Purification of Moloney murine leukemia virus chromatin from infected cells by an affinity method

Our goal was to develop a system to study proteins that associate in vivo with the Moloney murine leukemia virus (M-MuLV) enhancer elements by the isolation of intact proviral chromatin. The M-MuLV long terminal repeats (LTRs) contain tandemly repeated transcriptional enhancer sequences consisting of smaller motifs that bind cellular DNA-binding proteins implicated in transcriptional regulation. The M-MuLV enhancers are also important for disease specificity and latency of disease induction. To enrich for proviral chromatin containing M-MuLV LTR sequences, an affinity purification scheme was employed that relies on the affinity of bacterial Lac repressor protein for Lac operator (LacO) DNA sequences. An infectious M-MuLV recombinant was constructed that contains bacterial LacO sequences inserted into a nonessential region downstream from the 5' LTR of the virus (M-MuLV-LacO). Nuclei from M-MuLV-LacO-infected cells were digested with PvuII (which will liberate an LTR fragment containing LacO sequences), and digested chromatin was leached from the nuclei in hypotonic buffer. M-MuLV-LacO chromatin was then recovered by binding to an affinity matrix consisting of a beta-galactosidase-Lac repressor fusion protein anchored to acrylamide beads by an anti-beta-galactosidase monoclonal antibody [7]. Specifically bound chromatin was eluted under physiological conditions by incubation with the galactose analog isopropyl-beta-D-thiogalactopyranoside. Southern blot analysis confirmed the specific enrichment of M-MuLV proviral chromatin by this method.

Design of new selective inhibitors of cyclooxygenase-2 by dynamic assembly of molecular building blocks

A method of dynamically assembling molecular building blocks - DycoBlock - has been proposed and tested by Liu et al. This method is based on multiple-copy stochastic dynamics simulation in the presence of a receptor molecule. In this method, a novel algorithm was used to dynamically assemble the molecular building blocks to form candidate compounds. Currently, some new improvements have been incorporated into DycoBlock to make it more efficient. In the new version of DycoBlock, the binding energy and solvent accessible surface area (SASA) can be used to screen the resulting compounds. A simple clustering algorithm based on molecular similarity was developed and used to classify the remaining compounds. The revised DycoBlock was tested by breaking SC-558 - a selective inhibitor of cyclooxygenase-2 (COX-2) - into building blocks and reassembling them in the active site of the enzyme. The accuracy of recovery grew to 58.8% while it was only 16.7% in the previous version. Then, thirty-three kinds of molecular building blocks were used in the design of novel inhibitors and the investigation of diversity. As a result, a total of 1441 compounds was generated with high diversity. After the first screening procedure, there remained 864 reasonable compounds. The results from clustering indicate that the structural motifs in the diarylheterocycle class of COX-2-selective inhibitors have been generated using the revised DycoBlock, and their binding modes were investigated.

Self-assembly of mesoscopically ordered chromatic polydiacetylene/silica nanocomposites

Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.

Down-regulation of matrix Gla protein messenger RNA in human colorectal adenocarcinomas

Matrix Gla protein (MGP) is a vitamin K-dependent extracellular matrix protein commonly found in a variety of tissues. In this study, we describe the potential use of MGP gene expression as the tumor marker of colorectal cancer. A decrease in expression of the MGP gene was also discovered in colorectal cancer using differential screening of cDNA libraries. The MGP expression in 80 human colorectal adenocarcinomas was quantified by a Northern blot analysis to better define the expression pattern of MGP in colorectal cancer. The expression of MGP mRNA was reduced in 63 of 80 (79%) colorectal adenocarcinomas (P<0.001) as compared to the mRNA in adjacent normal tissue, implying that a decrease in MGP expression is associated with colorectal cancer development. The proportion of tumors with downregulated expression of MGP was lower in Duke's A/B than Duke's C/D (34 of 47 versus 26 of 33, respectively) tumors and was lower in moderate differentiation than poor differentiation (44 of 64 versus 16 of 16, respectively). However, chi(2) analysis does not reveal any correlation between a loss of MGP expression and tumor progression or differentiation state. In conclusion, the downregulation of MGP mRNA generally occurs in colorectal adenocarcinomas. Although the role of MGP in cancer development is unknown, the reduced expression of MGP may be used to distinguish the normal colorectal cells from malignant cells.

