving 24-oxidation

1,25-dihydroxyvitamin D3 is converted to calcitroic acid before being excreted in the bile. Biosynthesis of calcitroic acid has been demonstrated in two target cells of vitamin D, in the kidney and the osteoblastic cell line UMR-106. Calcitroic acid was identified by combinations of h.p.l.c., u.v. spectroscopy and mass spectrometry. Evidence is presented that calcitroate is derived from the 24-oxidation pathway, possibly through the intermediate 24,25,26,27-tetranor-1,23-dihydroxyvitamin D3. The 24-oxidation pathway to calcitroic acid in bone cells is stimulated by 1,25-dihydroxyvitamin D3. The pathway in both bone cells and perfused kidney operates at physiological concentrations of substrate and appears to be capable of rapid clearance of the hormone.

Amplitude of ventricular fibrillation waveform and outcome after cardiac arrest

The amplitude of ventricular fibrillation found initially in 394 patients was compared to clinical and logistical findings at the time of cardiac arrest. Peak-to-peak amplitude averaged 0.55 +/- 0.25 mV; a very low amplitude (0.2 mV or less) or "fine" fibrillation was present in 66 patients (17%). The amplitude was not found to be related to clinical histories, but depended on the length of the period from collapse until start of basic life support (p = 0.004) and the delay until assessment by paramedics (p = 0.001). Survival rates were strongly associated with amplitude: only 4 patients (6%) with fine ventricular fibrillation survived, compared to 117 or 328 patients (36%) in whom the initial amplitude was higher (p less than 0.001). Patient outcome related to amplitude even after adjusting for clinical history and logistical delays (p less than 0.005). We conclude that fine ventricular fibrillation is in part the result of delay in initiation of treatment, and that fibrillation amplitude is a powerful indicator of outcome after cardiac arrest.

Inhibition of tumor necrosis factor (TNF-alpha)-mediated apoptosis by hepatitis C virus core protein

Hepatitis C virus (HCV) putative core protein has displayed many intriguing biological properties. Since tumor necrosis factor (TNF) plays an important role in controlling viral infection, in this study the effect of the core protein was investigated on the TNF-alpha induced apoptosis of human breast carcinoma cells (MCF7). HCV core protein when expressed inhibited TNF-alpha-induced apoptotic cell death unlike the control MCF7 cells, as determined by cell viability and DNA fragmentation analysis. Additionally, HCV core protein blocked the TNF-induced proteolytic cleavage of the death substrate poly(ADP-ribose) polymerase from its native 116-kDa protein to the characteristic 85-kDa polypeptide. Results from this study suggest that the HCV core protein plays a role in the inhibition of TNF-alpha-mediated cell death. Thus, the ability of core protein to inhibit the TNF-mediated apoptotic signaling pathway may provide a selective advantage for HCV replication, allowing for evasion of host antiviral defense mechanisms.

Randomized trial of breast self-examination in Shanghai: methodology and preliminary results

BACKGROUND

The efficacy of breast self-examination in helping to reduce mortality from breast cancer has not been rigorously demonstrated.

PURPOSE

To assess efficacy, a large, randomized trial was initiated in Shanghai, China.

METHODS

From October 1989 to October 1991, 267040 current and retired female employees associated with 520 factories in the Shanghai Textile Industry Bureau were randomly assigned on the basis of factory to either a self-examination instruction group (133375 women) or a control group (133665 women). The women were born within the period from 1925 through 1958. Women in the instruction group were given intensive training in breast self-examination, including the use of silicone breast models and personalized instruction, plus two subsequent reinforcement sessions and multiple reminders to practice the technique. Women in the control group were asked to attend training sessions on the prevention of low back pain. All women have been followed for the development of breast diseases and for death from breast cancer.

RESULTS

A high level of participation during the first 4-5 years of the trial was documented among women in the instruction group. Randomly sampled women in this group demonstrated greater proficiency in detecting lumps in breast models than did randomly sampled women in the control group. Approximately equal numbers of breast cancers were detected in the two groups (331 in the instruction group and 322 in the control group) through 1994, which is the last year for which case-finding efforts have been completed. The breast cancers detected in the instruction group were not diagnosed at an appreciably earlier stage or smaller size than those in the control group. More benign breast lesions were detected in the instruction group than in the control group (1457 versus 623, respectively), suggesting a higher index of suspicion for women who received training. Cumulative breast cancer mortality rates through 5 years from entry into the study were nearly equivalent for the two groups.

