Cell growth arrest and induction of cyclin-dependent kinase inhibitor p21 WAF1/CIP1 mediated by STAT1

Signal transducers and activators of transcription (STAT) proteins can be conditionally activated in response to epidermal growth factor (EGF) and interferon (IFN)-gamma. STAT activation was correlated with cell growth inhibition in response to EGF and IFN-gamma. Activated STAT proteins specifically recognized the conserved STAT-responsive elements in the promoter of the gene encoding the cyclin-dependent kinase (CDK) inhibitor p21 WAF1/CIP1 and regulated the induction of p21 messenger RNA. IFN-gamma did not inhibit the growth of U3A cells, which are deficient in STAT1, but did inhibit the growth of U3A cells into which STAT1 alpha was reintroduced. Thus, STAT1 protein is essential for cell growth suppression in response to IFN-gamma. The STAT signaling pathway appears to negatively regulate the cell cycle by inducing CDK inhibitors in response to cytokines.

Methyl jasmonate inhibition of root growth and induction of a leaf protein are decreased in an Arabidopsis thaliana mutant

Jasmonic acid and its methyl ester, methyl jasmonate (MeJA), are plant signaling molecules that affect plant growth and gene expression. Primary root growth of wild-type Arabidopsis thaliana seedlings was inhibited 50% when seedlings were grown on agar medium containing 0.1 M MeJA. An ethyl methanesulfonate mutant (jar1) with decreased sensitivity to MeJA inhibition of root elongation was isolated and characterized. Genetic data indicated the trait was recessive and controlled by a single Mendelian factor. MeJA-induced polypeptides were detected in Arabidopsis leaves by antiserum to a MeJA-inducible vegetative storage protein from soybean. The induction of these proteins by MeJA in the mutant was at least 4-fold less in jar1 compared to wild type. In contrast, seeds of jar1 plants were more sensitive than wild type to inhibition of germination by abscisic acid. These results suggest that the defect in jar1 affects a general jasmonate response pathway, which may regulate multiple genes in different plant organs.

Adiposity, gut microbiota and faecal short chain fatty acids are linked in adult humans

BACKGROUND/OBJECTIVES

High dietary fibre intakes may protect against obesity by influencing colonic fermentation and the colonic microbiota. Though, recent studies suggest that increased colonic fermentation contributes to adiposity. Diet influences the composition of the gut microbiota. Previous research has not evaluated dietary intakes, body mass index (BMI), faecal microbiota and short chain fatty acid (SCFA) in the same cohort. Our objectives were to compare dietary intakes, faecal SCFA concentrations and gut microbial profiles in healthy lean (LN, BMI⩽25) and overweight or obese (OWOB, BMI>25) participants.

DESIGN

We collected demographic information, 3-day diet records, physical activity questionnaires and breath and faecal samples from 94 participants of whom 52 were LN and 42 OWOB.

RESULTS

Dietary intakes and physical activity levels did not differ significantly between groups. OWOB participants had higher faecal acetate (P=0.05), propionate (P=0.03), butyrate (P=0.05), valerate (P=0.03) and total short chain fatty acid (SCFA; P=0.02) concentrations than LN. No significant differences in Firmicutes to Bacteroides/Prevotella (F:B) ratio was observed between groups. However, in the entire cohort, Bacteroides/Prevotella counts were negatively correlated with faecal total SCFA (r=-0.32, P=0.002) and F:B ratio was positively correlated with faecal total SCFA (r=0.42, P<0.0001). Principal component analysis identified distinct gut microbiota and SCFA-F:B ratio components, which together accounted for 59% of the variation. F:B ratio loaded with the SCFA and not with the microbiota suggesting that SCFA and F:B ratio vary together and may be interrelated.

CONCLUSIONS

The results support the hypothesis that colonic fermentation patterns may be altered, leading to different faecal SCFA concentrations in OWOB compared with LN humans. More in-depth studies looking at the metabolic fate of SCFA produced in LN and OWOB participants are needed in order to determine the role of SCFA in obesity.