Direct transformation of rodent fibroblasts by jaagsiekte sheep retrovirus DNA

Jaagsiekte sheep retrovirus (JSRV) is the causative agent of ovine pulmonary carcinoma, a unique animal model for human bronchioalveolar carcinoma. We previously isolated a JSRV proviral clone and showed that it was both infectious and oncogenic. Thus JSRV is necessary and sufficient for the development of ovine pulmonary carcinoma, but no data are available on the mechanisms of transformation. Inspection of the JSRV genome reveals standard retroviral genes, but no evidence for a viral oncogene. However, an alternate ORF in pol (orf-x) might be a candidate for a transforming gene. We tested whether the JSRV genome might encode a transforming gene by transfecting an expression plasmid for JSRV [pCMVJS21, driven by the cytomegalovirus (CMV) immediate early promoter] into mouse NIH 3T3 cells. Foci of transformed cells appeared in the transfected cultures 2-3 weeks posttransfection; cloned transformants showed anchorage independence for growth, and they expressed JSRV RNA. These results indicate that the JRSV genome contains information with direct transforming potential for NIH 3T3 cells. Transfection of a mutated version of pCMVJS21 in which the orf-x protein was terminated by two stop codons also gave transformed foci. Thus, orf-x was eliminated as the candidate transforming gene. In addition, another derivative of pCMVJS21 (pCMVJS21DeltaGP) in which the gag, pol (and orf-x) coding sequences were deleted also gave transformed foci. These results indicate that the envelope gene carries the transforming potential. This is an unusual example of a native retroviral structural protein with transformation potential.

Generation of replication-defective helper-free vectors based on simian immunodeficiency virus

A systematic study on generating simian immunodeficiency virus (SIV)-based vectors was carried out. The goal was to generate helper-free, replication-defective SIVmac-based vectors at high titers. The general approach was to cotransfect into human 293T cells a plasmid carrying the vector construct along with two helper plasmids that together expressed the SIVmac virion proteins. Initial vectors carried the bacterial beta-galactosidase gene (beta-gal). These vectors had a technical difficulty: "pseudotransduction" of beta-gal protein produced during the 293T cell transfections. As a result, infection of cultures with these vector stocks also resulted in passive transfer into, and X-gal staining of, cells that had not actually been infected by the vector. A second generation of vectors expressing the enhanced jellyfish green fluorescence protein (EGFP) was not subject to this artifact. A systematic study of the SIVmac-based EGFP vectors was carried out. Helper-free vector stocks were obtained when helper plasmids lacking the SIVmac packaging signals were used. By employing envelope helper plasmids derived from different SIVmac isolates, it was possible to generate SIVmac-based vectors pseudotyped with envelope proteins of different cell tropism. Optimization of vector and helper plasmid structures, transfection conditions, and infection procedures ultimately yielded vector titers in excess of 10(6)/ml.

Use of helper-free replication-defective simian immunodeficiency virus-based vectors to study macrophage and T tropism: evidence for distinct levels of restriction in primary macrophages and a T-cell line

Cell tropism of human and simian immunodeficiency viruses (HIV and SIV, respectively) is governed in part by interactions between the viral envelope protein and the cellular receptors. However, there is evidence that envelope-host cell interactions also affect postentry steps in viral replication. We used a helper-free replication-defective SIV macaque (SIVmac)-based retroviral vector carrying the enhanced jellyfish green fluorescent protein inserted into the nef region (V1EGFP) to examine SIV tropism in a single cycle of infection. Vector stocks containing envelope proteins from three different SIVmac clones, namely, SIVmac239 (T-lymphocyte tropic [T-tropic]), SIVmac316 (macrophage tropic [M-tropic]), and SIVmac1A11 (dualtropic), were tested. SIVmac239 replicates efficiently in many human T-cell lines, but it does not efficiently infect primary rhesus macrophages. Conversely, SIVmac316 efficiently infects primary macrophages, but it does not replicate in Molt4-Clone8 (M4C8) T cells. SIVmac1A11 replicates efficiently in both cell types. When primary macrophages were infected with V1EGFP pseudotyped by SIVmac316 or SIVmac1A11 envelopes, the infection was substantially (ca. 200- to 300-fold) more efficient than for the SIVmac239 pseudotype. Thus, in primary macrophages, a major component of M versus T tropism involves relatively early events in the infection cycle. Quantitative PCR studies indicated that synthesis and transport of vector DNA into the nucleus were similar for macrophages infected with the clone 239 and 316 pseudotypes, suggesting that the restriction for SIVmac239 infection is after reverse transcription and nuclear import of viral DNA. When the same vector pseudotypes were used to infect M4C8 cells, they all showed approximately equivalent infectivities, even though replication-competent SIVmac316 does not continue to replicate in these cells. Therefore, in M4C8 cells, restriction involves a late step in the infection cycle (after proviral integration and expression). Thus, depending on the cell type infected, envelope-dependent cell interactions that govern SIV M and T tropism may involve different steps in infection.