CONCLUSIONS

Breast self-examination has not led to a reduction in mortality from breast cancer in this study cohort in the first several years since the trial began. A shift toward the diagnosis of disease at a less advanced stage in women given instruction has also not been demonstrated. Longer follow-up of participants in this trial is required before final assessment can be made of the efficacy of breast self-examination.

IMPLICATIONS

At this time, there is insufficient evidence to recommend for or against the teaching of breast self-examination.

Improved neurologic recovery and survival after early defibrillation

Eighty-seven patients who had out-of-hospital cardiac arrests received defibrillating shocks delivered by minimally trained first responders before the arrival of paramedics in a city with short emergency response times. Their outcomes were compared with those of 370 other victims who received only basic life support by first responders until paramedics arrived. Survival was improved by early defibrillation in cases in which there was a delay in initiating cardiopulmonary resuscitation and in which paramedic response times exceeded 9 min; there was 62% survival after early defibrillation by first responders and 27% if first responders provided only basic life support (p less than .02). Neurologic recovery was also improved after early defibrillation. Eighteen of 46 resuscitated patients (39%) receiving early defibrillation were awake at 24 hr compared with 49 of 204 patients (24%) who received only basic life support while awaiting paramedics (p less than .02). Incorporating defibrillation as part of basic life support can reduce both mortality and morbidity from cardiac arrest, even in cities with established, rapidly responding emergency care systems.

Functional interactions between the fusion protein and hemagglutinin-neuraminidase of human parainfluenza viruses

The fusion glycoprotein (F) and hemagglutinin-neuraminidase (HN) genes of human parainfluenza virus type 2 (PI2) were molecularly cloned and expressed in HeLa-T4 cells by using the vaccinia virus-T7 transient expression system. Expression of the F and HN proteins was detected by using immunoprecipitation and surface immunofluorescence staining. Although the F protein was found to be cleaved into F1 and F2 and expressed on cell surfaces, no cell fusion was observed. However, cotransfection of the F-protein gene together with the P12 HN gene resulted in significant levels of cell fusion. Cell fusion was also observed when separate cell cultures were transfected with the HN and F genes and the F-expressing cells were mixed with the HN-expressing cells. Surprisingly, when the PI2 F protein was expressed together with the parainfluenza virus type 3 (PI3) HN protein, no fusion was detectable in the transfected cells. Similarly, no fusion was found upon coexpression of the PI2 HN and PI3 F proteins. However, coexpression of the PI3 F and HN proteins resulted in extensive cell fusion, which resembled the PI2 coexpression result. These results indicate that under the conditions used, the F protein is unable to cause fusion by itself and the HN protein provides a specific function in cell fusion which cannot be provided by another paramyxovirus attachment protein. Further, the results suggest that a type-specific functional interaction between the F and HN proteins is involved in mediating cell fusion.

Hepatitis C virus NS5A protein modulates cell cycle regulatory genes and promotes cell growth

The phosphoprotein NS5A of hepatitis C virus has recently been suggested to control PKR protein kinase for resistance to interferon. To investigate other functions of NS5A, studies were initiated on the regulation of transcription of important cellular genes and of cell growth by this protein. The results suggested that NS5A protein represses transcription of the cell cycle regulatory gene p21WAF1, while it activates the human proliferating cell nuclear antigen gene in murine fibroblasts and human hepatoma cells. Furthermore, introduction of NS5A into murine fibroblasts (NIH3T3) promoted anchorage-independent growth and tumour formation in nude mice. Thus, NS5A appears to exhibit a role in cell growth regulation.

Hepatitis C virus core protein promotes immortalization of primary human hepatocytes

Hepatitis C virus (HCV) core protein has many intriguing properties as a viral factor and is implicated in cell growth regulation. In this study, the cell growth regulation potential of HCV core protein was investigated by introduction of the core genomic region into primary human hepatocytes, a natural host for virus replication and tropism. Core-transfected primary human hepatocytes displayed altered cell morphology resembling that of low-differentiated epithelial cells. Those cells retained an immortalized phenotype and exhibited continuous growth after more than 50 passages over 2 years. Stable hepatocyte transfectants exhibited albumin secretion and HCV core protein expression. Telomerase activity, a characteristic of immortalized or transformed cells, was evident in the transfected hepatocytes immediately after senescence. Anchorage-independent growth of the immortalized hepatocytes provided further evidence for a transformed phenotype. Results from these studies suggest that the HCV core protein promotes primary human hepatocytes to an immortalized phenotype, which may predispose cells over an extended period of time to undergo a transforming event. Thus, HCV core protein appears to contribute to virus-mediated pathogenesis in a persistently infected host.