DNA looping between sites for transcriptional activation: self-association of DNA-bound Sp1

The Sp1 protein activates transcription from many eukaryotic promoters. Sp1 can act in vivo from enhancer sites that are distal to the promoter and exhibit synergistic interaction with promoter-proximal binding sites. To investigate possible protein-protein interactions between DNA-bound Sp1 molecules, we have used electron microscopy to visualize the DNA-protein complexes. At the SV40 promoter, we observed the expected localized interaction at the Sp1 sites; in addition, we found that DNA-bound Sp1 served to associate two or more DNA molecules. At a modified thymidine kinase promoter, we observed a localized interaction at each of two binding locations that were separated by 1.8 kbp; in addition, we noted a substantial fraction of DNA molecules in which the distant binding regions were joined by a DNA loop. As judged by studies with mutant Sp1 proteins, the distant interactions depended on the glutamine-rich regions of Sp1 required for transcriptional activation. We conclude that DNA-bound Sp1 can self-associate, bringing together distant DNA segments. From the correlation between DNA looping in vitro and synergistic activation of the modified thymidine kinase promoter shown previously in vivo, we suggest that Sp1 exerts its transcriptional synergism by a direct protein-protein association that loops the intervening DNA. Our experiments support the DNA-looping model for the function of transcriptional enhancers.

Activation of Stat1 by mutant fibroblast growth-factor receptor in thanatophoric dysplasia type II dwarfism

The achondroplasia class of chondrodysplasias comprises the most common genetic forms of dwarfism in humans and includes achondroplasia, hypochondroplasia and thanatophoric dysplasia types I and II (TDI and TDII), which are caused by different mutations in a fibroblast growth-factor receptor FGFR3 (ref. 1). The molecular mechanism and the mediators of these FGFR3-related growth abnormalities are not known. Here we show that mutant TDII FGFR3 has a constitutive tyrosine kinase activity which can specifically activate the transcription factor Stat1 (for signal transducer and activator of transcription). Furthermore, expression of TDII FGFR3 induced nuclear translocation of Stat1, expression of the cell-cycle inhibitor p21(WAF1/CIP1), and growth arrest of the cell. Thus, TDII FGFR3 may use Stat1 as a mediator of growth retardation in bone development. Consistent with this, Stat1 activation and increased p21(WAF1/CIP1) expression was found in the cartilage cells from the TDII fetus, but not in those from the normal fetus. Thus, abnormal STAT activation and p21(WAF1/CIP1) expression by the TDII mutant receptor may be responsible for this FGFR3-related bone disease.

DNA-looping and enhancer activity: association between DNA-bound NtrC activator and RNA polymerase at the bacterial glnA promoter

The NtrC protein activates transcription of the glnA operon of enteric bacteria by stimulating the formation of stable "open" complexes by RNA polymerase (sigma 54-holoenzyme form). To regulate the glnA promoter, NtrC binds to sites that have the properties of transcriptional enhancers: the sites will function far from the promoter and in an orientation-independent fashion. To investigate the mechanism of enhancer function, we have used electron microscopy to visualize the interactions of purified NtrC and RNA polymerase with their DNA binding sites and with each other. Under conditions that allow the formation of open complexes, about 30% of DNA molecules carry both RNA polymerase and NtrC bound to their specific sites. Of these, about 15% form looped structures in which NtrC and the RNA polymerase-promoter complex are in contact. The length of the looped DNA is that predicted from the spacing that was engineered between the enhancer and the glnA promoter (390 base pairs). As expected for activation intermediates, the looped structures disappear when RNA polymerase is allowed to transcribe the DNA. We conclude that the NtrC enhancer functions by means of a direct association between DNA-bound NtrC and RNA polymerase (DNA-looping model). Association of DNA-bound proteins appears to be the major mechanism by which different types of site-specific DNA transactions are localized and controlled.