Effect of cross-linking on the in vitro release kinetics of doxorubicin from gelatin implants

Doxorubicin is one of the most potent anti-tumor agents used generally in the treatment of bone cancer. Like other cancer chemotharepeutics, it produces undesirable side effects such as cardiotoxicity, which is especially severe when administrated via the conventional intravenous route. In order to minimize the systemic toxicities and to make this drug more suitable for the treatment of bone cancer, an implantable delivery system with cross-linked gelatin as the biodegradable matrix material was developed. This delivery system could possibly improve targeting of the drug as well as sustain the rate of release of the drug to the tumor. Glutaraldehyde was used as a cross-linking agent. Incorporation of glutaraldehyde in the matrix was needed to maintain the mechanical strength of the implant and to sustain the rate of release of the drug from the implant. Besides cross-linking the gelatin matrix, glutaraldehyde was found to cross-link the free amino group of doxorubicin. The effect of cross-linker concentration on the stability of the drug in the implant and on the rate and extent of release were also evaluated. In conclusion, cross-linked gelatin implants were developed for the local delivery of doxorubicin.

Lymphokine dependence of STAT3 activation produced by surface immunoglobulin cross-linking and by phorbol ester plus calcium ionophore treatment in B cells

Stimulation of B cells by surface immunoglobulin (sIg) triggering, or through the mitogenic combination of phorbol ester and calcium ionophore, is accompanied by activation of STAT transcription factors. The mechanism responsible for the delayed nuclear accumulation of phosphorylated STAT3 was examined in detail, focusing on the role of B cell-derived lymphokines. sIg-induced activation of STAT3 was partially inhibited in B cells obtained from IL-6- or IL-10-deficient mice, and was partially blocked by neutralizing antibodies directed against either of these lymphokines. sIg-induced STAT3 activation was completely inhibited by combining IL-6- and IL-10-specific neutralizing antibodies, or by adding individual neutralizing antibodies to B cells obtained from lymphokine-deficient animals. In contrast, IL-10 alone appeared to account for STAT3 activation resulting from B cell stimulation with phorbol ester and calcium ionophore. In keeping with these results, soluble IL-6 and IL-10 were found in supernatant fluid obtained from stimulated B cells. This work indicates that a lymphokine pathway is responsible for STAT3 activation that occurs late after B cell stimulation, and points out differences in B cell activation that result from stimulation through the antigen receptor and through pharmacological mimicry of signaling mediators.

A martyr for modernity: Qiu Jin -- feminist warrior, and revolutionary

Qui Jin, at one level, was an oriental twentieth-century Judith, the mythical Jewish widow from Bethulia who cut off the head of Holofernes, the Assyrian general besieging the city, thus saving the Israelites from destruction. Qui Jin was, as Judith was, a self-reliant heroine who when others seemed 'helpless and demoralized undertook to save them single-handedly', or in her case virtually single-handedly. This, of course, was both her making and her unmaking. In Chinese terms the story of Qui Jin, like the story of Judith if less famous, less publicised, more recent, is the story of an icon at once central and at the same time marginal to tradition. She contradicted the most cherished customs on Confucian Chinese culture. She was a radical force who thrust her way to the centre of the concentric circles of customs surrounding this culture and was pushed back to the margins by conservatism. Nevertheless Qui Jin was not without success. She challenged a long-established mythology of exclusively masterful patriarchy - and created a counter myth of purposeful patriotic feminism. She was a counter-cultural icon who changed perceptions of Chinese femininity. She gave courage, confidence and purpose to those women who came after her and absorbed her ambitions for modern Chinese womanhood. For them she was a modern national heroine and a personification of a modern nation of equal men and women. For Qui Jin the body was an instrument of female revolution to be trained, strengthened and prepared for confrontation. As a revolutionary militant she was a failure; as a revolutionary talisman she was a success. For the Chinese women of the 1911 Revolution hers was an exemplary emancipatory story: subscribe, struggle, sacrifice. Patriotism through feminism is the purpose. Her heroism was firmly outside the historic patriarchal order. Her adulation is thus all the more remarkable because of the profound traditions she rejected, the controversial mannerisms she adopted, the uncompromising attitudes she embraced. She eschewed motherhood, abandoned marriage, dismissed femininity, and yet won acclaim in the most traditional of cultures. Qui Jin was hardly a cynosure of universal acclaim but she was admired, respected and emulated by radical Chinese women and men seeking a new society accommodating women. Her modern feminism struggled to overcome an ancient patriarchy. Here was her appeal. She exuded no moral ambiguity. Consequently, if she was demonized by the conventional; she was deified by the radical - and inspired them as the contemplated and attempted to construct the future. There is a point, of course, that should not be overlooked. Qui Jin, in fact, is not divorced from occidental culture and political iconography. Qui Jin is closely associated with the attitudes, aspirations and fantasies of modern Western feminism. As Margarita Stocker observes, a 'romantic heroine, angry feminist, radical, activist is one example of a pervasive figure', in modern Western cultural mythology 'a figure we may sum up as the Woman with a Gun'. Force, that potent means to power, is available to the gun user irrespective of age of sex, with a resulting 'crucial alteration in the sexual politics of violence'. The Woman with a Gun can now be emphatically heroic - without duplicity, without deceitfulness, without subterfuge. Moral ambiguity in action has been abandoned. She becomes an unambiguous potent force - an armed woman faces an armed man on equal terms - physically, psychologically, morally. Equality offers the legal right and responsibility to kill in the name of patriotism. Modern culture has just caught up with Qui Jin.

