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Y S Lin

Publications and source records attributed to Y S Lin.

At least 163 records · Page 9Linked to original sources
PubMed1989

Identification and purification of a Saccharomyces cerevisiae protein with the DNA binding specificity of mammalian activating transcription factor.

Activating transcription factor (ATF) is a mammalian transcriptional activator, which is involved in the expression of many viral E1a-inducible and cellular cAMP-inducible genes. Here we identify from the yeast Saccharomyces cerevisiae a previously uncharacterized protein whose DNA binding specificity is like mammalian ATF. We purify this protein (yATF) and show that it is a 66-kDa polypeptide. Finally, we demonstrate that a mammalian ATF site can function as an upstream activating sequence in S. cerevisiae. Taken together, our results suggest that yATF is a previously uncharacterized S. cerevisiae transcriptional activator.

Activating Transcription Factors↗
PubMed1988

Transcription factor ATF interacts with the TATA factor to facilitate establishment of a preinitiation complex.

The mammalian activator protein ATF stimulates transcription from the adenovirus E4 promoter by binding to multiple upstream promoter and enhancer elements. DNAase footprint analyses have revealed that there are cooperative interactions between ATF and TFIID (the mammalian TATA factor) when both are bound simultaneously to the promoter and that these interactions in turn facilitate promoter recognition by RNA polymerase II and the general initiation factors TFIIB and TFIIE. However, the complex of TFIID and the other general factors is stable following oligonucleotide-mediated dissociation of ATF from the complete preinitiation complex. These results indicate that TFIID is a direct target for ATF, that these interactions facilitate assembly of a complete preinitiation complex, and that the role of ATF might be transient.

Adenoviridae↗
PubMed1988

GAL4 derivatives function alone and synergistically with mammalian activators in vitro.

We show that derivatives of the yeast transcriptional activator GAL4, synthesized in and purified from E. coli, stimulate transcription of a mammalian gene (the adenovirus E4 gene) in a HeLa cell nuclear extract. Stimulation depended upon GAL4 binding sites inserted in the template. When the GAL4 sites were placed immediately upstream of the E4 TATA box, GAL4 stimulated efficiently. When the GAL4 sites were further upstream from TATA, however, efficient stimulation by GAL4 required, in addition, a site for a mammalian transcriptional activator immediately upstream of TATA. Under these conditions, the GAL4 derivatives functioned synergistically with the proximally bound activator. Previous experiments have defined two "activating regions" in GAL4, and our current experiments define a third, whose function is observed in vitro but not in vivo.

Adenoviruses, Human↗
PubMed1988

Percutaneous mitral balloon dilatation by a new sequential single- and double-balloon technique.

Percutaneous balloon valvotomy by means of a new sequential single- and and double-balloon dilatation procedure was performed in 23 patients (aged 13 to 53 years) with severe rheumatic mitral stenosis. The dilatation procedure was initially performed with a small balloon to primarily dilate the stenotic valve for easier passage of a second balloon catheter and to make the procedure tolerable for severely ill patients; the procedure was then followed by two balloons to further increase the mitral valve area (MVA) for effective dilatation of the stenotic mitral orifice. The dilatation was successful in all patients; the mitral valve pressure gradient decreased from 19 +/ 6 to 5 +/ 2 mm Hg, the cardiac output increased from 4.0 +/ 0.5 to 5.2 +/ 0.6 L/min, and the MVA increased from 0.8 +/ 0.2 to 1.9 +/ 0.4 cm2 (p less than 0.01 each). The MVA after dilatation was relative to the effective balloon dilatation diameter selected (r = 0.57; p less 0.01). A small atrial septal defect was observed in 3 of 23 patients immediately after the dilatation procedure. Mild mitral regurgitation was produced in 3 of 23 patients by the dilatation. We conclude that the sequential single- and double-balloon dilatation procedure can effectively increase the MVA and improve hemodynamics in severe mitral stenosis and that the larger effective balloon diameter of 24.8 mm or more (12 +/ 18 mm of two balloons) is necessary for effective dilatation.

Adult↗
PubMed1988

Interaction of a common cellular transcription factor, ATF, with regulatory elements in both E1a- and cyclic AMP-inducible promoters.