Autocrine IL-6-induced Stat3 activation contributes to the pathogenesis of lung adenocarcinoma and malignant pleural effusion

Malignant pleural effusion (MPE) is a poor prognostic sign for patients with non-small-cell lung cancer (NSCLC). The generation of MPE is largely regulated by vascular endothelial growth factor (VEGF), and upregulation of VEGF by Stat3 has been observed in several types of tumor cells. In this study, we demonstrate constitutively activated Stat3 in several human lung cancer cell lines and in tumor cells infiltrated in the pleurae of patients with adenocarcinoma cell lung cancer (ADCLC) and MPE. The observations suggest that activated Stat3 plays a role in the pathogenesis of ADCLC. In PC14PE6/AS2 cells, a Stat3-positive human ADCLC cell line, autocrine IL-6 activated Stat3 via JAKs, not via Src kinase. PC14PE6/AS2 cells express higher VEGF mRNA and protein than do Stat3-negative PC14PE6/AS2/dnStat3 cells. In an animal model, PC14P6/AS2/dnStat3 cells produced no MPE and less lung metastasis than did PC14P6/AS2 cells. PC14PE6/AS2 cells also expressed higher VEGF protein, microvessel density, and vascular permeability in tumors than did PC14P6/AS2/dnStat3 cells. Therefore, we hypothesize that autocrine IL-6 activation of Stat3 in ADCLC may be involved in the formation of malignant pleural effusion by upregulating VEGF. Higher levels of IL-6 and VEGF were also found in the pleural fluids of patients with ADCLC than in patients with congestive heart failure. The autocrine IL-6/Stat3/VEGF signaling pathway may also be activated in patients with ADCLC and MPE. These findings provide novel targets for the management of MPE.

Differences in genotypes of Helicobacter pylori from different human populations

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.

Transport of opioids from the brain to the periphery by P-glycoprotein: peripheral actions of central drugs

Many peptides and transmitters found within the brain also have peripheral sites of action. We now demonstrate that the brain releases functionally active neurotransmitters/neuromodulators directly from the brain into the blood through a saturable P-glycoprotein (Pgp) transport system. Downregulating Pgp1 expression with antisense reduced the brain-to-blood transport of morphine, beta-endorphin and other opioids. Lowering Pgp expression significantly enhanced systemic morphine analgesia and prevented tolerance, but diminished the analgesic activity of centrally administered morphine, implying that supraspinal analgesia resulted from a combination of central and peripheral mechanisms activated by morphine transported from the brain to the blood. Similarly, mice with a disruption of the Mdr1a gene were more sensitive to systemic morphine and less sensitive to morphine given centrally. This ability of the Pgp transport system to pump functionally active compounds from the brain to periphery defines a potentially important mechanism for the central nervous system to modulate peripheral systems.

Planet Within a Planet: Rotation of the Inner Core of Earth

The time dependence of the orientation of Earth's inner core relative to the mantle was determined using a recently discovered 10-degree tilt in the axis of symmetry of the inner core's seismic-velocity anisotropy. Two methods of analyzing travel-time variations for rays traversing the inner core, on the basis of 29 years of data from the International Seismological Centre (1964-1992), reveal that the inner core appears to rotate about 3 degrees per year faster than the mantle. An anomalous variation in inner-core orientation from 1969 to 1973 coincides in time with a sudden change ("jerk") in the geomagnetic field.