Activation of NF kappa B and expression of ICAM-1 in ischemic-reperfused canine myocardium

Although redox-sensitive transcription factors, including nuclear factor kappa B (NF kappa B) and activator protein-1 (AP-1), have been shown to induce intercellular adhesion molecule-1 (ICAM-1) gene transcription in isolated cells, little is known about their involvement in the regulation of the ICAM-1 gene in vivo during ischemia-reperfusion. Anesthetized closed-chest dogs underwent 90 min coronary artery occlusion, followed by reperfusion for 0, 15, 30, 60, 180, or 360 min. Blood flow (fluorescent or radioactive microspheres), ICAM-1 protein expression (immunohistochemistry), ICAM-1 gene activation (Northern blotting), and nuclear DNA-binding activity of NF kappa B and AP-1 (electrophoretic mobility shift assays) were assessed in myocardial tissue samples. ICAM-1 protein was expressed constitutively on vascular endothelium, but expression levels decreased markedly during ischemia. Within 15 min reperfusion, endothelial ICAM-1 protein increased, associated with a rapid appearance of ICAM-1 mRNA. Activation of both NF kappa B and AP-1 occurred following ischemia-reperfusion, but did not coincide temporally with early post-reperfusion ICAM-1 gene induction. NF kappa B was activated during ischemia, when ICAM-1 mRNA was undetectable, and did not increase further until 60 min reperfusion, well after the increase in ICAM-1 mRNA had begun. Similarly, AP-1 did not increase until 60 min reperfusion. In non-ischemic myocardium, NF kappa B and AP-1 were both activated, but ICAM-1 mRNA did not appear until 6 h later. By immunohistology, NF kappa B (p65 subunit) and the c-Fos subunit of AP-1 were localized primarily in vascular endothelium. Reperfusion of ischemic myocardium is associated with very rapid ICAM-1 gene induction in the context of prior NF kappa B activation, without new activation of NF kappa B. In non-ischemic myocardium, ICAM-1 transcription begins hours after NF kappa B is activated. These findings support a role for NF kappa B in ICAM-1 induction in vivo, but suggest that other processes, such as oxygen-radical generation, may combine with NF kappa B to trigger an accelerated transcription of ICAM-1 following ischemia-reperfusion.

Expression and characterization of the human YWK-II gene, encoding a sperm membrane protein related to the alzheimer betaA4-amyloid precursorprotein

The YWK-II cDNA, RSD-2, encoding a sperm membrane protein was isolated from a rat testis cDNA expression library. Using the RSD-2 insert in combination with rapid amplification of cDNA ends (RACE), the corresponding human gene was isolated from a human testis cDNA expression library. The human testis cDNA, HSD-2, is 3654 bp in length and contains an open reading frame of 763 codons. Hydropathicity analysis showed that the deduced polypeptide is a single strand transmembrane protein. The deduced polypeptide has partial homology with the amyloid precursor protein (APP) and high homology with the amyloid precursor homologue, APLP2/APPH. The YWK-II gene was mapped and assigned to human chromosome locus: 11q24-25. Northern blotting of various human tissue RNAs using the HSD-2 cDNA as a probe showed that the gene is transcribed ubiquitously. The cytoplasmic domain of HSD-2 was expressed in Escherichia coli. In-vitro studies showed that the recombinant polypeptide bound to a GTP-binding protein (G(o)) and was phosphorylated by protein kinase C and cdc2 kinase. In mammalian F11 cells, the recombinant polypeptide was found to be coupled to G(o). Thus, the YWK-II component has the characteristics of a G(o)-coupled receptor and may be involved in G(o)-mediated signal transduction pathway. Protein kinase C and cdc2 kinase may regulate this pathway in spermatozoa by phosphorylating the cytoplasmic domain of the YWK-II component.

[P15(INK4B) gene methylation in malignant hematopoietic diseases]

OBJECTIVE

To study the effect of operative region hypermethylation gene in human malignant hematopoietic tumors.

