Conjugation of monoclonal antibodies with TETA using activated esters: biological comparison of 64Cu-TETA-1A3 with 64Cu-BAT-2IT-1A3

A simple method for conjugation of monoclonal antibodies (mAbs) with the chelating agent 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA), has been developed using commercially available reagents. This method involved activation of a single carboxyl group of TETA with N-hydroxysulfosuccinimide and 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The resulting activated ester of TETA was reacted with the anti-colorectal carcinoma mAb 1A3 at molar ratios ranging from 10:1 to 100:1 to give immunoconjugates modified with an average of 0.4 to 2.0 functional chelators per antibody molecule. The TETA-1A3 conjugate was labeled with 64Cu at specific activities as high as 15.4 microCi/microgram, and the radiolabeled mAb exhibited high in vitro serum stability and minimal loss of immunoreactivity. The biodistribution of 64Cu-labeled TETA-1A3 in hamsters bearing GW39 human colon carcinoma xenografts was compared to that of 64Cu-BAT-2IT-1A3 (BAT = 6-(p-bromoacetamidobenzyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8,11- tetraacetic acid; 2IT = 2-iminothiolane). Both conjugates showed high tumor uptake (6.60-9.05% injected dose/gram) from 24 to 48 h post-injection and generally similar blood clearance and non-target organ uptakes. Human absorbed dose estimates derived from the hamster biodistribution data showed the critical organs for both conjugates to be the large intestine and the red marrow. Our results suggest that the in vitro and in vivo performance characteristics of 64Cu-TETA-1A3 compare favorably with those of 64Cu-BAT-2IT-1A3 and that further evaluation of the diagnostic and therapeutic efficacy of 64Cu-TETA-1A3 is warranted.

Investigation of the role of the domain linkers in separate site catalysis by Clostridium symbiosum pyruvate phosphate dikinase

Pyruvate phosphate dikinase (PPDK) catalyzes the reversible reaction: ATP + P(i) + pyruvate <--> AMP + PP(i) + PEP using Mg2+ and NH4+ ions as cofactors. The reaction takes place in three steps, each mediated by a carrier histidine residue located on the surface of the central domain of this three-domain enzyme: (1) E-His + ATP <--> E-His-PP.AMP, (2) E-His-PP.AMP + P(i) <--> E-His-P + AMP + PP(i), (3) E-His-P + pyruvate <--> E-His + PEP. The first two partial reactions are catalyzed at an active site located on the N-terminal domain, and the third partial reaction is catalyzed at an active site located on the C-terminal domain. For catalytic turnover, the central domain travels from one terminal domain to the other. The goal of this work is to determine whether the two connecting linkers direct the movement of the central domain between active sites during catalytic turnover. The X-ray crystal structure of the enzyme suggests interaction between the two linkers that may result in their coordinated movement. Mutations were made at the linkers for the purpose of disrupting the linker-linker interaction and, hence, synchronized linker movement. Five linker mutants were analyzed. Two of these contain 4-Ala insertions within the solvated region of the linker, and three have 3-residue deletions in this region. The efficiencies of the mutants for catalysis of the complete reaction as well as the E-His + ATP <--> E-His-PP.AMP partial reaction at the N-terminal domain and the E-His + PEP <--> E-His-P + pyruvate reaction at the C-terminal domain were measured to assess linker function. Three linker mutants are highly active catalysts at both active sites, and the fourth is highly active at one site but not the other. These results are interpreted as evidence against coordinated linker movement, and suggest instead that the linkers move independently as the central domain travels between active sites. It is hypothesized that while the linkers play a passive role in central domain-terminal domain docking, their structural design minimizes the conformational space searched in the diffusion process.

