Multiplexed molecular interactions of nuclear receptors using fluorescent microspheres.

BACKGROUND: We describe a novel microsphere-based system to identify and characterize multiplexed interactions of nuclear receptors with peptides that represent the LXXLL binding region of coactivator proteins. METHODS: In this system, individual microsphere populations with unique red and orange fluorescent profiles are coupled to specific coactivator peptides. The coactivator peptide-coupled microsphere populations are combined and incubated with a nuclear receptor that has been coupled to a green fluorochrome. Flow cytometric analysis of the microspheres simultaneously decodes each population and detects the binding of receptor to respective coactivator peptides by the acquisition of green fluorescence. RESULTS: We have used this system to determine the binding affinities of human estrogen receptor beta ligand binding domain (ERbeta LBD) and human peroxisome proliferator activated receptor gamma ligand binding domain (PPARgamma LBD) to a set of 34 coactivator peptides. Binding of ERbeta LBD to a coactivator peptide sequence containing the second LXXLL motif of steroid receptor coactivator-1 (SRC-1(2) (676-700) is shown to be specific and saturable. Analysis of receptor binding to a multiplexed set of coactivator peptides shows PPARgamma LBD binds with high affinity to cAMP response element binding protein (CBP) peptides and to the related P300 peptide while ERbeta LBD exibits little binding to these peptides. Using the microsphere-based assay we demonstrate that ERbeta LBD and PPARgamma LBD binding affinities for the coactivator peptides are increased in the presence of agonist (estradiol or GW1929, respectively) and that ERbeta LBD binding is decreased in the presence of antagonist (raloxifene or tamoxifen). CONCLUSIONS: This unique microsphere-based system is a sensitive and efficient method to simultaneously evaluate many receptor-coactivator interactions in a single assay volume. In addition, the system offers a powerful approach to study small molecule modulation of nuclear receptor binding.

Characterization of human E4BP4, a phosphorylated bZIP factor.

In this report we described the isolation of transcription factor E4BP4 by lambda gt11 expression cloning using a probe containing the CRE/ATF-like sequence located between -2764 bp and -2753 bp in the upstream regulatory region for the human IL-1 beta gene. DNaseI protection, gel mobility shift analysis, and cotransfection studies were performed to investigate the binding and functional properties of E4BP4 using IL-1 beta promoter sequences. By DNaseI footprinting, a protection pattern was generated over the CRE/ATF-like site and the flanking sequences by bacterially produced E4BP4. Competition experiment by gel shift assay indicated that E4BP4 bound specifically to CRE/ATF-like site, not NF kappa B-like site. In cotransfection studies, E4BP4 repressed promoter activity and this repression was mediated through the CRE/ATF-like site. Mutational analysis of E4BP4 suggested that the DNA binding as well as repression activities required leucine heptad repeat domain. Analysis of E4BP4 produced in Escherichia coli and Sf9 cells infected with recombinant baculovirus indicated that baculovirus produced protein showed enhanced binding to the CRE/ATF-like site compared to the E. coli-produced protein. Analysis of posttranslational modifications indicated that E4BP4 produced in Sf9 cells was phosphorylated and this phosphorylation was important for the DNA binding activity of E4BP4.

Cyclic AMP signaling pathways are important in IL-1 beta transcriptional regulation.

An intact cAMP response element (CRE) in the upstream regulatory sequence of IL-1 beta (-2755/-2762) has been shown to be essential for maintaining full IL-1 beta inducibility following treatment with LPS, PMA, or TNF-alpha. In the present study, using the recombinant plasmid pIL-1(4.0 kb)-chloramphenicol acetyltransferase, containing 4.0 kb of the IL-1 beta upstream regulatory sequence, we have demonstrated that dibutyryl cAMP treatment alone is capable of induction. Due to the critical nature of the CRE for the induction of IL-1 beta transcription, an effort was made to determine the importance of the cAMP signaling pathway(s) by determining whether CRE binding protein (CREB) and other CREB/activating transcription factor (ATF) family members that responded to cAMP were associated with the DNA-protein complex that forms at this site. Nuclear extracts prepared from LPS-treated THP-1 5A cells were fractionated by ammonium sulfate precipitation and heparin-Sepharose chromatography, and the resulting fractions were characterized in electrophoretic gel mobility shift assays. These purification steps resulted in an approximately 100-fold enrichment of the proteins binding to the CRE site. Western blot analysis of isolated fractions, using CREB- and ATF-1-specific Ab showed an increased level of these proteins in the enriched fractions. Tryptic digest and DNase I protection studies showed the presence of CREB protein in the complex at the CRE site. Supershift electrophoretic gel mobility shift assays and immunoprecipitation analysis provided further evidence that both CREB and ATF-1 are present in the complex. In addition, an increase in CREB phosphorylation was observed when THP-1 5A cells were treated with dibutyryl cAMP, LPS, or both. These studies confirm the importance of a cAMP signaling pathway(s) in the regulation of IL-1 beta at the transcriptional level.