METHODS

The abnormal methylation rate of P(15)(INK4B) gene 5'CpG island in 68 cases of malignant hematopoietic tumor samples were determined by methylation specific PCR using bisulfite modified DNA.

RESULTS

The methylation rates of P(15)(INK4B) were 84%, 0, 50% and 75%, respectively, for 25 cases of acute myeloid leukemia (AML), 15 chronic myeloid leukemia (CML), 16 myelodysplastic syndrome (MDS) and 12 multiple myeloma (MM). P(15)(INK4B) gene was frequently methylated in patients with high risk MDS and early stage of MM.

CONCLUSION

Hypermethylation of P(15)(INK4B) gene is one of the main causes of its inactivation. Hypermethylation of CpG island was closely related to the development of malignant hematopoietic diseases.

Evaluation of D-methionine as a cytoprotectant in cisplatin treatment of an animal model for ovarian cancer

BACKGROUND

To evaluate the use of D-methionine(D-met) as a cytoprotectant in the context of clinically relevant doses of cisplatin.

MATERIALS AND METHODS

Forty five Fischer rats were injected intraperitoneally with 10(6) NuTu-19 cells and treated as follows: group 1 was the control group and received no treatment, group 2 received cisplatin 4 mg/kg and group 3 received cisplatin 4 mg/kg plus D-met. There were two groups that received high dose cisplatin. Group 4 received cisplatin 8 mg/kg and group 5 received cisplatin 8 mg/kg plus D-met. Treatment was initiated four weeks after injection of the NuTu-19 cells, and consisted of four weekly intraperitoneal injections. Serum BUN and creatinine levels in the high dose groups evaluated nephrotoxicity and clinical outcome was measured by mean survival using Kaplan Meier analysis.

RESULTS

There were no significant elevations in serum BUN or creatinine levels in any of the rats treated with high dose cisplatin. In the animals given cisplatin 8 mg/kg plus D-met, death from toxicity was prevented and all animals completed four treatments. In contrast, only two animals in group 4 (cisplatin 8 mg/kg alone) completed 4 treatments. There was a significant improvement in survival for the animals given D-met. (p = .0001) In all treated groups except for group 4, there was an improvement in survival compared to the control group. When comparing groups 2 and 3 (4 mg/kg +/- D-met), there was a subjective decrease in tumor response for group 3 but mean survival was not statistically different. (91 vs. 81 days; p = 0.07) A comparison of groups 2 and 5 revealed no survival benefit using high dose cisplatin with D-met. (91 vs. 79 days; p = 0.10).

CONCLUSIONS

Our results indicate that D-methionine provides cytoprotection against cisplatin toxicity without significant compromise of antitumor activity. All though D-methionine allowed for significant dose intensification of cisplatin above standard doses, there was no survival advantage noted in this group of animals. The indications for its use in the treatment of ovarian cancer remain to be determined.

Accumulation of p53 in infectious mononucleosis tissues

Epstein-Barr virus (EBV) infects lymphocytes, where it persists indefinitely for the life of the host; whether the virus interacts with p53 to maintain itself in these cells is unknown. Lymphoid biopsy samples from 10 patients with infectious mononucleosis (IM) were examined for expression of p53 by immunohistochemistry. Accumulation of p53 was detected in all 10 cases, primarily in large lymphocytes of the expanded paracortex. The presence of EBV was confirmed in all 10 cases by EBER1 (EBV-encoded RNA) in situ hybridization, whereas 11 non-IM control samples lacked significant EBER1 and did not express p53 in paracortical lymphocytes. Interestingly, EBV infection alone does not cause accumulation of intracellular p53, because many more cells expressed EBER1 than p53 in the IM tissues. To determine whether p53 was confined to the subset of infected cells in which viral replication was occurring, BZLF1 immunostains were performed. Viral BZLF1 was detected in 8 of 10 IM tissues; however, the paucity and small size of the BZLF1-expressing lymphocytes suggests that they are not the same cells overexpressing p53. To further examine the relationship between p53 and EBV gene expression, the tissues were studied for latent membrane protein 1 (LMP1) expression by immunohistochemistry. Viral LMP1 was observed in the large paracortical lymphocytes of all 10 cases of IM, indicating co-localization of p53 and LMP1 in these cells. Our findings confirm that p53 overexpression is not specific for nodal malignancy and that p53 accumulation is characteristic of IM. Because p53 was not coexpressed in the same cells as BZLF1, it appears that BZLF1 is not directly responsible for p53 accumulation. Nevertheless, co-localization of p53 and LMP1 in activated-appearing lymphocytes suggests that EBV infection is responsible for p53 accumulation. HUM PATHOL 31:1397-1403.