Investigation of the catalytic site within the ATP-grasp domain of Clostridium symbiosum pyruvate phosphate dikinase

Pyruvate phosphate dikinase (PPDK) catalyzes the interconversion of ATP, P(i), and pyruvate with AMP, PP(i), and phosphoenolpyruvate (PEP) in three partial reactions as follows: 1) E-His + ATP --> E-His-PP.AMP; 2) E-His-PP.AMP + P(i) --> E-His-P.AMP.PP(i); and 3) E-His-P + pyruvate --> E.PEP using His-455 as the carrier of the transferred phosphoryl groups. The crystal structure of the Clostridium symbiosum PPDK (in the unbound state) reveals a three-domain structure consisting of consecutive N-terminal, central His-455, and C-terminal domains. The N-terminal and central His-455 domains catalyze partial reactions 1 and 2, whereas the C-terminal and central His-455 domains catalyze partial reaction 3. Attempts to obtain a crystal structure of the enzyme with substrate ligands bound at the nucleotide binding domain have been unsuccessful. The object of the present study is to demonstrate Mg(II) activation of catalysis at the ATP/P(i) active site, to identify the residues at the ATP/P(i) active site that contribute to catalysis, and to identify roles for these residues based on their positions within the active site scaffold. First, Mg(II) activation studies of catalysis of E + ATP + P(i) --> E-P + AMP + PP(i) partial reaction were carried out using a truncation mutant (Tem533) in which the C-terminal domain is absent. The kinetics show that a minimum of 2 Mg(II) per active site is required for the reaction. The active site residues used for substrate/cofactor binding/activation were identified by site-directed mutagenesis. Lys-22, Arg-92, Asp-321, Glu-323, and Gln-335 mutants were found to be inactive; Arg-337, Glu-279, Asp-280, and Arg-135 mutants were partially active; and Thr-253 and Gln-240 mutants were almost fully active. The participation of the nucleotide ribose 2'-OH and alpha-P in enzyme binding is indicated by the loss of productive binding seen with substrate analogs modified at these positions. The ATP, P(i), and Mg(II) ions were docked into the PPDK N-terminal domain crevice, in an orientation consistent with substrate/cofactor binding modes observed for other members of the ATP-Grasp fold enzyme superfamily and consistent with the structure-function data. On the basis of this docking model, the ATP polyphosphate moiety is oriented/activated for pyrophosphoryl transfer through interaction with Lys-22 (gamma-P), Arg-92 (alpha-P), and the Gly-101 to Met-103 loop (gamma-P) as well as with the Mg(II) cofactors. The P(i) is oriented/activated for partial reaction 2 through interaction with Arg-337 and a Mg(II) cofactor. The Mg(II) ions are bound through interaction with Asp-321, Glu-323, and Gln-335 and substrate. Residues Glu-279, Asp-280, and Arg-135 are suggested to function in the closure of an active site loop, over the nucleotide ribose-binding site.

[Evaluation of diagnosis of endometrial hyperplasia by curettage]

OBJECTIVE

To evaluate the accuracy of diagnosing endometrial hyperplasia (EH) by curettage.

METHODS

150 cases who had been diagnosed as EH by curettage and received hysterectomy shortly after were studied retrospectively. All of the specimens obtained from curettage and operation underwent pathological examination. The results of pathological diagnosis of these two kinds of specimens were compared. Proliferating cell nuclear antigen (PCNA) expression was examined by immunohistochemistry in 38 cases diagnosed as complex atypical hyperplasia (CAH).

RESULTS

Fifty-three cases were diagnosed as simple hyperplasia (SH), eleven cases as complex hyperplasia (CH), twenty-six cases as simple atypical hyperplasia (SAH), and sixty cases as CAH by curettage. Rediagnosis was made for all patients after hysterectomy. Pathological examination of the specimens from operation diagnosed 65 cases as SH, 7 cases as CH, 15 cases as SAH, 29 cases as CAH, and 34 cases as EC. The general accuracy of histological diagnosis by curettage was 76.7% approximately 92.6%. Coexistence with EC was more common in cases with SAH and CAH than in cases with SH and CH (chi(2) = 26.3, P < 0.01). Coexistence with EC was more common in cases with CAH than in cases with SAH (chi(2) = 9.78, P < 0.005). Among the CAH cases, coexistence with EC was more common in postmenopausal patients than in premenopausal patients (chi(2) = 3.93, P < 0.05). Among the CAH cases, the positive rate of PCNA expression was higher and strength of positivity greater in those cases with EC (Uc = 3.66, P < 0.05).