Polyoma middle tumor antigen interacts with SHC protein via the NPTY (Asn-Pro-Thr-Tyr) motif in middle tumor antigen

Polyomavirus middle tumor antigen (MT) transforms a large number of cell types by binding to and modulating the activities of cellular proteins. Previous genetic analysis defined in MT an independent motif, NPTY (Asn-Pro-Thr-Tyr), required for transformation. This report demonstrates that NPTY is required for interaction between MT and SHC protein, a Src homology 2 (SH2)-containing protooncogene product implicated in activating Ras via association with GRB2 protein. SHC is phosphorylated on tyrosine and associates with GRB2 in MT-transformed cells. These effects require an intact NPTY motif in MT. SHC immunoprecipitates from MT-transformed cells possess kinase activity that phosphorylates not only SHC and MT but also the 85-kDa subunit of phosphatidylinositol 3-kinase. This result suggests that a complex exists that contains, at a minimum, MT, Src family tyrosine kinases, phosphatidylinositol 3-kinase, and SHC.

Preparations, structures, and magnetic properties of a series of novel copper(II)-lanthanide(III) coordination polymers via hydrothermal reaction

The hydrothermal reaction of Ln2O3 (Ln = Er, Gd, and Sm), pyridine-2,5-dicarboxylic acid (H2pydc), and Cu(II) reagents (CuO, Cu(OAc)2-2H2O, or CuCl2-2H2O) with a mole ratio of 1:2:4 resulted in the formation of six polymeric Cu(II)-Ln(III) complexes, [(Ln2Cu3(pydc)6(H2O)12)-4H2O]n (Ln = Er (1); Ln = Gd (2)), [(Ln4Cu2(pydc)8(H2O)12)-4H2O]n (Ln = Sm (3); Ln = Gd (4); Ln = Er (5)), and [(Gd2Cu2(pydc)4(H2O)8)-Cu(pydc)2-12H2O]n (6). 1 and 2 are isomorphous and crystallize in triclinic space group Ponebar. Compounds 3-5 are isomorphous and crystallize in monoclinic space group P2(1)/c. Compound 6 crystallizes in triclinic space group Ponebar. Complexes 1 and 2 have one-dimensional zigzag chain structures and compounds 3-5 display three-dimensional wavelike polymeric structures, while 6 has an infinite sandwich-type structure. The different structures of the complexes are induced by the different forms of Cu(II) reagents; the reactions of Cu(OAc)2-2H2O yield high Cu/Ln ratio products 1, 2, and 6, while the reactions of CuO or CuCl2-2H2O/2,2'-bipyridine results in low Cu/Ln ratio compounds 3-5. Temperature-dependent magnetic susceptibilities for 2, 4, and 5 were studied, and the thermal stabilities of complexes 2 and 4 were examined.

A multinational phase 2 study of nanoliposomal irinotecan sucrosofate (PEP02, MM-398) for patients with gemcitabine-refractory metastatic pancreatic cancer

BACKGROUND

PEP02, also known as MM-398, is a novel nanoliposomal irinotecan that has improved pharmacokinetics and tumour bio-distribution of the free drug. This phase 2 study evaluated PEP02 monotherapy as second-line treatment for pancreatic cancer.

METHODS

Patients who had metastatic pancreatic adenocarcinoma, Karnofsky performance status ≥70, and had progressed following gemcitabine-based therapy were eligible. Intravenous injection of PEP02 120 mg m(-2) was given every 3 weeks. Simon 2-stage design was used. The primary objective was 3-month survival rate (OS(3-month)).

RESULTS

A total of 40 patients were enrolled. The most common severe adverse events included neutropenia, abdominal pain, asthenia, and diarrhoea. Three patients (7.5%) achieved an objective response, with an additional 17 (42.5%) demonstrating stable disease for a minimum of two cycles. Ten (31.3%) of 32 patients with an elevated baseline CA19-9 had a >50% biomarker decline. The study met its primary end point with an OS(3-month) of 75%, with median progression-free survival and overall survival of 2.4 and 5.2 months, respectively.

CONCLUSION

PEP02 demonstrates moderate antitumour activity with a manageable side effect profile for metastatic, gemcitabine-refractory pancreatic cancer patients. Given the limited treatment options available to this patient population, a phase 3 trial of PEP02 (MM-398), referred to as NAPOLI-1, is currently underway.

