Protein Arginine Methyltransferase 5 Contributes to Paclitaxel-Induced Neuropathic Pain by Activating Transient Receptor Potential Vanilloid 1 Epigenetic Modification in Dorsal Root Ganglion

BACKGROUND

Paclitaxel (PTX), which is a first-line chemotherapy drug used to treat various types of cancers, exhibits peripheral neuropathy as a common side effect that is difficult to treat. Protein arginine methyltransferase 5 (PRMT 5) is a key regulator of the chemotherapy response, as chemotherapy drugs induce PRMT5 expression. However, little is known about the PRMT5-mediated epigenetic mechanisms involved in PTX-induced neuropathic allodynia.

METHODS

Sprague-Dawley rats were intraperitoneally given PTX to induce neuropathic pain. Biochemical analyses were conducted to measure the protein expression levels in the dorsal root ganglion (DRG) of the animals. The von Frey test and hot plate test were used to evaluate nociceptive behaviors.

RESULTS

PTX increased the PRMT5 (mean difference [MD]: 0.68, 95% confidence interval [CI], 0.88-0.48; P < .001 for vehicle)-mediated deposition of histone H3R2 dimethyl symmetric (H3R2me2s) at the transient receptor potential vanilloid 1 ( Trpv1 ) promoter in the DRG. PRMT5-induced H3R2me2s recruited WD repeat domain 5 (WDR5) to increase trimethylation of lysine 4 on histone H3 (H3K4me3) at Trpv1 promoters, thus resulting in TRPV1 transcriptional activation (MD: 0.65, 95% CI, 0.82-0.49; P < .001 for vehicle) in DRG in PTX-induced neuropathic pain. Moreover, PTX increased the activity of NADPH oxidase 4 (NOX4) (MD: 0.66, 95% CI, 0.81-0.51; P < .001 for vehicle), PRMT5-induced H3R2me2s, and WDR5-mediated H3K4me3 in the DRG in PTX-induced neuropathic pain. Pharmacological antagonism and the selective knockdown of PRMT5 in DRG neurons completely blocked PRMT5-mediated H3R2me2s, WDR5-mediated H3K4me3, or TRPV1 expression and neuropathic pain development after PTX injection. Remarkably, NOX4 inhibition not only attenuated allodynia behavior and reversed the above-mentioned signaling but also reversed NOX4 upregulation via PTX.

CONCLUSIONS

Thus, the NOX4/PRMT5-associated epigenetic mechanism in DRG has a dominant function in the transcriptional activation of TRPV1 in PTX-induced neuropathic pain.

[Long-term prognosis of primary focal segmental glomerulosclerosis in children]

Objective: To investigate risk factors for the long-term prognosis of primary focal segmental glomerulosclerosis (FSGS) and associated with renal prognosis in children. Methods: A retrospective study was conducted by collecting clinical data including general information, clinical features and renal pathological findings of 124 children with primary FSGS in Department of Pediatrics of Jinling Hospital from January 2003 to December 2019. The cumulative renal survival rate was calculated by Kaplan-Meier survival analysis. The risk factors related to renal prognosis were identified by Cox regression risk model analysis and receiver operating characteristic (ROC) curve. Results: Among 124 children, 94 were males (75.8%) and 30 were females (24.2%). The children were 16 (14, 17) years of age at the time of kidney biopsies. There were 102 cases (82.3%) aged from 13 to 18 years. The period of follow-up was 64.8 (32.1, 86.0) months. There were 49 cases (39.5%) with nonspecific variant, 33 cases (26.6%) with tip variant, 22 cases (17.7%) with collapsing variant, 14 cases (11.3%) with cellular variant and 6 cases (4.8%) with periportal variant. The data of Kaplan-Meier survival analysis showed that cumulative renal survival rates of end-stage kidney disease (ESKD) or ≥50% decline in estimated glomerular filtration rate (eGFR) from baseline at the year of 5, 10 and 15 after renal biopsies were 66.9%, 51.4% and 21.0% respectively. Multivariate Cox regression analysis showed that hypertension, glomerular segmental sclerosis ratio, moderate to severe chronic tubulointerstitial lesions were independent risk factors for progressing to ESKD or ≥50% reduction in eGFR from baseline in pediatric FSGS (HR=5.28, 1.03, 7.81, 95%CI 2.77-10.05, 1.01-1.04, 4.08-14.98, all P<0.01). ROC curve analysis showed glomerular segmental sclerosis ratio (AUC=0.734, P<0.05, optimal cut-off value=25.4%, sensitivity=50.0%, specificity=88.6%), moderate and severe chronic renal tubulointerstitial lesions (AUC=0.724, P<0.05, sensitivity=46.3%, specificity=98.6%) had good efficacy in evaluating renal outcomes of FSGS. Conclusions: The long-term prognosis of FSGS in children is poor. The risk factors of poor prognosis in children with FSGS are hypertension, moderate to severe chronic renal tubulointerstitial lesions and glomerular segmental sclerosis (≥25.4%).