CONCLUSION

The accuracy of curettage is rather high in diagnosing SH and relatively low in diagnosing CAH. CAH often coexists with EC. Examination of PCNA expression may help differentiate between CAH and EC.

Growth inhibition of interleukin-2 receptor gene-transduced peripheral blood lymphocytes on human ovarian cancer cells

OBJECTIVE

To investigate the growth inhibition of interleukin-2 receptor (IL-2R) gene-transduced peripheral blood lymphocytes (PBLs) on human ovarian cancer cells.

METHODS

Interleukin-2 (IL-2) and IL-2R genes were transfected into human ovarian cancer cell line 3AO and PBLs, respectively, using the same Fugene vector. Twenty-four hours later transfected and nontransfected PBLs were cocultured with transfected and nontransfected 3AO for 48 hours. cytotoxicity of PBLs on 3AO was detected by the MTT assay.

RESULTS

The morphology of IL-2-transduced 3AO and IL-2R-transduced PBLs remained unchanged. 3AO cells could be transfected with the IL-2 gene and expressed IL-2 mRNA, and PBLs could be transfected with the IL-2R gene and expressed IL-2R mRNA. IL-2 transduced 3AO cells enhanced their response to the cytotoxicity of PBLs. Furthermore, growth inhibition of PBLs to 3AO cells increased significantly when the IL-2R was transfected into PBLs and when the IL-2 gene was transfected into 3AO cells and the two were combined.

CONCLUSIONS

IL-2R gene transduced PBLs are able to enhance their cytotoxicity on IL-2 gene transduced ovarian cancer cells. This method may be a new way to investigate IL-2 gene therapy for ovarian cancer.

Differential splicing of Pneumocystis carinii f. sp. carinii inosine 5'-monophosphate dehydrogenase pre-mRNA

Inosine 5'-monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme in guanine nucleotide metabolism that has drawn attention as a drug target in several organisms. Pneumocystis carinii f. sp. carinii IMPDH mRNA (GeneBank Accession No: U42442) previously identified from cultured organisms yielded a predicted amino acid sequence about 70 amino acids shorter at the amino terminus than IMPDH from other species. Recent research has shown that the amino terminal region is important for enzyme activity, suggesting that the previous putative P. carinii IMPDH might not represent full length, functional enzyme. To test this hypothesis, RT-PCR was performed with total RNA isolated from P. carinii f. sp. carinii. Three IMPDH splicing variants were found and splicing preference was observed: P. carinii isolated from infected rat lung contained primarily splicing variant one (introns two and four deleted), but organisms from spinner flask culture contained primarily splicing variant three (all four introns deleted). Importantly, splicing variant one (GeneBank Accession No: AF196975) contained an open reading frame for 529 amino acids, a size comparable to that of other eukaryotic IMPDH forms. The other variants contained the same open reading frame (454 amino acids) previously reported. Sequence analysis and complementation studies suggest variant one represents the full length, catalytically active form of P. carinii IMPDH. The differential splicing of the enzyme may reflect a mechanism by which the organism regulates the expression of IMPDH in response to environmental stresses.