We have previously identified a cellular transcription factor, ATF, which is involved in the expression of multiple adenovirus E1a-inducible genes. Here we show that ATF also binds to regulatory elements in cellular cAMP-inducible promoters. In these cellular promoters, ATF binds to a consensus sequence that has been previously shown to be necessary and in some instances sufficient for cAMP-inducible transcription. Furthermore, we show that binding of ATF to these promoter elements is required for the constitutive in vitro transcriptional activity of the cAMP-inducible somatostatin gene. Taken together, our results suggest that a common cellular transcription factor, ATF, can be regulated in vivo by two apparently unrelated inducing agents: the adenovirus E1a protein and cAMP.

Activating Transcription Factors↗
PubMed1988

Production and characterisation of monoclonal antibodies specific for staphylococcal enterotoxin B.

We have generated monoclonal antibodies (MABs) to staphylococcal enterotoxin B (SEB) in BALB/c mice. Five out of 20 clones which produce anti-SEB MABs have been characterised. Among them, three produce IgG1/kappa, one produces IgM/lambda, and one apparently produces both IgG1/lambda and IgM/lambda MABs. The anti-SEB titres of ascites fluids range from 3200 to greater than 819200 by ELISA. All of the MABs analysed thus far neutralise the mitogenic response of BALB/c splenocytes to a suboptimal dose of SEB. Also, the induction of suppressor cells by SEB in vitro is reversed by pre-incubating SEB with these MABs. Limited digestion with chymotrypsin, trypsin or Staphylococcus aureus V8 protease yields peptide fragments which have been tested by Western-blot analysis. MABs 1FD7 and 2GD9 are specific for the carboxy-terminal end of SEB, and have a similar, but not identical, binding epitope. MABs 2DA3 and 2HA10 bind to intact SEB but not to cleaved products, and are probably specific for antigenic determinants altered by the cleavage or by the denaturing conditions of the electrophoresis, or by both.

Animals↗
PubMed1988

A common trans-acting factor is involved in transcriptional regulation of neurotransmitter genes by cyclic AMP.

Activation of neurotransmitter receptors can regulate transcription in postsynaptic cells through the actions of second messengers. Trans-synaptic regulation of transcription appears to be an important mechanism controlling the synthesis of molecules involved in neuronal signaling, especially neuropeptides. Proenkephalin, vasoactive intestinal polypeptide, and somatostatin have been shown to be transcriptionally regulated by the second messenger, cyclic AMP (cAMP), as has the catecholamine synthesizing enzyme tryosine hydroxylase. cAMP-inducible elements have been mapped within these genes, and trans-acting factors which bind to several such elements have been identified. With the discovery that individual neurons generally contain multiple transmitters within their synaptic terminals, it has become important to understand in detail the mechanisms by which the synthesis of transmitters can be coregulated. Here we compare the structure and function of the proenkephalin cAMP-inducible enhancer with the mapped cAMP-inducible elements of the vasoactive intestinal polypeptide, somatostatin, and tyrosine hydroxylase genes and a putative cAMP-inducible element in the proto-oncogene c-fos. We have previously shown that the proenkephalin enhancer is composed of two different elements, ENKCRE-1 and ENKCRE-2. We show here that one of these, ENKCRE-2, is structurally similar to elements found within the vasoactive intestinal polypeptide, somatostatin, and tyrosine hydroxylase genes and binds a trans-acting factor that is competed for both in cotransfection experiments (in vivo) and in DNase I footprint assays (in vitro) by these other elements. The c-fos element has similar structural requirements to confer transcriptional induction by cAMP but competes less strongly. Protein purified by affinity chromatography with the ENKCRE-2 sequence binds to each of these elements. A second element within the proenkephalin cAMP-inducible enhancer, ENKCRE-1, binds a factor that is not competed for by these other genes and is therefore distinct. This analysis suggests a potential mechanism of transcriptional coregulation of the neuronally expressed genes investigated in this study and also demonstrates that multiple factors are involved in transcriptional activation by cAMP.