Changing the donor cofactor of bovine alpha 1, 3-galactosyltransferase by fusion with UDP-galactose 4-epimerase. More efficient biocatalysis for synthesis of alpha-Gal epitopes

Two fusion enzymes consisting of uridine diphosphogalactose 4-epimerase (UDP-galactose 4-epimerase, EC ) and alpha1, 3-galactosyltransferase (EC ) with an N-terminal His(6) tag and an intervening three-glycine linker were constructed by in-frame fusion of the Escherichia coli galE gene either to the 3' terminus (f1) or to the 5' terminus (f2) of a truncated bovine alpha1, 3-galactosyltransferase gene, respectively. Both fusion proteins were expressed in cell lysate as active, soluble forms as well as in inclusion bodies as improperly folded proteins. Both f1 and f2 were determined to be homodimers, based on a single band observed at about 67 kDa in SDS-polyacrylamide gel electrophoresis and on a single peak with a molecular mass around 140 kDa determined by gel filtration chromatography for each of the enzymes. Without altering the acceptor specificity of the transferase, the fusion with the epimerase changed the donor requirement of alpha1, 3-galactosyltransferase from UDP-galactose to UDP-glucose and decreased the cost for the synthesis of biomedically important Galalpha1,3Gal-terminated oligosaccharides by more than 40-fold. For enzymatic synthesis of Galalpha1,3Galbeta1,4Glc from UDP-glucose and lactose, the genetically fused enzymes f1 and f2 exhibited kinetic advantages with overall reaction rates that were 300 and 50%, respectively, higher than that of the system containing equal amounts of epimerase and galactosyltransferase. These results indicated that the active sites of the epimerase and the transferase in fusion enzymes were in proximity. The kinetic parameters suggested a random mechanism for the substrate binding of the alpha1, 3-galactosyltransferase. This work demonstrated a general approach that fusion of a glycosyltransferase with an epimerase can change the required but expensive sugar nucleotide to a less expensive one.

Optically defined multifunctional patterning of photosensitive thin-film silica mesophases

Photosensitive films incorporating molecular photoacid generators compartmentalized within a silica-surfactant mesophase were prepared by an evaporation-induced self-assembly process. Ultraviolet exposure promoted localized acid-catalyzed siloxane condensation, which can be used for selective etching of unexposed regions; for "gray-scale" patterning of refractive index, pore size, surface area, and wetting behavior; and for optically defining a mesophase transformation (from hexagonal to tetragonal) within the film. The ability to optically define and continuously control both structure and function on the macro- and mesoscales is of interest for sensor arrays, nanoreactors, photonic and fluidic devices, and low-dielectric-constant films.

Molecular cloning and functional analysis of three type D endogenous retroviruses of sheep reveal a different cell tropism from that of the highly related exogenous jaagsiekte sheep retrovirus

Integrated into the sheep genome are 15 to 20 copies of type D endogenous loci that are highly related to two exogenous oncogenic viruses, jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV). The exogenous viruses cause infectious neoplasms of the respiratory tract in small ruminants. In this study, we molecularly cloned three intact type D endogenous retroviruses of sheep (enJS56A1, enJS5F16, and enJS59A1; collectively called enJRSVs) and analyzed their genomic structures, their phylogenies with respect to their exogenous counterparts, their capacity to form viral particles, and the expression specificities of their long terminal repeats (LTRs). In addition, the pattern of expression of enJSRVs in vivo was studied by in situ hybridization. All of the three enJSRV proviruses had open reading frames for at least one of the structural genes. In particular, enJS56A1 had open reading frames for all structural genes, but it could not assemble viral particles when highly expressed in human 293T cells. We localized the defect for viral assembly in the first two-thirds of the gag gene by making a series of chimeras between enJS56A1 and the exogenous infectious molecular clone JSRV(21). Phylogenetic analysis distinguished five ovine type D retroviruses: enJSRV groups A and B, ENTV, and two exogenous JSRV groups (African versus United Kingdom/North America isolates). Transient transfection assays indicated that the LTRs of the three enJSRVs were not preferentially active in differentiated lung epithelial cells. This suggests that the pulmonary tropic JSRV developed from a type D retrovirus that did not have lung specificity. Consistent with this, in situ hybridization of a panel of normal ovine tissues revealed high expression of enJSRV mRNA in the luminal epithelium and glandular epithelium of the uterus; lower expression was localized in the lamina propria of the gut and in the bronchiolar epithelium of the lungs.