[Obesity, hypertension, and diabetes mellitus among school children in Ouagadougou (Burkina Faso)]

This paper deals with the findings of a survey conducted at the school environnement in Ouagadougou. Three factors of cardiovascular risks were identified: obesity, high blood pressure, and diabete millitus. The survey was based on a sample of 1470 students from primary and secondary schools consisted in taking their blood pressure, measuring they weight and height and glycaemia using dextrostix. Of the 1470 students targeted, 668 were girls and 782 were boys. Their age ranges between 4 and 25 years with average age of 13.8 years. 55 % of the students had an average socio-economic backgrounds. 58 students or 3.94% had high blood pressure including 50 cases of maximum high blood pressure and 8 cases of confirmed high blood pressure (HBP). A diastolic HBP predominance among 48 cases or 3.26% was also recorded. While 1 case showed systolic HBP, 6 were systolo-diastolic. The quetelet index used to determine obesity revealed 28 cases of excess in weight or 1.90% of the cases and 4 cases of obesity, or 0.28%. The predominance of excess in weight was statistically significant among girls. Only 1 case of obesity was associated with high blood pressure. No case of diabetes was identified. The factors of cardiovascular risk seem to be statistically important in school environnement in Ouagadougou. However, an muticentered study is recommended, as it will lead to an exhaustive knowledge of the prevalence of these factors of cardiovascular risk.

Identification of domain-domain docking sites within Clostridium symbiosum pyruvate phosphate dikinase by amino acid replacement

Potential domain-domain docking residues, identified from the x-ray structure of the Clostridium symbiosum apoPPDK, were replaced by site-directed mutagenesis. The steady-state and transient kinetic properties of the mutant enzymes were determined as a way of evaluating docking efficiency. PPDK mutants, in which one of two stringently conserved docking residues located on the N-terminal domain (Arg(219) and Glu(271)) was substituted, displayed largely unimpeded catalysis of the phosphoenolpyruvate partial reaction at the C-terminal domain, but significantly impaired catalysis (>10(4)) of the ATP pyrophosphorylation of His(455) at the N-terminal domain. In contrast, alanine mutants of two potential docking residues located on the N-terminal domain (Ser(262) and Lys(149)), which are not conserved among the PPDKs, exhibited essentially normal catalytic turnover. Arg(219) and Glu(271) were thus proposed to play an important role in guiding the central domain and, hence, the catalytic His(455) into position for catalysis. Substitution of central domain residues Glu(434)/Glu(437) and Thr(453), the respective docking partners of Arg(219) and Glu(271), resulted in mutants impaired in catalysis at the ATP active site. The x-ray crystal structure of the apo-T453A PPDK mutant was determined to test for possible misalignment of residues at the N-terminal domain-central domain interface that might result from loss of the Thr(453)-Glu(271) binding interaction. With the exception of the mutation site, the structure of T453A PPDK was found to be identical to that of the wild-type enzyme. It is hypothesized that the two Glu(271) interfacial binding sites that remain in the T453A PPDK mutant, Thr(453) backbone NH and Met(452) backbone NH, are sufficient to stabilize the native conformation as observed in the crystalline state but may be less effective in populating the reactive conformation in solution.

[The correlation of cytokines TNF alpha, IFN-gamma, Epo with anemia in rheumatoid arthritis]

OBJECTIVE

To elucidate the characteristics of anemia of chronic disease(ACD) in rheumatoid arthritis(RA), and the role of TNF alpha, IFN-gamma and Epo in the pathogenesis of ACD.

METHOD

Serum TNF alpha and IFN-gamma levels in RA patients and serum Epo levels in RA with ACD were measured by ELISA. Serum iron status profile in RA patients were also detected. The effects of TNF alpha and IFN-gamma on cobalt-induced erythropoietin production in human hepatic cancer cells(HepG2) were examined. The effect of TNF alpha and IFN-gamma erythroid colony formation (CFU-E and BFU-E) of normal bone marrow cells, and the effect of serum from RA patients and Epo on CFU-E yields of RA bone marrow cells.

RESULT

Serum TNF alpha or IFN-gamma in RA and RA with ACD patients were higher than those in normal controls, and were inversely correlated with hemoglobin, and serum iron levels. Serum Epo levels in ACD patients were lower than those in iron-deficiency anemia patients with comparable hemoglobin level. TNF alpha and IFN-gamma could specifically inhibit cobalt-induced Epo production in HepG2 cells, and suppressed normal bone marrow BFU-E and CFU-E growth in a dose-dependent manner. Bone marrow CFU-E yields of RA patients were also suppressed by their own serum. The inhibitory effects of TNF alpha, IFN-gamma or serum from RA patients on erythroid colony formation could be corrected by the addition of rhEpo.