[Application of dysphonia severity index in laryngeal reflux related voice diseases]

Objective:To discuss the validity and reliability of dysphonia severity index in evaluating the effect of diagnosis and treatment of laryngeal reflux related voice diseases. Method:54 cases of voice disease patients accompanied by laryngopharyngeal reflux from January 2016 to June 2017 in department of otorhinolaryngology of our hospital were divided into two groups according to treatment type. 32 cases in the operation group received laser surgery and standard acid suppression therapy for 6 weeks, and 22 patients in the non-operation group received standard acid suppression therapy for 6 weeks. 24 h multichannel impedance pH (MCII-pH) monitoring was carried out. The indexes of reflux symptom, reflux finding score, subjective auditory perception and objective acoustic parameters of voice were measured before and after treatment, and the dysphonia severity index was calculated and analyzed. Result:There was no significant difference in age, sex and course of disease between the two groups (P> 0.05).Compared with pre-treatment, RSI, RFS, Jitter, Shimmer, G and R in two groups decreased significantly after treatment, and MPT, DSI increased significantly (P<0.05). Before treatment, RSI, RFS, Jitter, Shimmer, G and R in the operation group were significantly higher than those in the non-operation group, and MPT, DSI were lower (P<0.05). There were no significant differences in the parameters between the two groups after treatment (P> 0.05). DSI was negatively correlated with GRBAS scoring parameters, Jitter and Shimmer, and positively correlated with RSI, RFS, and MPT (P<0.01). DSI is related to the location of the lesion (P<0.05) The incidence of anxiety was 27.27% in patients with moderate and severe sudden sensorineural hearing loss, and the incidence of depression was 25.25%. The scores of anxiety and depression were statistically significant (P<0.05). The multivariate logistic regression analysis showed that the status of anxiety and depression was accompanied by symptoms and other diseases (P<0.05). There was a significant difference between the effective group, the significant efficacy group and the cured group (P<0.05). The difference between the scores before and after treatment was compared. Differences in the ineffective group compared with the other three groups, and the cured group compared with the other three groups of anxiety, depression were statistically significant. Conclusion:DSI can be used as an objective evaluation index for the diagnosis and treatment of laryngeal reflux related voice diseases, and it is accurate and reliable.

Ryanodine receptor genes of the rice stem borer, Chilo suppressalis: Molecular cloning, alternative splicing and expression profiling

The ryanodine receptor (RyR) of the calcium release channel is the main target of anthranilic and phthalic diamide insecticides which have high selective insecticidal activity relative to mammalian toxicity. In this study, the full-length cDNA of Chilo suppressalis RyR (CsRyR) was isolated and characterized. The CsRyR mRNA has an open reading frame (ORF) of 15,387bp nucleotides, which encodes 5128 amino acids with GenBank ID: KR088972. Comparison of protein sequences showed that CsRyR shared high identities with other insects of 77-96% and lower identity to mammals and nematodes with only 42-45%. One alternative splicing site (KENLG) unique to Lepidoptera was found and two exclusive exons of CsRyR (I /II) were revealed. Spatial and temporal expression of CsRyR mRNA was at the highest relative level in 3rd instar larvae and head (including brain and muscle), and at the lowest expression level in egg and fat body. The expression levels of whole body CsRyR mRNA were increased remarkably after injection of 4th instar larvae with chlorantraniliprole at 0.004 to 0.4μg/g. This structural and functional information on CsRyR provides the basis for further understanding the selective action of chlorantraniliprole and possibly other diamide insecticides.