Assembly of silver(I) polymers with helical and lamellar structures

The new versatile multidentate nonchelating ligand 1,2-bis[(2-pyr-imidinyl)-sulfanylmethyl]benzene (bpsb) was designed and prepared for supramolecular syntheses. Self-assembly between silver nitrate and the bpsb ligand resulted in the polymer [Ag4(bpsb)2-(NO3)4]n (1) with a single-stranded helical chain structure. Each bpsb ligand in 1 acts as a tetradentate ligand, in which two sulfur atoms and two nitrogen atoms from different pyrimidine groups coordinate to four Ag atoms in four different directions. The nitrate anions serve as a template for the formation of the helix and are either embedded in the interior of the helix or located in the flank of the helix. Self-assembly between silver perchlorate and the bpsb ligand under the same conditions gave rise to the polymer [Ag2(bpsb)3(ClO4)2]n (2) comprising a two-dimensional lamellar network containing crownlike cavities. The silver atoms in two adjacent layers are arranged staggered in 2. The two-dimensional lamellar network comprising isolated cavities of [Ag6(bpsb)6] is very different from that of usual honeycomb structures.

Cabozantinib in hepatocellular carcinoma: results of a phase 2 placebo-controlled randomized discontinuation study

Background

Cabozantinib, an orally bioavailable inhibitor of tyrosine kinases including MET, AXL, and VEGF receptors, was assessed in patients with hepatocellular carcinoma (HCC) as part of a phase 2 randomized discontinuation trial with nine tumor-type cohorts.

Patients and methods

Eligible patients had Child-Pugh A liver function and ≤1 prior systemic anticancer regimen, completed ≥4 weeks before study entry. The cabozantinib starting dose was 100 mg daily. After an initial 12-week cabozantinib treatment period, patients with stable disease (SD) per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.0 were randomized to cabozantinib or placebo. The primary endpoint of the lead-in stage was objective response rate (ORR) at week 12, and the primary endpoint of the randomized stage was progression-free survival (PFS).

Results

Among the 41 HCC patients enrolled, the week 12 ORR was 5%, with 2 patients achieving a confirmed partial response (PR). The week 12 disease control rate (PR or SD) was 66% (Asian subgroup: 73%). Of patients with ≥1 post-baseline scan, 78% had tumor regression, with no apparent relationship to prior sorafenib therapy. Alpha-fetoprotein (AFP) response (>50% reduction from baseline) occurred in 9 of the 26 (35%) patients with elevated baseline AFP and ≥1 post-baseline measurement. Twenty-two patients with SD at week 12 were randomized. Median PFS after randomization was 2.5 months with cabozantinib and 1.4 months with placebo, although this difference was not statistically significant. Median PFS and overall survival from Day 1 in all patients were 5.2 and 11.5 months, respectively. The most common grade 3/4 adverse events, regardless of attribution, were diarrhea (20%), hand-foot syndrome (15%), and thrombocytopenia (15%). Dose reductions were utilized in 59% of patients.

Conclusions

Cabozantinib has clinical activity in HCC patients, including objective tumor responses, disease stabilization, and reductions in AFP. Adverse events were managed with dose reductions.

Trial registration number

NCT00940225.

Comparison of energy intakes determined by food records and doubly labeled water in women participating in a dietary-intervention trial

The accuracy of estimates of usual energy intake derived from food records in participants of a long-term dietary-intervention trial was studied in a subset of 29 women aged 48.7+/-5.0 y and weighing 61.9+/-6.5 kg. This sample was similar to the population in the whole trial (n=715), from which it was selected in terms of age, weight, body mass index (BMI), and reported energy and fat intakes. During the validation study, reported energy intake was derived from 7 consecutive days of food records, and total energy expenditure was measured by the doubly labeled water method over 13 d. Reported energy intake (6.98+/-1.58 MJ/d) was significantly lower than energy expenditure (9.00+/-2.08MJ/d) and represented 79.8+/-17.6% of expenditure. The correlation between reported energy intake and expenditure was 0.46 (P=0.01, 95% CI: 0.15, 0.71). Body weight, BMI, height, length of time in the dietary trial, and percentage of energy from fat and carbohydrate were not significantly associated with the accuracy of reporting. These results indicate that energy intake derived from food records is an imprecise measure that substantially underestimates energy intake in middle-aged women participating in a long-term dietary-intervention trial.