CONCLUSION

It suggested that there were hematopoietic inhibiting factors in the serum of RA patients. TNF alpha or IFN-gamma was involved in the pathogenesis of anemia in RA patients. Administration of rhEpo might be beneficial for anemia of RA patients.

The possible subduction of continental material to depths greater than 200 km

Determining the depth to which continental lithosphere can be subducted into the mantle at convergent plate boundaries is of importance for understanding the long-term growth of supercontinents as well as the dynamic processes that shape such margins. Recent discoveries of coesite and diamond in regional ultrahigh-pressure (UHP) metamorphic rocks has demonstrated that continental material can be subducted to depths of at least 120 km (ref. 1), and subduction to depths of 150-300 km has been inferred from garnet peridotites in orogenic UHP belts based on several indirect observations. But continental subduction to such depths is difficult to trace directly in natural UHP metamorphic crustal rocks by conventional mineralogical and petrological methods because of extensive late-stage recrystallization and the lack of a suitable pressure indicator. It has been predicted from experimental work, however, that solid-state dissolution of pyroxene should occur in garnet at depths greater than 150 km (refs 6-8). Here we report the observation of high concentrations of clinopyroxene, rutile and apatite exsolutions in garnet within eclogites from Yangkou in the Sulu UHP metamorphic belt, China. We interpret these data as resulting from the high-pressure formation of pyroxene solid solutions in subducted continental material. Appropriate conditions for the Na2O concentrations and octahedral silicon observed in these samples are met at depths greater than 200 km.

[Experimental study on effect of Shenmai injection in improving contractility of fatigue diaphragm in rats]

OBJECTIVE

To study and compare the effects of Shenmai Injection (SMI) and aminophylline on pathogenesis and developing process of diaphragmatic fatigue.

METHODS

SMI group, aminophylline group, SMI plus aminophylline group and control group of isolated rat's diaphragmatic muscular strip of equal length were set up, and electric stimulation was applied. Changes of related parameters in the fatigue inducing and recovery process were estimated.

RESULTS

During fatigue inducing process, the lowering on maximal rates of relaxation (dR/dtmax) was earlier than that on maximal contraction peak (Pt) and contraction rate (dT/dtmax), and restoring of these parameters were restored later and incompletely. SMI could prolong the time Pt needed for reducing 50%, speed up the restoration of Pt. Although aminophylline could increase Pt, it shortened the fatigue inducing time and postponed the recovery.

CONCLUSION

Disturbance in the function of relaxation plays important role in diaphragm fatigue induction. Through strengthening the capability to relax, SMI could improve the function of fatigue diaphragm. Aminophylline would damage the relaxation function together with the increasing contraction of diaphragm simultaneously, and this side-effect could be antagonised partly by SMI.

Mutational analysis of the Helicobacter pylori vacuolating toxin amino terminus: identification of amino acids essential for cellular vacuolation

The functional importance of the amino terminus of the Helicobacter pylori vacuolating cytotoxin (VacA) was investigated by analyzing the relative levels of vacuolation of HeLa cells transfected with plasmids encoding wild-type and mutant forms of the toxin. Notably, VacA's intracellular activity was found to be sensitive to small truncations and internal deletions at the toxin's amino terminus. Moreover, alanine-scanning mutagenesis revealed the first VacA point mutations (at proline 9 or glycine 14) that completely abolish the toxin's intracellular activity.