A cyclic adenosine 3',5'-monophosphate signal is required for the induction of IL-1 beta by TNF-alpha in human monocytes.

IL-1 beta is a cytokine generally considered to be a major component involved in the pathogenesis of rheumatoid arthritis and other inflammatory diseases. Of the agents found in high concentrations in inflamed rheumatoid arthritis joints, TNF-alpha is among the most strongly implicated as an in vivo inducer of IL-1 beta. Here we report that in human PBMC and in a stable transfectant of the promonocytic cell line, THP-1, TNF-alpha indeed appears to be an inducer of IL-1 beta production, but only in the presence of dibutyryl cAMP or agents such as the PG that elevate intracellular cAMP levels. This TNF-alpha/cAMP pathway regulates IL-1 beta production at the level of transcription and requires a cAMP response element located between -2762 and -2755 bp in the upstream regulatory sequence of IL-1 beta. Because PG, which are known to elevate cAMP levels in vivo, and TNF-alpha are both found in significant quantities in the synovial fluid of rheumatoid arthritis joints, the observed synergistic up-regulation in IL-1 beta synthesis by TNF-alpha/cAMP (PG) may provide valuable insight into the potential pathways involved in the continuous production of IL-1 beta in the chronically inflamed joint.

NF-kappa B regulates IL-1 beta transcription through a consensus NF-kappa B binding site and a nonconsensus CRE-like site.

In these studies, we show that NF-kappa B induces transcription from the human pro-IL-1 beta (IL-1 beta) gene. A recombinant plasmid pIL-1(-4000)-CAT, containing 4 kb of the IL-1 beta gene upstream regulatory sequence was transactivated by the p65 subunit of NF-kappa B or by treatment of the cells with a combination of NF-kappa B inducers including LPS, PMA, and dibutyryl cyclic AMP (L+P+C) in U937 cells. Coexpression of p65 with L+P+C treatment led to a synergistic response, whereas coexpression of the I kappa B alpha/MAD-3 protein, in place of p65, blocked L+P+C induction. A series of 5' deletion mutants of the IL-1 beta promoter were used to define two p65 response regions: region I located between -2800 to -2720 bp and region II located between -512 and -133 bp. Electrophoretic mobility shift assays confirmed that NF-kappa B-like proteins could bind to two consensus binding sites in region II. A site-specific mutation in only one of these NF-kappa B sites (-296/-286 bp) caused a specific loss of induction by p65 or L+P+C. A cyclic AMP response element (CRE) site (-2761/-2753 bp) in region I has been shown previously to be critical for L+P+C induction. Mutation of the CRE in an enhancerless test plasmid containing two copies of region I blocked transactivation by p65. Likewise, coexpression of I kappa B alpha inhibited CRE-dependent L+P+C induction of the wild-type counterpart. These data show that NF-kappa B regulates a nonconsensus CRE site in addition to the consensus binding site at -296/-286 bp and suggest that NF-kappa B may play multiple roles in the induction of IL-1 beta transcription.

A CRE/ATF-like site in the upstream regulatory sequence of the human interleukin 1 beta gene is necessary for induction in U937 and THP-1 monocytic cell lines.