Expression and clinical significance of antinuclear antibody in hepatitis C virus infection

BACKGROUND

The prevalence of antinuclear antibody (ANA) has been documented in patients with hepatitis C virus (HCV) infection. We attempted to determine the titer and to characterize the patterns and clinical significance of ANA in HCV infection.

STUDY

Forty-eight consecutive patients with positive anti-HCV antibody and positive HCV RNA were included in this study. Sera from patients were tested for ANA and anti-smooth muscle antibody by indirect immunofluorescence. Serum aminotransferase, alkaline phosphatase, alpha-fetoprotein, and cryoglobulin levels also were determined.

RESULTS

Eleven (23%) of 48 HCV-infected patients were positive for ANA. Antinuclear antibody revealed speckled pattern in 10 (91%) of the 11 ANA-positive HCV-infected patients. Twenty (54%) of 37 ANA-negative HCV-infected patients had detectable pattern with equivocal titer (titer <1.5). The ANA pattern was speckled in all 20 patients. Hepatitis C virus-infected patients with positive ANA were older than the HCV-infected patients with negative ANA (62.90 +/- 11.05 years vs. 56.46 +/- 14.94 years, respectively; p < 0.1). Serum levels of aspartate aminotransferase (39.36 +/- 14.98 IU/L vs. 30.70 +/- 23.15 IU/L, p < 0.05), alkaline phosphatase (189.00 +/- 75.63 IU/L vs. 122.41 +/- 40.88 IU/L, p < 0.01), and alpha-fetoprotein (47.72 +/- 80.47 pg/dL vs. 7.00 +/- 8.28 pg/dL, p < 0.01) were higher in ANA-positive HCV-infected patients than in ANA-negative HCV-infected patients, respectively. There were no significant differences in gender, alanine aminotransferase, anti-smooth muscle antibody, or cryoglobulin between the two groups.

CONCLUSIONS

Antinuclear antibody was present in 11 (23%) of 48 patients with HCV infection in our study. Speckled pattern is the major expression pattern of ANA in HCV infection. Antinuclear antibody-positive HCV-infected patients have significantly higher serum aspartate aminotransferase, alkaline phosphatase, and alpha-fetoprotein levels than ANA-negative HCV-infected patients.

Snakebite complicated with Vibrio vulnificus infection

Snakebite may be complicated with bacteria infections, most of which are Gram-negative bacillus. Snakebite complicated with Vibrio vulnificus infection has not been reported previously. Vibrio vulnificus infection is characterized by a necrotizing wound infection similar to the local lesion of severe snakebite. In Vibrio infections, aggressive debridement with the administration of strong antibiotics as early as possible is the only effective treatment. We report a 79-y-o man who suffered from snakebite on the right palm with rapid progression of hemorrhagic bulla, necrotizing fasciitis, compartment syndrome, and septic shock. Vibrio vulnificuswas cultured from necrotic tissue after aggressive debridement and fasciotomy. The patient recovered from antibiotic treatment and several courses of reconstruction surgery. Severe bacteria infection, such as caused by Vibrio vulnificus, should be considered in snakebite cases refractory to antivenin dosage.

Serological and Molecular Characterization of Peanut chlorotic fan-spot virus, a New Species of the Genus Tospovirus