Nitroblue tetrazolium blocks BK channels in cerebrovascular smooth muscle cell membranes

The effects of p-nitroblue tetrazolium (NBT) on large conductance, calcium-activated potassium channels (BK channels) in enzymatically dispersed rat cerebrovascular smooth muscle cells (CVSMCs) were examined. Patch clamp methods were employed to record single BK channel currents from inside-out patches of CVMC membrane maintained at 21 - 23 degrees C. When applied to the cytoplasmic face of inside-out membrane patches (internally applied NBT), micromolar concentrations of NBT reversible reduced the mean open time of BK channels, without changing channel conductance. NBT altered the frequency distribution of BK channel open times from a two exponential to a single exponential form. In the absence of NBT, mean channel open time increased on membrane depolarization. In the presence of internally applied NBT, mean channel open became essentially independent of membrane potential. Internally applied NBT also reduced the mean closed time of BK channels when measured at membrane potentials in the range -80 mV to +20 mV. The combined effects of internal NBT on mean open and closed times resulted in the suppression of BK channel open probability when measured at positive membrane potentials. When applied to the external membrane face, micromolar concentrations of NBT reduced mean channel open time progressively as the membrane was hyperpolarized, and also reduced open probability at negative membrane potentials. A model is proposed in which NBT alters channel gating by binding to a site at or near to the cytoplasmic membrane face. Externally applied NBT suppressed BK channel open probability at concentrations which also inhibit nitric oxide synthase (NOS). Therefore, the potential role of potassium channel block in NBT actions previously attributed to NOS inhibition is discussed.

A telemedicine management model based on message-trigger service

A telemedicine system model, based on a message-trigger service, is described. This model distributes system applications on multiple computers and establishes a communication platform to exchange messages among all applications. By broadcasting event messages, an application is able to trigger a set of local and remote services. At the same time, a protocol for message exchange is proposed to fulfill cooperation of applications. To validate the model, a teleconsultation system is designed. The results indicate that the model has good compatibility and that the characteristics are easy to implement.

[Studies on 5 kinds of methods combination for detection of smear and culture negative pulmonary tuberculosis]

OBJECTIVE

To evaluate the diagnostic value of 5 kinds of methods used jointly for smear and culture negative pulmonary tuberculosis.

METHODS

The high specificity methods were PCR examination for sputum TB-DNA, immunological examination (ELISA method) for serum LAM IgG, PPD IgG, SCIC and PPD 0.1 U skin test. Smear and culture positive cases were 31, smear and culture negative 54, healthy control 53, other lung disease 30. Methods were used for every case synchronously, then the sensitivity and specificity of single method and the diagnostic value of single and joint examination for smear and culture negative patients were evaluated.

RESULTS

In single examination sensitivity of PCR, LAM IgG, PPD IgG, SCIC, PPD 0.1 U was 96.8%, 69.2%, 62.1%, 32.0%, 53.8% respectively; specificity was 96.2%, 98.1%, 98.1%, 98.1% correspondingly. The positive detection rate of single examination for sputum TB negative patients was just 21.4%-44.4%. In combination examination the positive rates increased remarkblely by the number combined from 2 to 5, they were 66.9%, 70.5%, 80.4%, 85.7% respectively and they were more notable than that of TB positive group. The specificity of combination examination was slightly decreased by the number combined. It decreased just by 9% and the specificity of most examination methods kept on no less than 90%.

CONCLUSIONS

For diagnosis of smear and culture negative pulmonary tuberculosis combination examination using the high specificity methods can increase the sensitivity obviously and the specificity just decrease slightly. It is valuable for widely use of combination method in detection of smear and culture negative patients.

A Telemedicine Management Model Based on Message-Trigger Service

A telemedicine system model, based on a message-trigger service, is described. This model distributes system applications on multiple computers and establishes a communication platform to exchange messages among all applications. By broadcasting event messages, an application is able to trigger a set of local and remote services. At the same time, a protocol for message exchange is proposed to fulfill cooperation of applications. To validate the model, a teleconsultation system is designed. The results indicate that the model has good compatibility and that the characteristics are easy to implement.