Binding, Competitive↗
PubMed1988

Induction of suppressor cells by staphylococcal enterotoxin B: identification of a suppressor cell circuit in the generation of suppressor-effector cells.

We have shown previously that staphylococcal enterotoxin B (SEB) has the capacity to non-specifically inhibit antibody responses in vitro through the induction of a suppressor cell population. In the present studies, an analysis of the cellular dynamics has shown that the generation of Lyt-1-2+ suppressor-effector cells is dependent on the initial activation by SEB of an Lyt-1+2- suppressor-inducer population. Co-culture experiments carried out in vitro suggest that the induction of the suppressor-effector population requires at least two signals: one signal is provided by the suppressor-inducer population, and the second signal is provided by SEB. Studies also show that the in vitro antibody response is suppressed when the suppressor cells are added as late as Day 4 of a 5-day culture. While the suppressor cell population activated early in the antibody response is Lyt-1-2+, depletion studies suggest that the population that acts late in an ongoing response bears the Lyt-1+2+ surface phenotype. The results demonstrate that at least three distinct SEB-induced T-cell populations are capable of participating in the suppression of the antibody response. The relationship between the generation of non-specific suppressor cells and the activation of antigen-specific cell circuits is discussed.

Animals↗
PubMed1986

Inhibition of antibody production from the plasmacytoma cell line MOPC-315 by staphylococcal enterotoxin B-induced T-suppressor cells.

Our previous results have shown that staphylococcal enterotoxin B (SEB) induces a population(s) of T cells which has the capacity to suppress the antibody response of splenocytes in vitro. In the present report we have attempted to investigate the effect of SEB-primed cells on the secretion of antibody by the plasmacytoma cell line MOPC-315. We have found that the secretion of antibody by MOPC-315 is significantly reduced in as little as 24 hr of coculture with the suppressor cells. The suppressive activity is not antigen- or isotype-specific, since the antibody secretion by both MPC-11 and HOPC1 plasmacytomas are also inhibited by the SEB-primed cells. In addition, we have found that the SEB-primed cell population which inhibits the antibody production by the MOPC-315 cell line expresses the Lyt-1+,2- and Thy-1+ cell surface markers. The apparent relationship between the SEB-primed suppressor cell population and the population which inhibits a conventional antibody response is discussed.

Animals↗
PubMed1986

Suppression of cytolytic T-cell activity by staphylococcal enterotoxin B-induced suppressor cells: role of interleukin 2.

We have previously shown that staphylococcal enterotoxin B (SEB) is a potent inducer of suppressor T cells which function to inhibit antibody production in vitro. In the present paper we extend these studies and show that the SEB-induced suppressor cells also inhibit the development of cytotoxic lymphocytes in mixed-lymphocyte reaction (MLR) cultures. Since further analysis also showed that the level of interleukin 2 (IL-2) in cultures of SEB-primed cells was significantly reduced, experiments were carried out to determine the role of IL-2 in the inhibition of cytotoxic cell activity. Attempts to neutralize the suppression by supplementing MLR cocultures with delectinated supernatants from concanavalin A (Con A)-stimulated rat splenocytes were not successful. In addition, MLR cocultures supplemented on Day 0 with 50 units of affinity-purified IL-2 were also suppressed. Further analysis showed that the IL-2 activity in the supplemented MLR cocultures containing suppressor cells were significantly reduced by Day 3. However, repeated supplementation of the MLR cocultures with exogenous IL-2 was successful in achieving (and maintaining) "normal" levels of IL-2. The cytotoxic cell activity in these MLR cocultures remained suppressed. These results suggest that the inhibition of cytotoxic cell activity by SEB-induced suppressor cells is independent of IL-2 levels in the MLR coculture.

Animals↗
PubMedDate not supplied

A reusable and specific protein A-coated piezoelectric biosensor for flow injection immunoassay.