Taxol from Tubercularia sp. strain TF5, an endophytic fungus of Taxus mairei

The diterpenoid taxol is an important anticancer agent used widely in the clinic. The purpose of this work was to identify a taxol-producing endophytic fungus (strain TF5) isolated from Taxus mairei and study its anticancer activities. Strain TF5 was identified as a Tubercularia sp. according to the morphology of the fungal culture, the mechanism of spore production and the characteristics of the spores. Strain TF5 produced taxol, when grown in potato dextrose liquid medium and analyzed by thin layer chromatography, high performance liquid chromatography, ultraviolet and mass spectrometry. The fungal taxol, which was isolated from the organic extract of the TF5 culture, had strong cytotoxic activity towards KB and P388 cancer cells in vitro, tested by the MTT assay. Observed with immunofluorescence and electron microscopy, the fungal taxol enhanced microtubule stability and bundling in culture cells and induced tubulin polymerization in vitro similar to the authentic taxol.

Antitumor and antifungal activities in endophytic fungi isolated from pharmaceutical plants Taxus mairei, Cephalataxus fortunei and Torreya grandis

The purpose of this work was to screen the endophytic fungi having antitumor or antifungal activity, which were isolated from the inner barks of three kinds of pharmaceutical plants, Taxus mairei, Cephalataxus fortunei and Torreya grandis, collected from Fujian province, China. Antitumor activity was studied by the MTT assay and antifungal activity was determined by observing fungal growth inhibition. 13.4% of endophytic fungi fermentation broths displayed cytotoxic activity on HL-60 cells at and below a dilution of 1:50, and 6.4% on KB cells. 52.3% of endophytic fungi fermentation broths displayed growth inhibition on at least one pathogenic fungi, such as Neurospora sp., Trichoderma sp. and Fusarium sp. Among all endophytic fungi isolated, the genus Paecilomyces sp. has the highest positive rate of antitumor and antifungal activity. These results indicate that endophytic fungi could be a promising source for antitumor and antifungal bioactive agents.

DNA looping between the origin of replication of Epstein-Barr virus and its enhancer site: stabilization of an origin complex with Epstein-Barr nuclear antigen 1

Epstein-Barr nuclear antigen 1 (EBNA-1) is the only viral protein required to support replication of Epstein-Barr virus during the latent phase of its life cycle. The DNA segment required for latent replication, oriP, contains two essential binding regions for EBNA-1, termed FR and DS, that are separated by 1 kilobase pair. The FR site appears to function as a replicational enhancer providing for the start of replication at the DS site. We have used electron microscopy to visualize the interaction of EBNA-1 with its binding sites and to study the mechanism for communication between the FR and DS sites. We have found that DNA-bound EBNA-1 forms a DNA loop between the FR and DS sites. From these results, we suggest that EBNA-1 bound to the replicational enhancer acts by a DNA-looping mechanism to facilitate the initiation of DNA replication. Occupancy of the DS site alone is highly sensitive to competition with nonspecific DNA. In contrast, occupancy of the DS site by looping from FR is largely resistant to the competitor DNA. These experiments support the concept that enhancers act in cis from nearby sites to provide a high local concentration of regulatory proteins at their target sites and to stabilize regulatory interactions.