Characterization of a novel porcine endothelin(B) receptor splice variant

Screening of porcine cerebellum cDNA library with porcine endothelin(B) (ET(B)) receptor cDNA revealed a novel ET(B) receptor cDNA that is distinctly different from the wild-type ET(B) receptor in length and the amino acid sequence at the C-terminal end. This sequence appears to represent alternate splicing of the carboxy terminal end of ET(B) receptor, resulting in a polypeptide of 429 amino acids in length, which is 14 amino acids shorter than the wild-type porcine ET(B) receptor. Characterization of the wild-type and alternately spliced ET(B) receptors expressed in COS cells revealed that both receptors displayed very similar binding [apparent dissociation constant (K(d)) and maximum binding (B(max)) for (125)I-ET-1 were 71 pM and 1.6 pmol/mg protein for wild-type and 81 pM and 1.2 pmol/mg protein for splice variant ET(B) receptors] as well as functional properties. These data suggest that the differences in the amino acids at the C-terminal end had no effect on binding or functional coupling of these alternately spliced ET(B) receptors.

A dominant negative mutant of Helicobacter pylori vacuolating toxin (VacA) inhibits VacA-induced cell vacuolation

Most Helicobacter pylori strains secrete a toxin (VacA) that causes structural and functional alterations in epithelial cells and is thought to play an important role in the pathogenesis of H. pylori-associated gastroduodenal diseases. The amino acid sequence, ultrastructural morphology, and cellular effects of VacA are unrelated to those of any other known bacterial protein toxin, and the VacA mechanism of action remains poorly understood. To analyze the functional role of a unique strongly hydrophobic region near the VacA amino terminus, we constructed an H. pylori strain that produced a mutant VacA protein (VacA-(Delta6-27)) in which this hydrophobic segment was deleted. VacA-(Delta6-27) was secreted by H. pylori, oligomerized properly, and formed two-dimensional lipid-bound crystals with structural features that were indistinguishable from those of wild-type VacA. However, VacA-(Delta6-27) formed ion-conductive channels in planar lipid bilayers significantly more slowly than did wild-type VacA, and the mutant channels were less anion-selective. Mixtures of wild-type VacA and VacA-(Delta6-27) formed membrane channels with properties intermediate between those formed by either isolated species. VacA-(Delta6-27) did not exhibit any detectable defects in binding or uptake by HeLa cells, but this mutant toxin failed to induce cell vacuolation. Moreover, when an equimolar mixture of purified VacA-(Delta6-27) and purified wild-type VacA were added simultaneously to HeLa cells, the mutant toxin exhibited a dominant negative effect, completely inhibiting the vacuolating activity of wild-type VacA. A dominant negative effect also was observed when HeLa cells were co-transfected with plasmids encoding wild-type and mutant toxins. We propose a model in which the dominant negative effects of VacA-(Delta6-27) result from protein-protein interactions between the mutant and wild-type VacA proteins, thereby resulting in the formation of mixed oligomers with defective functional activity.

Analysis of flanking sequences from dissociation insertion lines: a database for reverse genetics in Arabidopsis

We have generated Dissociation (Ds) element insertions throughout the Arabidopsis genome as a means of random mutagenesis. Here, we present the molecular analysis of genomic sequences that flank the Ds insertions of 931 independent transposant lines. Flanking sequences from 511 lines proved to be identical or homologous to DNA or protein sequences in public databases, and disruptions within known or putative genes were indicated for 354 lines. Because a significant portion (45%) of the insertions occurred within sequences defined by GenBank BAC and P1 clones, we were able to assess the distribution of Ds insertions throughout the genome. We discovered a significant preference for Ds transposition to the regions adjacent to nucleolus organizer regions on chromosomes 2 and 4. Otherwise, the mapped insertions appeared to be evenly dispersed throughout the genome. For any given gene, insertions preferentially occurred at the 5' end, although disruption was clearly possible at any intragenic position. The insertion sites of >500 lines that could be characterized by reference to public databases are presented in a tabular format at http://www.plantcell. org/cgi/content/full/11/12/2263/DC1. This database should be of value to researchers using reverse genetics approaches to determine gene function.