A hydrophilic matrix of periodate-oxidized dextran was used as a double-sided linker to covalently immobilize Staphylococcus aureus protein A (SpA) molecules onto a poly-L-lysine-modified piezoelectric crystal surface to improve their stability, activity, and binding specificity with human immunoglobulin G (IgG) in flow injection assays. The prepared sensing crystals displayed best sensitivity and reusability at a flow rate of 140 microL/min. A human IgG concentration as low as 0.3 nM can be detected by this system. Up to 19 successive assay repetitions were achieved without significant loss of sensitivity using the same crystal. The analysis of adsorption kinetics indicates that such a preparation can greatly increase the amount of available active human IgG binding sites on immobilized SpA. Hardly any response arising from unspecific binding was detected. In addition, the sensing crystal prepared by this method was found to retain activity better than one prepared via direct deposition when stored in either wet or dry states. Finally, the prepared SpA-coated crystals were applied to the affinity immobilization of polyclonal goat anti-Schistosoma japonicum glutathione-S-transferase (GST) and were able to subsequently detect GST and its genetically engineered mutant either in a purified form or in the crude cell lysate.

Animals↗
PubMedDate not supplied

New phenanthridine linkers for the solid-phase synthesis of acid-containing compounds.

Two novel, reusable phenanthridine linkers that use cerium ammonium nitrate as a cleavage reagent are described. These linkers are based on a disubstituted amide and are designed for the release of carboxylic acids but tolerate exposure to acidic, basic, and reductive reaction conditions. Application of these linkers to solid-phase organic synthesis affords products in excellent yields and high purities.

Journal Article↗
PubMedDate not supplied

Variability of albumin adducts of 1,4-benzoquinone, a toxic metabolite of benzene, in human volunteers.

A putative haematotoxic and leukaemogenic metabolite of benzene, 1,4-benzoquinone (1,4-BQ), reacts rapidly with macromolecules. The authors previously characterized levels of the albumin (Alb) adduct (1,4-BQ-Alb) of this reactive species in populations of workers exposed to benzene. Since high levels of 1,4-BQ-Alb were also measured in unexposed workers from those investigations, the current study was initiated to determine potential sources of 1,4-BQ in the general population. A single blood sample was collected from 191 healthy subjects from the Research Triangle area, NC, USA, to determine the baseline 1,4-BQ-Alb levels and contributing sources. The median 1,4-BQ-Alb at baseline was 550?pmol?g(-1) Alb (interquartile range 435-814?pmol?g(-1)). A second blood sample was collected approximately 3 months later from a subgroup of 33 subjects to estimate the within- and between-person variation in 1,4-BQ-Alb. Standardized questionnaires were administered to collect information about demographic, dietary and lifestyle factors. Multiple linear regression models identified several significant contributors to 1,4-BQ-Alb levels, including gender, body mass index (BMI), the gender-BMI interaction, automobile refuelling, smoking status, and consumption of fruit and the artificial sweetener, aspartame. The authors predicted that these background levels of 1,4-BQ-Alb were equivalent to occupational exposures between 1 and 3 parts per million of benzene. Mixed effects linear models indicated that the random variation in adduct levels was about equally divided between and within subjects. The observations indicate that levels of 1,4-BQ-Alb cover a wide range in the general population, and they support the hypotheses that demographic, diet and lifestyle factors are contributing sources.

Adult↗
PubMedDate not supplied

Sentinel node detection with radiocolloid lymphatic mapping in early invasive cervical cancer.

We assessed the feasibility of sentinel lymph node detection using technicium-99 radiocolloid lymphatic mapping for predicting lymph node metastases in early invasive cervical cancer. Thirty patients with cervical cancer (stages IA2-IIA) underwent preoperative lymphoscintigraphy using technicium-99 intracervical injection and intraoperative lymphatic mapping with a handheld gamma probe. After dissection of the sentinel nodes, the standard procedure of pelvic lymph node dissection and radical hysterectomy was performed as usual. The sentinel node detection rate was 100% (30/30). There were seven (23.3%) cases of microscopic lymph node metastases on pathologic analysis. All of them had sentinel node involvement. Therefore, the sensitivity of sentinel node identification for prediction of lymph node metastases was 100%, and no false negative was found. Preoperative lymphoscintigraphy, coupled with intraoperative lymphatic mapping, located the sentinel nodes accurately in our study patients. This sentinel node detection method appears to be feasible for predicting lymph node metastases.

Aged↗