In vivo genomic footprinting of the human T-cell leukemia virus type 1 (HTLV-1) long terminal repeat enhancer sequences in HTLV-1-infected human T-cell lines with different levels of Tax I activity

The Tax protein of human T-cell leukemia virus type 1 (HTLV-1) enhances viral gene expression through sequences in the U3 region of the viral long terminal repeat. These sequences consist of three imperfect 21-bp repeats (TRE-1s) and a region between the promoter-central and promoter-proximal 21-bp repeats (TRE-2). The TRE-1s contain a core cyclic AMP response element (CRE) motif and can be bound by CREB, ATF-1, ATF-2, and other members of the CREB-ATF superfamily of transcription factors. Tax enhances CREB binding to TRE-1 in vitro, and it promotes dimerization of CREB as well as other bZIP proteins. Using ligation-mediated PCR on in vivo dimethyl sulfate-treated HTLV-1-infected cell lines MT-2 and MT-4, we have compiled a profile of protein occupancy in the HTLV-1 enhancer sequences in the presence of high (MT-2) and low (MT-4) levels of biologically active Tax I. The in vivo footprinting showed that all three TRE-1s were bound by protein(s), but only in MT-2 cells. In MT-2 cells, all TRE-1s showed strong protection of the G residues in the central CRE, and the footprints extended to differing degrees into the GC-rich flanking sequences. This indicated Tax I-dependent loading of transcription factors onto the HTLV-1 TRE-1s in vivo. In vivo footprinting on TRE-2 indicated that this region was bound by proteins regardless of the Tax I status of the cell line. However, the presence of Tax I increased the extent and altered the profile of proteins binding TRE-2 in vivo.

Moloney murine leukemia virus-induced tumors show altered levels of proapoptotic and antiapoptotic proteins

Moloney murine leukemia virus (M-MuLV) is a replication-competent, simple retrovirus that induces T-cell lymphomas when inoculated into neonatal mice. The tumor cells are typically derived from immature T cells. During preleukemic times, a marked decrease in thymic size is apparent in M-MuLV-inoculated mice. We previously demonstrated that this thymic regression is correlated with enhanced levels of thymocyte apoptosis (C. Bonzon and H. Fan, J. Virol. 73:2434-2441, 1999). In this study, we investigated the apoptotic state of M-MuLV-induced tumors. M-MuLV-induced tumors were screened for expression of the apoptotic proteins Fas and Bcl-2 by three-color flow cytometric analysis. Single-positive (SP; CD4(+) CD8(-) and CD4(-) CD8(+)) tumor cells generally displayed lower cell surface expression of Fas than SP thymocytes from uninoculated control mice. Double-positive (DP; CD4(+) CD8(+)) M-MuLV-induced tumor cells fell into two categories: those with normal high levels of Fas and those with low levels of Fas. Additionally, the vast majority of DP tumors showed elevated Bcl-2 levels. The DP tumor cells retaining normal/high Fas expression were capable of transducing an apoptotic signal upon anti-Fas engagement. In addition, DP and CD4(+) SP tumor populations displayed higher levels of Fas ligand than normal thymocytes with the same phenotypes. In contrast, CD8(+) SP and CD4(-) CD8(-) tumors did not show elevated Fas ligand expression. There was no significant correlation between Fas and Fas ligand expression in the DP tumors, suggesting that Fas Ligand expression was not the driving force behind Fas down-regulation. These results suggest that both the Fas death receptor and mitochondrial pathways of apoptotic death are active in M-MuLV-induced tumors and that they must be modulated to permit cell survival and tumor outgrowth.

Evidence for migration of donor bone marrow stromal cells into recipient thymus after bone marrow transplantation plus bone grafts: A role of stromal cells in positive selection

Intrathymic T-cell differentiation is characterized by two selection events: positive and negative selection. It has been shown that thymic epithelial cells in the cortex are involved in the positive selection, while macrophages and dendritic cells, derived from hemopoietic stem cells, are involved in the negative selection. Here we investigate whether donor-derived bone marrow stromal cells can migrate into the thymus and participate there in positive selection after bone marrow transplantation plus bone grafts (to recruit bone marrow stromal cells). Allogeneic bone marrow transplantation with or without bone grafts was carried out in the [C57BL/6-->C3H] combination. Fluorescence-activated cell sorter analyses of recipient thymic adherent cells showed that donor-type bone marrow stromal cells exist in the thymus of mice that received bone marrow plus bone grafts but not in the mice that received bone marrow cells alone. Histological examination using confocal microscopy also confirmed the existence of donor-type stromal cells in the thymus of mice that received bone marrow cells plus bones. Both T-cell proliferation and plaque-forming cell assays indicated that the T cells of such mice show donor-type major histocompatibility complex-restriction. These findings strongly suggest that stromal cells can migrate from the bone marrow to the thymus, where they participate in the positive selection of thymocytes.