Gene expression from the ORF50/K8 region of Kaposi's sarcoma-associated herpesvirus

The ORF50 gene of Kaposi's sarcoma (KS)-associated herpesvirus, or human herpesvirus 8 (KSHV), activates viral replication and is weakly homologous to the herpesvirus family of R transactivators; therefore, the transcription and translation events from this region of KSHV are key events in viral reactivation. We demonstrate that ORF50 is expressed in a bicistronic message after induction of the viral lytic cycle. ORF50 migrated as a series of polypeptides: the major ones as 119 and 101 kDa, respectively. Using 3' rapid amplification of cDNA ends, RT-PCR, and cDNA library screening, we demonstrate that the major ORF50 transcript also encodes K8. The ORF50/K8 transcript was resistant to cyclohexamide, whereas the K8 transcript was only partially resistant to cyclohexamide at early timepoints. Both transcripts showed partial resistance after 12 h of phorbol ester induction. Using a GAL4-ORF50 fusion protein expression vector, we demonstrate that the transactivation domain of ORF50 resides within a 160-amino-acid region of the carboxyl portion of the ORF. Upstream regions of both ORF50 and K8 have basal promoter activity in KSHV-infected cells. K8, which had sequence homology to Bzip proteins, did not activate either promoter. However, both promoters were activated after cotransfection of ORF50 in BCBL-1 cells.

The SPOROCYTELESS gene of Arabidopsis is required for initiation of sporogenesis and encodes a novel nuclear protein

The formation of haploid spores marks the initiation of the gametophytic phase of the life cycle of all vascular plants ranging from ferns to angiosperms. In angiosperms, this process is initiated by the differentiation of a subset of floral cells into sporocytes, which then undergo meiotic divisions to form microspores and megaspores. Currently, there is little information available regarding the genes and proteins that regulate this key step in plant reproduction. We report here the identification of a mutation, SPOROCYTELESS (SPL), which blocks sporocyte formation in Arabidopsis thaliana. Analysis of the SPL mutation suggests that development of the anther walls and the tapetum and microsporocyte formation are tightly coupled, and that nucellar development may be dependent on megasporocyte formation. Molecular cloning of the SPL gene showed that it encodes a novel nuclear protein related to MADS box transcription factors and that it is expressed during microsporogenesis and megasporogenesis. These data suggest that the SPL gene product is a transcriptional regulator of sporocyte development in Arabidopsis.

Androgen and epidermal growth factor down-regulate cyclin-dependent kinase inhibitor p27Kip1 and costimulate proliferation of MDA PCa 2a and MDA PCa 2b prostate cancer cells

Low levels of p27Kip1 in primary prostate cancer specimens have been shown to be associated with higher rates of disease recurrence and poor rates of disease-free survival in patients with localized disease. In this study, we provide the first direct evidence showing that dihydrotestosterone (DHT), a major proliferation regulator of prostate cancer, can down-regulate p27Kip1 and stimulate cyclin-dependent kinase-2 (CDK2) activity in established prostate cancer cell lines. We investigated the cooperative effects of DHT and epidermal growth factor (EGF) on the proliferation of androgen-responsive MDA PCa 2a and MDA PCa 2b prostate cancer cells. DHT and EGF each stimulated proliferation of these cells, but exposure of the cells to DHT and EGF together stimulated greater proliferation. Stimulation of cell proliferation by DHT and/or EGF was associated with increased CDK2 activity and a decreased level of p27Kip1. There seems to be a positive feedback stimulation loop between androgen-induced gene transcription and EGF-stimulated signal transduction, as one could stimulate the synthesis of the receptors for the other. Dual blockade of androgen receptor function with the antiandrogen hydroxyflutamide and EGF receptor superfamily-mediated signal transduction with the anti-EGF receptor monoclonal antibody C225 and the anti-HER2 receptor monoclonal antibody Herceptin significantly enhanced growth inhibition of the MDA PCa 2a cells. Our results demonstrate the importance of counteracting both androgen receptors and EGF receptors in the development of novel therapies for prostate cancer.