ABSTRACT To clarify the serological relationship of Peanut chlorotic fan-spot virus (PCFV) with other tospoviruses, antisera were produced against the nucleocapsid (N) proteins of this virus and tospoviruses from four serogroups including Tomato spotted wilt virus (TSWV), Impatiens necrotic spot virus (INSV), Groundnut ringspot virus (GRSV), and Watermelon silver mottle virus (WSMoV). In immunodiffusion tests, the antisera only reacted with their homologous antigens. Similar results were noticed in indirect enzyme-linked immunosorbent assay and immunoblot tests, with the exception that strong cross-reactions were observed in heterologous combinations between TSWV and GRSV. The results indicated that the N protein of PCFV is not serologically related to those of the tospoviruses from the four serogroups. To further characterize the virus, viral S double-stranded RNA was extracted from PCFV-infected Chenopodium quinoa and used for cDNA cloning and sequencing. The full-length viral strand of the S RNA was determined to be 2,833 nucleotides, with an inverted repeat at the 5' and 3' ends and two open reading frames in an ambisense arrangement. The 3'-terminal sequence (5'-AUUGCUCU-3') of the viral S RNA is identical to those of other tospoviruses, indicating that PCFV belongs to the genus Tospovirus. The N and the NSs proteins of PCFV share low amino acid identities (22.3 to 67.5% and 19.3 to 54.2%) with those of reported tospoviruses, respectively. The phylogenetic dendrogram of the N gene of PCFV compared with those of other tospoviruses indicates that PCFV is distinct from other tospoviruses. In hybridization analyses, an N gene cDNA probe of PCFV did not react with viral RNAs of TSWV, GRSV, INSV, and WSMoV, and vice versa. Thus, based on these results, we conclude that PCFV is a new tospovirus species.

AMF1 (GPS2) modulates p53 transactivation

We have reported that the papillomavirus E2 protein binds the nuclear factor AMF1 (also called G-protein pathway suppressor 2 or GPS2) and that their interaction is necessary for transcriptional activation by E2. It has also been shown that AMF1 can influence the activity of cellular transcription factors. These observations led us to test whether AMF1 regulates the functions of p53, a critical transcriptional activator that integrates stress signals and regulates cell cycle and programmed cell death. We report that AMF1 associates with p53 in vivo and in vitro and facilitates the p53 response by augmenting p53-dependent transcription. Overexpression of AMF1 in U2OS cells increases basal level p21(WAF1/CIP1) expression and causes a G(1) arrest. U2OS cells stably overexpressing AMF1 show increased apoptosis upon exposure to UV irradiation. These data demonstrate that AMF1 modulates p53 activities.

Hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome with acute cortical blindness

The coincidence of hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome and cortical blindness is an uncommon but very dramatic event. We describe a case of HELLP syndrome complicating with acute cortical blindness before delivery. A 27 year-old woman, gravida 1, para 0, with normal medical history, was referred to our emergency department at the 33th week of gestation due to headache, vomiting, and blurred vision. The ophthalmologic examination showed intact pupillary light reflexes and normal ophthalmoscopic findings, but no light perception in either eye. Brain computed tomography showed normal findings. HELLP syndrome and preeclampsia was diagnosed based on the findings of hypertension and proteinuria as well as laboratory data. Prompt delivery was performed in order to achieve good maternal and neonatal outcomes.

Role of Helicobacter pylori in cirrhotic patients with dyspepsia: a 13C-urea breath test study

The role of Helicobacter pylori in dyspeptic, cirrhotic patients remains unclear. This prospective outpatient study, conducted to assess the relationship of gastroduodenal disease and H. pylori as determined by the (13C) urea breath test, enrolled 109 consecutive cirrhotic patients with dyspepsia. All patients underwent upper-gastrointestinal endoscopy, which revealed respective prevalences of peptic ulcer, gastric ulcer, and duodenal ulcer of 41.3%, 23.9%, and 22.9%; H. pylori infection was found in 52.3%. The rate of peptic ulcer disease in the H. pylori-positive (45.6%) and -negative (36.5%) groups was not significantly different; neither was the prevalence of H. pylori in patients with or without portal hypertensive gastropathy and with or without esophageal varices. The relationship between peptic ulcer disease and H. pylori in dyspeptic patients with cirrhosis appears to be weak. Likewise, no significant relationship was evident between H. pylori and portal hypertensive gastropathy or esophageal varices. This organism may not be a major pathogenetic factor in gastroduodenal diseases in dyspeptic patients with cirrhosis.

Endoscopic stenting in the treatment of bile leakage after laparoscopic cholecystectomy

BACKGROUND

Bile leakage is one of the most common complications after laparoscopic cholecystectomy surgery, and biliary decompression is a key factor in treatment. We retrospectively investigated 6 patients with bile leakage after laparoscopic cholecystectomy who were treated with endoscopic stent.