Smoking as a risk factor for recurrence of sudden cardiac arrest

We obtained information about cessation of smoking in 310 survivors of out-of-hospital cardiac arrest who had been habitual cigarette smokers at the time of their arrest. Patients with coronary heart disease were stratified according to mortality risk on the basis of recognized criteria. The expected first-year rate of recurrent arrest ranged from 2 to 40 percent among the strata. Life-table analyses showed that reformed smokers had a lower incidence of recurrent arrest than patients who continued to smoke (19 vs. 27 percent at three years; P = 0.038 by one-sided test adjusted across strata). This effect occurred to varying degrees in all but the highest risk stratum. No differences in survival were observed for mortality due to other causes. It is possible that continued smoking in these patients led to acceleration of an ongoing atherosclerotic process, but the differences in early survival suggest that smoking may also act in the short term to enhance vulnerability to cardiac arrest.

Hepatitis C virus core protein represses p21WAF1/Cip1/Sid1 promoter activity

Hepatitis C virus (HCV) often causes a prolonged and persistent infection, and an association between hepatocellular carcinoma (HCC) and HCV infection has been noted. Recent experimental evidence using a cloned genomic region suggests that the putative core protein of HCV has numerous biological properties and is implicated as a viral factor for HCV mediated pathogenesis. WAF1/Cip1/Sid1 (p21) is the prototype of a family of proteins that inhibit cyclin-dependent kinases (CDK) and regulate cell cycle progression in eukaryotic cells. In this study, we have observed that the HCV core protein represses the transcriptional activity of the p21 promoter when tested separately by an in-vitro transient expression assay using murine fibroblasts (NIH3T3), human hepatocellular carcinoma (HepG2), and human cervical carcinoma (HeLa) cells. A deletion analysis of the p21 promoter suggested that the HCV core responsive region is located downstream of the p53 binding site. A gel mobility shift analysis showed that the HCV core protein does not bind directly to p21 regulatory sequences. Thus, the HCV core protein appears to act as an effector in the promotion of cell growth by repressing p21 transcription through unknown cellular factor(s).

The receptor for advanced glycation end products (RAGE) specifically recognizes methylglyoxal-derived AGEs

Diabetes-induced hyperglycemia increases the extracellular concentration of methylglyoxal. Methylglyoxal-derived hydroimidazolones (MG-H) form advanced glycation end products (AGEs) that accumulate in the serum of diabetic patients. The binding of hydroimidozolones to the receptor for AGEs (RAGE) results in long-term complications of diabetes typified by vascular and neuronal injury. Here we show that binding of methylglyoxal-modified albumin to RAGE results in signal transduction. Chemically synthesized peptides containing hydroimidozolones bind specifically to the V domain of RAGE with nanomolar affinity. The solution structure of an MG-H1-V domain complex revealed that the hydroimidazolone moiety forms multiple contacts with a positively charged surface on the V domain. The high affinity and specificity of hydroimidozolones binding to the V domain of RAGE suggest that they are the primary AGE structures that give rise to AGEs-RAGE pathologies.

Ectopic expression of hepatitis C virus core protein differentially regulates nuclear transcription factors

The putative core protein of hepatitis C virus (HCV) regulates cellular growth and a number of cellular promoters. To further understand its effect, we investigated the role of the core protein in the endogenous regulation of two distinct transcription factors, nuclear factor-kappaB (NF-kappaB) and activating protein-1 (AP-1), and the related mitogen-activated protein kinase kinase (MAPKK) and c-Jun N-terminal kinase (JNK). Stable cell transfectants expressing the HCV core protein suppressed tumor necrosis factor (TNF)-induced NF-kappaB activation. Supershift analysis revealed that NF-kappaB consists of p50 and p65 subunits. This correlated with inhibition of the degradation of IkappaBalpha, the inhibitory subunit of NF-kappaB. The effect was not specific to TNF, as suppression in core protein-expressing cells was also observed in response to a number of other inflammatory agents known to activate NF-kappaB. In contrast to the effect on NF-kappaB, the HCV core protein constitutively activated AP-1, which correlated with the activation of JNK and MAPKK, which are known to regulate AP-1. These observations indicated that the core protein targets transcription factors known to be involved in the regulation of inflammatory responses and the immune system.