Transfection of U937 and THP-1 cells with a recombinant plasmid, pIL1(4.0kb)-CAT, containing 4 kb of the interleukin 1 beta (IL-1 beta) gene upstream regulatory sequence resulted in inducer-dependent expression of chloramphenicol acetyltransferase activity. Treatment of the transfected cells with various combinations of the inducers lipopolysaccharide, phorbol myristate acetate, and dibutyryl cyclic AMP upregulated the IL-1 beta promoter. In U937 and THP-1 cells, maximum stimulation of both the endogenous IL-1 beta gene and pIL1(4.0kb)-CAT transfectants was observed following treatment with the combination of inducing agents lipopolysaccharide-phorbol myristate acetate-dibutyryl cyclic AMP. This combination of inducing agents was used to identify and study, at the molecular level, some of the regulatory elements necessary for induction of the IL-1 beta gene. A series of 5' deletion derivatives of the upstream regulatory sequence were used in transient transfection assays to identify an 80-bp fragment located between -2720 and -2800 bp upstream of the mRNA start site that was required for induction. Exonuclease III mapping, electrophoretic mobility shift assays (EMSA), and DNA sequence analysis of this region were used to identify a transcription factor binding sequence which contained a potential cyclic AMP response element (CRE/ATF)- and NF-kappa B-like binding site. Site-directed mutagenesis of the CRE/ATF-like site resulted in the loss of binding of a specific factor or factors as determined by EMSA. The loss of binding activity directly correlated with a loss of approximately 75% of promoter activity as determined in transient transfection assays. As determined by EMSA, the factor binding to the CRE/ATF-like site was present in nuclear extracts prepared from both uninduced and induced THP-1 and U937 cells. However, the intensity of the band appeared to be increased when nuclear extracts from induced cells were used. In contrast to the CRE/ATF mutation, which resulted in the loss of promoter activity, mutation of the NF-kappa B-like site resulted in a moderate increase in activity in U937 cells. A similar increase in promoter activity was not observed in THP-1 cells. From these studies, we conclude that a CRE/ATF-like site and a factor or factors interacting with this site are essential for the maximum induction of the IL-1 beta gene in stimulated U937 and THP-1 cells.

Large-scale purification of plasmid DNA by fast protein liquid chromatography using a Hi-Load Q Sepharose column.

The large-scale purification of plasmid DNA was achieved using fast protein liquid chromatography on a Hi-Load Q Sepharose column. This method allows for the purification of plasmids starting from crude plasmid DNA, prepared by a simple alkaline lysis procedure, to pure DNA in less than 5 h. In contrast to the previously described plasmid purification methods of CsCl gradient centrifugation or high-pressure liquid chromatography, this method does not require the use of any hazardous or expensive chemicals. More than 100 plasmids varying in size from 3 to 15 kb have been purified using this procedure. A Mono Q Sepharose column was initially used to purify plasmids smaller than 8.0 kb; however, a Hi-Load Q Sepharose column proved more effective with plasmids larger than 8 kb. The loading of plasmids larger than 8 kb on the Mono Q column resulted in a high back pressure and the plasmid DNA could not be eluted from the column. Thus, for routine purification we utilize the Hi-Load Q Sepharose column. Plasmids purified by this method had purity, yield, and transfection efficiency in mammalian cells similar to those of plasmids purified by CsCl density gradient centrifugation.

Three-dimensional imaging for brachytherapy planning.

A computerized 3-D brachytherapy treatment planning program has been developed which simulates catheter trajectories, radioisotope seed positioning and percentage dosimetry zones about a catheter/seed array in relationship to CT or MRI images. The high activity 125I seed is used in this program. A visual and a non-linear mathematical optimization program will also be described.

Three-dimensional whole-brain mapping.

The implementation and use of a computerized whole-brain mapping system which can be used in conjunction with MRI, CT, angiographic and other brain imaging techniques is described. Three mapping systems based upon common reference structures about the third and fourth ventricular core of the brain are used in conjunction with internationally recognized nomenclature to create a normalized whole-brain mapping system according to the Talairach/Tournoux proportional grid technique.

Magnetic resonance imaging and anatomic atlas mapping for thalamotomy.

A computerized anatomic atlas mapping technique has been developed and used to determine target sites for stereotactic thalamotomies. The digitized stereotactic atlases of Schaltenbrand and Bailey, Van Buren and Borke, and Schaltenbrand and Wahren are used in conjunction with an associated electrophysiological data base to determine the intended target site on MR images of the diencephalon. This mapping technique uses the 'Brierley and Beck' proportional hypothesis for thalamic nuclear determination. Target site determination by this method was found to be very accurate, and frequently the mere placement of the probe in the target site resulted in tremor cessation.

Human immunodeficiency virus infection and syncytium formation in HeLa cells expressing glycophospholipid-anchored CD4.