METHODS

From March 1995 to May 1999, six patients (4 men and 2 women) aged 30-64 years (mean, 51 years) with bile leakage after laparoscopic cholecystectomy were enrolled. Biliary stent (10 French, 6-10 cm) placement with (n = 4) or without (n = 2) sphincterotomy was attempted. The symptoms, results and outcomes were reviewed.

RESULTS

The interval from operation to presentation of bile leakage ranged from 1 to 10 days. Bile leakage was detected from cystic duct stump in 5 patients (83%) and from right IHD in 1 patient (17%). Plastic stent placement was successfully in all patients. Endoscopic stenting healed bile leakage successfully in 5 cases (83%). One patient required surgical correction due to persistent bile leakage. The mean duration between stent placement and cessation of bile leakage was 6.8 days (range 1 to 24 days).

CONCLUSIONS

Endoscopic stenting is a safe, rapid and effective treatment for bile leakage after laparoscopic cholecystectomy.

Efficacy of endoscopic isotonic saline-epinephrine injection for the management of active Mallory-Weiss tears

Therapeutic endoscopy with isotonic saline-epinephrine (ISE) injection is a convenient and widely used procedure for hemostasis in upper gastrointestinal bleeding. We retrospectively evaluated 36 patients (from January 1996 to April 1999) who had been diagnosed with recent or active bleeding due to Mallory-Weiss tears in emergency endoscopic examination. The endoscopic hemostatic method with ISE injection was performed in 15 of 36 patients. The other 21 patients received conservative treatment with hemodynamic support. Patient's clinical data, laboratory data, transfusion requirements, endoscopic findings, and length of hospital stays were evaluated. Initial hemoglobin was significantly lower in the ISE group than the conservative treatment group (9.74 +/- 2.86 g/dL vs. 12.57 +/- 2.80 g/dL, respectively; p < 0.01). Mean transfusion requirements were significantly higher in the ISE group than the conservative treatment group (7.26 +/- 8.78 units vs. 2.85 +/- 6.21 units, respectively; p < 0.1). Patients in the ISE group were supposed to be having a more severe bleeding episode. Most patients achieved initial hemostasis in the ISE group and the conservative treatment group (93% and 95%, respectively). The rebleeding rate was also similar in both groups (1 in 15 in the ISE group and I in 21 in the conservative treatment group). There was no significant difference in length of hospital stay and rebleeding between these two groups (3.47 +/- 1.92 days vs. 2.47 +/- 1.47 days, respectively: p = 0.89). The endoscopic ISE injection is an inexpensive, simple, convenient therapeutic method and it can achieve initial hemostasis for active Mallory-Weiss tears.

AMF-1/Gps2 binds p300 and enhances its interaction with papillomavirus E2 proteins

The cellular protein AMF-1 (Gps2) positively modulates gene expression by the papillomavirus E2 protein (D. E. Breiding et al., Mol. Cell. Biol. 17:7208-7219, 1997). We show here that AMF-1 also binds the transcriptional coactivator p300 in vitro and in vivo. E2 interacted weakly with p300. These observations led to a model in which AMF-1 recruits p300 into a complex with E2. Cotransfection of AMF-1 or p300 stimulated levels of E2-dependent transcription, while cotransfection of both AMF-1 and p300 showed an additive effect. The functional significance of p300 recruitment for E2 transactivation was evidenced by repression of E2-activated transcription by adenovirus E1A, which inhibits both coactivator and acetylase activities of p300. Antibodies to AMF-1 or E2 immunoprecipitated histone acetylase activity from cell lysates. Western blotting using antibody against acetyl-lysine failed to detect acetylation of AMF-1 or E2 in complex with p300. These results suggest that AMF-1 facilitates the recruitment of p300 and its histone acetylase activity into complexes with E2 and represents a novel mechanism of transcriptional activation.