Roles of cysteines in rat dipeptidyl peptidase IV/CD26 in processing and proteolytic activity

The multifunctional type II transmembrane glycoprotein, dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5), is expressed by almost all mammalian cells and is identical to the adenosine deaminase binding protein CD26 on lymphocytes. The extracellular part of rat DPPIV can be divided into three domains the middle part of which harbors 10 of the 12 highly conserved cysteine residues. The cysteine-rich domain is responsible for DPPIV-binding to collagen I and to extracellular ADA. The participation of distinct cysteines in disulfide bridges is not yet known. Titration experiments have shown the presence of six free cysteines and three disulfide bridges in native rat DPPIV. To investigate the role of distinct cysteines in the structure-function relationships of rat DPPIV we constructed 12 different cysteine point mutations (C299, C326, C383, C455, C650 mutated to G; C337, C395, C445, C448, C473, C552, C763 mutated to S). Intracellular translocation to the cell surface of stable transfected Chinese hamster ovary cells was examined with antibodies against different epitopes of DPPIV. Surface expression of mutants C326G, C445S and C448S is inhibited totally; mutants C337S, C455G, C473S and C552S show weak expression only. In parallel, the half-life of these mutants is reduced to < 10% compared with wild-type enzyme. We were able to show that the specific peptidase activity of the mutant protein depends on cell-surface expression, dimerization and the existence of a 150-kDa form demonstrable by nondenaturing SDS/PAGE. We conclude that cysteine residues 326, 337, 445, 448, 455, 473 and 552 in rat DPPIV are essential for the correct folding and intracellular trafficking of this glycoprotein, and therefore for its normal biological properties.

[Study of polyaluminium ferric chloride (PAFC) aqueous solutions visible spectra: the relationship among their absorbance at 460 nm, basicities and total Fe(III) concentration of PAFC solutions]

The visible spectra of forty-five synthesized polyaluminium ferric chloride (PAFC) aqueous solutions with different [OH]/[Al + Fe] (B) and nAl/nFe(molar ratio) were investigated. The results showed that their absorbances A of shoulder at 460 nm are all linear interrelationship with their B. We made the curve of absorbance A of PAFC with same B vs. nAl/nFe, there was a turning point. All of these points just located at the places of pH value rising higher in pH- nAl/nFe diagrams. For these reason, we thought that these points stand for the dynamic equilibrium of OH- between the polynucleus hydroxyl Fe(III) and Al(III). These points made certain relationship among the absorbance A at 460 nm, basicities and total Fe(III) concentration of PAFC solutions.

The long terminal repeat of Jaagsiekte sheep retrovirus is preferentially active in differentiated epithelial cells of the lungs

Jaagsiekte sheep retrovirus (JSRV) is the etiologic agent of a contagious bronchioloalveolar carcinoma of sheep known as sheep pulmonary adenomatosis (SPA; ovine pulmonary carcinoma). JSRV is unique among retroviruses because it transforms the alveolar type II cells and the nonciliated bronchiolar cells (Clara cells) of the lungs; these cells are where JSRV is specifically expressed in both naturally and experimentally SPA-affected sheep. In this study, we investigated the cell specificity of JSRV expression. By transient-transfection assays of 23 different cell lines with a reporter plasmid driven by the JSRV long terminal repeat (LTR), pJS21-luc, we found that the JSRV LTR is preferentially active in cell lines derived from type II pneumocytes and Clara cells (MLE-15 and mtCC1-2 mouse cell lines). Reporter assays using progressive 5' deletions of pJS21-luc allowed us to establish that the JSRV enhancers are able to activate the JSRV proximal promoter in MLE-15 and mtCC1-2 cells, but they have very low activity in mouse cells of other lineages (e.g., NIH 3T3). The JSRV enhancers are able to activate heterologous promoters in both MLE-15 and 3T3 cells, although optimal activity is achieved in MLE-15 cells only with the homologous JSRV promoter. Thus, JSRV cell-specific LTR activity appears to result from an interaction between the enhancer elements and the JSRV proximal promoter elements. By mutation analysis, we established that an upstream NF-kappaB-like element appears to be responsible for approximately 50% of the JSRV LTR transcriptional activity in MLE-15 cells. Electrophoretic mobility shift assays showed evidence of a factor(s) that binds to this sequence. Antibody supershift experiments indicated that the factor(s) is not related to NF-kappaB component p50 or p52. This factor also appeared to be present in cells that do not support a high level of JSRV expression. Finally the JSRV(21) LTR contains putative enhancer binding motifs for transcription factors such as hepatocyte nuclear factor 3 (HNF-3) that are involved in lung-specific gene expression. Cotransfection experiments demonstrated that exogenous HNF-3 is able to enhance the expression of pJS21-luc in NIH 3T3 cells, which normally show minimal enhancer activity for the JSRV LTR.