Constitutive activation of STAT3 and STAT5 is present in the majority of nasopharyngeal carcinoma and correlates with better prognosis

Constitutively activated signal transducers and activators of transcription (STAT) factors, in particular STAT1, STAT3 and STAT5, have been demonstrated in a variety of human tumours and cancer cell lines. However, data on the expression of these STATs in nasopharyngeal carcinoma (NPC) are limited. In this study, the expression patterns of STAT1, STAT3 and STAT5 were immunohistochemically examined on the archival specimens from 61 patients with NPC. Staining results of each STATs were then correlated with the clinical parameters and prognosis of these patients. The results showed that constitutive activation of STAT3 and STAT5 was detected in the majority, 70.5 and 62.3%, respectively, of the 61 tumour specimens. Furthermore, coexpression of activated STAT3 and STAT5 was found in 54.1% of the specimens. In contrast, constitutive activated STAT1 could only be detected in 8 (13.1%) cases. Surprisingly, following radiotherapy, patients with constitutive STAT5 activation, or activation of both STAT3 and STAT5, had better disease-free survival and overall survival than those without activated STAT5. To our knowledge, this is the first report providing the overall expression patterns and prognostic significance of specific STATs in NPC.

A dominant negative mutant of the KCC1 K-Cl cotransporter: both N- and C-terminal cytoplasmic domains are required for K-Cl cotransport activity

K-Cl cotransport regulates cell volume and chloride equilibrium potential. Inhibition of erythroid K-Cl cotransport has emerged as an important adjunct strategy for the treatment of sickle cell anemia. However, structure-function relationships among the polypeptide products of the four K-Cl cotransporter (KCC) genes are little understood. We have investigated the importance of the N- and C-terminal cytoplasmic domains of mouse KCC1 to its K-Cl cotransport function expressed in Xenopus oocytes. Truncation of as few as eight C-terminal amino acids (aa) abolished function despite continued polypeptide accumulation and surface expression. These C-terminal loss-of-function mutants lacked a dominant negative phenotype. Truncation of the N-terminal 46 aa diminished function. Removal of 89 or 117 aa (Delta(N)117) abolished function despite continued polypeptide accumulation and surface expression and exhibited dominant negative phenotypes that required the presence of the C-terminal cytoplasmic domain. The dominant negative loss-of-function mutant Delta(N)117 was co-immunoprecipitated with wild type KCC1 polypeptide, and its co-expression did not reduce wild type KCC1 at the oocyte surface. Delta(N)117 also exhibited dominant negative inhibition of human KCC1 and KCC3 and, with lower potency, mouse KCC4 and rat KCC2.

The isolation and characterization of a Norwalk virus-specific cDNA

Norwalk virus, an important cause of epidemic, acute, nonbacterial gastroenteritis in adults and children, has eluded adaptation to tissue culture, the development of an animal model, and molecular cloning. In this study, a portion of the Norwalk viral genome encoding an immunoreactive region was cloned from very small quantities of infected stool using sequence-independent single primer amplification. Six overlapping complementary DNA (cDNA) clones were isolated by immunologic screening. The expressed recombinant protein from a representative clone reacted with six of seven high titer. Norwalk-specific, postinfection sera but not with corresponding preinfection sera. Nucleic acid sequence for all clones defined a single open reading frame contiguous with the lambda gt11-expressed beta-galactosidase protein. Only oligonucleotide probes specific for the positive strand (defined by the open reading frame) hybridized to an RNaseA-sensitive, DNaseI-resistant nucleic acid sequence extracted from Norwalk-infected stool. Furthermore, RNA extracted from serial postinfection, but not preinfection, stools from three of five volunteers hybridized to a Norwalk virus cDNA probe. Clone-specific oligonucleotide probes hybridized with cesium chloride gradient fractions containing purified Norwalk virion. In conclusion, an antigenic, protein-coding region of the Norwalk virus genome has been identified. This epitope has potential utility in future sero- and molecular epidemiologic studies of Norwalk viral gastroenteritis.