The effectiveness of serum alpha-fetoprotein level in anti-HCV positive patients for screening hepatocellular carcinoma

BACKGROUND/AIMS

In Taiwan, most cases of hepatocellular carcinoma (HCC) are hepatitis B virus (HBV) or hepatitis C virus (HCV) related. The serum alpha-fetoprotein (AFP) level is an important factor in the diagnosis of HCC. There have been many studies discussing the role of AFP in diagnosing HBV-related HCC, but only few concerning HCV-related HCC. In this study, we aimed at analyzing the distribution of AFP levels in anti-HCV positive patients with and without HCC and evaluating the effectiveness of serum AFP levels in screening HCV-related HCC.

METHODOLOGY

From 1993-1996, we collected the AFP data of 205 HCC patients retrospectively, who were anti-HCV positive. For comparison, 131 randomized anti-HCV positive patients without evidence of HCC served as the control group. We analyzed the AFP distribution in both groups over the following ranges: < or = 5 ng/ml, > 5-20 ng/ml, > 20-50 ng/ml, > 50-100 ng/ml, > 100-200 ng/ml and > 200-400 ng/ml, and > 400 ng/ml.

RESULTS

The distributions of AFP levels in anti-HCV positive patients with HCC were 13.2%, 21.5%, 11.2%, 4.9%, 4.4%, 7.3%, and 37.6%. The distributions in anti-HCV positive patients without evidence of HCC were 34.3%, 55.0%, 8.4%, 1.5%, 0.8%, 0%, 0%.

CONCLUSIONS

We found the differences in AFP to be statistically significant between anti-HCV positive patients with and without HCC. A serum AFP level of more than 200 ng/ml highly indicates HCC. However, there is a large overlap between these 2 groups. Thus, in anti-HCV positive patients, AFP level is not a good single reference for diagnosis of HCC. Anti-HCV positive patients should be routinely screened for HCC by image studies along with serum AFP level.

Clinical impact of upper gastrointestinal tract injuries in glyphosate-surfactant oral intoxication

Fifty patients with glyphosate-surfactant oral ingestion were studied with upper gastrointestinal (UGI) endoscopic grading using Zargar's modified grading system for mucosal corrosive injury. Esophageal injury was seen in 68% of the patients, gastric injury in 72%, and duodenal injury in 16%. There were no grade 3 injuries. The upper gastrointestinal tract injuries caused by glyphosate-surfactant were minor in comparison with those by other strong acids. The WBC count, amount of glyphosate-surfactant ingested, length of hospital stay and the occurrence of serious complications increased markedly in the group which had grade 2 esophageal injuries. Thus, the severity of the esophageal injuries may be a prognostic factor for the patient with glyphosate-surfactant ingestion. The UGI endoscopy may be indicated for grading esophageal injury in patients who have ingested glyphosate-surfactant in amounts greater than 100 ml. Physicians should pay more attention to the patients with grade 2 or 3 esophageal injuries to prevent serious complications and to provide aggressive supportive care.

Enhanced binding to origin DNA at low pH enables easy detection of polyomavirus large T antigen by gel mobility shift assay of unfixed complexes

Enhanced, stable binding by polyomavirus large T antigen to the viral DNA replication origin at pH 6 allowed the development of a gel mobility shift assay for the detection of large T antigen. Such assays were not possible at pH 7.6 without previous fixation, due to instability of the complexes. We demonstrated that the gel mobility shift assay at pH 6 is very sensitive, allowing the detection of as little as 5 ng large T antigen, and is highly specific for DNA containing G(A/G)GGC target sequences. This method was used to detect large T antigen in crude cell lysates from transformed yeast cell lines or nuclear extracts from infected insect cells. Large T antigen-DNA complexes remained at or near the loading well in 5% acrylamide or 1.5% agarose gels, indicating that these complexes are very large. Glycerol gradient analysis showed that protein-DNA complexes formed at pH 6 were massive, and that large T antigen also formed large complexes when incubated at low pH in the absence of DNA. These results show that pH has a major effect on binding of large T antigen to its multiple target sites in the viral origin of DNA replication, presumably by affecting protein-protein interactions that are important for the stability of large T antigen-DNA complexes.