The CD4 molecule, a glycoprotein expressed primarily on the cell surface of specific T lymphocytes, is thought to function in T-cell antigen recognition and activation. In addition, CD4 serves as a receptor for human immunodeficiency virus type 1 (HIV-1) by a direct interaction with the HIV-1 surface glycoprotein (gp120). To further characterize the HIV-1-cell interaction, a HeLa cell line was established that expressed a chimeric molecule of CD4 and decay-accelerating factor (DAF). In the chimeric CD4-DAF molecule the transmembrane and cytoplasmic domains of CD4 were deleted and replaced with the carboxy-terminal 37 amino acids of DAF. This resulted in the anchoring of the extracellular domain of CD4 to the cell membrane via a glycophospholipid linkage. The glycophospholipid-anchored CD4 had a molecular size of approximately 56 to 62 kDa and was released following treatment of the cells with phosphatidylinositol-specific phospholipase C. HeLa cells expressing the CD4-DAF hybrid could be infected with HIV-1, as evidenced by reverse transcriptase activity, p24 core antigen content, and infectious virus production. In addition, transfection of the HeLa CD4-DAF cells with a plasmid that directs the synthesis of HIV-1 envelope glycoproteins or cocultivation with HeLa cells expressing the virus glycoproteins resulted in syncytium formation. These results indicate that the transmembrane and cytoplasmic domains of the CD4 molecule are dispensable for both HIV infection and syncytium formation.

A new breast screening programme--an audit of the first year.

The experience of a new breast screening unit is reported. In the first 12 months there was a 72.1% response rate with 9890 women being screened. After the initial screen 598 (5.8%) were referred to the Assessment clinic. Following repeated mammography and clinical examination 166 patients were referred for a surgical opinion; 105 (1.06% of the total screened) were considered to be possibly malignant; 61 further patients with clinical and mammographically benign disease were kept under review by a single surgeon; 101 patients had excision biopsies; 28 of 32 palpable breast lumps and 36 of 69 non-palpable lesions proved to be malignant.

Stomal adenocarcinoma in Crohn's disease.

Malignant change occurring at the site of a stoma in two patients with proved Crohn's disease is described. Patients with ulcerative colitis have an increased risk of colonic malignancy and Crohn's disease is also associated with both small and large bowel carcinoma. Most previous reports of stomal carcinoma have been associated with ulcerative colitis although Crohn's disease seems to carry a greater risk of associated small bowel carcinomas. This is the first report of stomal carcinoma complicating Crohn's disease. Epithelial dysplasia is associated with gastrointestinal carcinomas in both ulcerative colitis and Crohn's disease and a dysplasia-carcinoma sequence has been suggested as the origin of these tumours. In both our patients with stomal adenocarcinoma, dysplasia was identified in adjacent tissues, which suggests a similar mechanism. Malignant change should be suspected if epithelial dysplasia is discovered in a biopsy specimen from the mucosa of an ileostomy in Crohn's disease, and this risk is increased if the dysplasia is of a high grade.

Efficacy of tamoxifen as the primary treatment of operable breast cancer in the high risk patient.

An audit of 43 breast cancer patients, considered to be of high operative risk and treated only with Tamoxifen was performed. All cases were potentially operable. Good outcome was obtained in only one-third of patients. Salvage surgery had no operative mortality.

Aspiration cytology and ultrasonography of cold thyroid nodules.

Over an 18 month period, 50 'high risk' patients with solitary or dominant cold thyroid nodules on 99m Tc-pertechnetate scanning, have undergone fine needle aspiration biopsy cytology (ABC) under general anaesthetic prior to thyroidectomy. Histological malignancy was confirmed in only four patients (8%). Cytological malignancy was suspected or confirmed in six patients, each having a false positive rate of 4%. There were no false negative reports. Ultrasonography, performed pre-operatively in 37 of the patients, did not significantly add to the overall patient management. ABC appears to be safe, simple and sufficiently accurate to incorporate its use routinely in the pre-operative assessment of thyroid nodules.

An Alcaligenes faecalis isolate from turkeys: pathogenicity in selected avian and mammalian species.

An Alcaligenes faecalis isolate of known pathogenicity for turkeys was examined for adherence and cytotoxicity in tracheal organ cultures of turkeys, chickens, Japanese quail, guinea pigs, hamsters, and mice, and for colonization and pathogenicity in these 6 species. Adherence and colonization were detected by fluorescent antibody staining. Infected and noninfected tracheal rings were examined by phase-contrast microscopy for cytotoxicity (ciliostasis, blebing of the cell membrane, and sloughing of the ciliated epithelium). Alcaligenes faecalis adhered to the tracheal rings of all species examined. Cytotoxicity was apparent in the tracheal rings of turkeys, quail, and chickens. Cytotoxicity was not detected in tracheal rings from the mammalian species. Alcaligenes faecalis colonization of turbinates and tracheas of intact turkeys and quail was detected. Clinical signs of alcaligenes rhinotracheitis were observed and histopathologic characteristics of the disease were detected. Chickens, guinea pigs, hamsters, and mice were refractory to infection with this isolate of A faecalis.