Polyomavirus large T antigen binds cooperatively to its multiple binding sites in the viral origin of DNA replication

Polyomavirus large T antigen binds to multiple 5'-G(A/G)GGC-3' pentanucleotide sequences in sites 1/2, A, B, and C within and adjacent to the origin of viral DNA replication on the polyomavirus genome. We asked whether the binding of large T antigen to one of these sites could influence binding to other sites. We discovered that binding to origin DNA is substantially stronger at pH 6 to 7 than at pH 7.4 to 7.8, a range often used in DNA binding assays. Large T antigen-DNA complexes formed at pH 6 to 7 were stable, but a fraction of these complexes dissociated at pH 7.6 and above upon dilution or during electrophoresis. Increased binding at low pH is therefore due at least in part to increased stability of protein-DNA complexes, and binding at higher pH values is reversible. Binding to fragments of origin DNA in which one or more sites were deleted or inactivated by point mutations was measured by nitrocellulose filter binding and DNase I footprinting. The results showed that large T antigen binds cooperatively to its four binding sites in viral DNA, suggesting that the binding of this protein to one of these sites stabilizes its binding to other sites via protein-protein contacts. Sites A, B, and C may therefore augment DNA replication by facilitating the binding of large T antigen to site 1/2 at the replication origin. ATP stabilized large T antigen-DNA complexes against dissociation in the presence, but not the absence, of site 1/2, and ATP specifically enhanced protection against DNase I digestion in the central 10 to 12 bp of site 1/2, at which hexamers are believed to form and begin unwinding DNA. We propose that large T antigen molecules bound to these multiple sites on origin DNA interact with each other to form a compact protein-DNA complex and, furthermore, that ATP stimulates their assembly into hexamers at site 1/2 by a "handover" mechanism mediated by these protein-protein contacts.

Production of active polyomavirus large T antigen in yeast Pichia pastoris

The coding region of polyomavirus large T antigen was engineered into the genome of the methylotrophic yeast Pichia pastoris by use of the vector pHIL-D2. Expression of large T antigen was induced by methanol under the control of the strong alcohol oxidase (AOX1) promoter. Large T antigen was purified by immunoaffinity chromatography. We showed that yeast-derived large T antigen bound specifically to a DNA fragment that contains the polyomavirus replication origin, protected the four known major binding sites in the origin against DNase I digestion, and could unwind the strands of an origin-containing DNA fragment in an ATP-dependent manner. This system therefore provides a convenient and inexpensive source of biologically active polyomavirus large T antigen for in vitro studies.

Mechanical strain increases endothelin-1 gene expression via protein kinase C pathway in human endothelial cells

Vascular endothelial cells (ECs) are constantly subjected to mechanical strain due to relaxation and contraction of vessel walls. The effects of cyclical strain on endothelin-1 (Et-1) secretion and Et-1 mRNA levels in human umbilical vein ECs were examined. Cultured ECs grown on a flexible membrane base were deformed by negative pressure (16 kPa at 60 cycles/min). Cells subjected to strain showed increased Et-1 secretion (0.54 ng/hr/10(6) cells) compared with unstrained control cells (0.22 ng/hr/10(6) cells). Northern blot analysis of cells strained for 2 hours or longer demonstrated a sustained elevated Et-1 mRNA level at more than double the level in unstrained controls. This strain-induced ET-1 mRNA level returned to its basal level 2 hours after the release of strain. Cells treated with actinomycin D before or during strain treatment showed no strain-induced gene expression. Pretreatment of ECs with a protein kinase C (PKC) inhibitor, Calphostin C, strongly inhibited the strain-induced Et-1 gene expression. Pretreatment of ECs with cAMP- or cGMP-dependent protein kinase inhibitors (KT5720 or KT5823) only partially inhibited the increased Et-1 mRNA levels in strain-treated cells. EGTA strongly inhibited the Et-1 gene expression. The intracellular calcium chelator BAPTA/AM also showed an inhibitory effect on Et-1 mRNA levels. We conclude that mechanical strain can stimulate the secretion of Et-1 from ECs by increasing Et-1 mRNA levels via transcription, and that this gene induction is mediated predominantly via the PKC pathway and requires extracellular Ca2+. This strain-induced Et-1 gene expression in ECs may contribute to the regulation of vascular tone and structure in normal and pathological states of the cardiovascular system.