Biomedical subjects

L Bai

Publications and source records attributed to L Bai.

At least 19 recordsLinked to original sources

PubMed2002

Dendritic cells pulsed with viral oncolysates potently stimulate autologous T cells from cancer patients.

We demonstrated before that primary operated breast cancer patients contain in their bone marrow (BM) cancer reactive memory T cells (MTC) which have to be re-activated to become tumor infiltrating effector cells. The aim of this study was to optimize an ex vivo stimulation protocol for MTC based on autologous dendritic cells (DC). As source of tumor antigens we used lysates from unmodified tumor cells or from tumor cells infected with Newcastle Disease Virus (NDV) which contain IFN-alpha inducing viral dsRNA as one danger signal. DC from breast cancer patients were pulsed with lysates from the MCF-7 breast cancer line (Tu-L) or from NDV infected MCF-7 cells (TuN-L, viral oncolysates) and compared for stimulatory capacity in an ELISPOT response of autologous BM derived MTC. To analyze potential further danger signals derived from NDV infection, we employed MALDI mass spectrometry, Western blots, FACS cytometry and ELISA tests. DC pulsed with viral oncolysates showed increased expression of co-stimulatory molecules in comparison to Tu-L pulsed DC and induced significantly higher ELISPOT MTC responses. Supernatants from co-cultures of MTC and TuN-L pulsed DC contained increased titers of IFN-alpha and IL-15. NDV infection of tumor cells resulted in a number of differences in protein expression including a heat-shock protein (HSP27) which became phosphorylated. The results suggest that a DC preparation pulsed with viral oncolysate includes danger signals (e.g. dsRNA, cytokines, HSP molecules) and is superior for MTC stimulation to a DC preparation pulsed with lysate from non-infected tumor cells.

Blotting, Western↗

PubMed2002

Generation of dendritic cells from human bone marrow mononuclear cells: advantages for clinical application in comparison to peripheral blood monocyte derived cells.

Dendritic cells (DCs) currently used for vaccination in clinical studies to induce immunity against malignant cells are normally generated from peripheral blood-derived monocytes. Here we studied conditions for the generation of DCs from unseparated human bone marrow (BM) mononuclear cells and compared them functionally with DCs from blood. The two types of DCs, from bone marrow (BM-DC) and peripheral blood (BL-DC), were generated in parallel from the same normal healthy donors by culturing in serum-free X-VIVO 20 medium containing GM-CSF and IL-4, and then the phenotypes and functions were compared. BM-DC generation occurred in 14 days and involved proliferative expansion from CD34 stem cells and differentiation while BL-DC generation occurred in 7 days from CD14 monocytes and involved only differentiation. A 7- to 25-fold higher number of DCs could be obtained from BM than from blood. BM-DC had similar phenotypes as BL-DC. The capacity to stimulate MLR reactivity in allogeneic T lymphocytes was higher with BM-DC than that with BL-DC. Also, the capacity to stimulate autologous memory T cell responses to tetanus toxoid (TT) or tuberculin (PPD) was higher with BM-DC than with BL-DC. These results suggest that BM-DC as produced here may be a very economic and useful source of professional antigen-presenting cells for anti-tumor immunotherapeutic protocols.

Antigen Presentation↗

PubMed2001

Molecular cloning of a murine type III sodium-dependent phosphate cotransporter (Pit-2) gene promoter.

We report the novel cloning and preliminary characterization of a murine type III sodium-dependent phosphate cotransporter (Pit-2) gene promoter. Five promoter/luciferase reporter gene constructs, -1816/+61, -1620/+61, -1223/+61, -600/+61 and -225/+61, showed significant luciferase activity (6-14-fold over background) when transfected into human colon carcinoma (Caco-2) and opossum kidney (OKP) cells.

Animals↗

PubMed2001

ZBP-89, Sp1, and nuclear factor-kappa B regulate epithelial neutrophil-activating peptide-78 gene expression in Caco-2 human colonic epithelial cells.

We reported previously that human colonic epithelial cells produce the C-X-C chemokine epithelial neutrophil-activating peptide-78 (ENA-78) and that its expression is up-regulated in ulcerative colitis. The aim of this study was to investigate the transcriptional regulation of ENA-78 gene expression in Caco-2 intestinal epithelial cells. Reporter gene transfection and electrophoretic mobility shift assay studies demonstrated that cooperation between two regions of the ENA-78 promoter were required for maximal gene expression in interleukin-1beta-stimulated Caco-2 cells. Binding of activated p50/p65 nuclear factor-kappaB to nucleotides -82 to -91 was essential for interleukin-1beta-dependent gene transcription, whereas binding of constitutively expressed zinc-requiring nuclear factors to nucleotides -125 to -134 (site A) was required for basal gene expression. Scanning mutagenesis of site A demonstrated overlapping binding elements at this locus. One site (CTCCCCC) bound Sp1 and Sp3, and overexpression of Sp1 (but not Sp3) up-regulated basal ENA-78 transcription. Another site (CCCCTCCCCC) was found to bind the zinc finger nuclear factor ZBP-89, and overexpression of this protein significantly repressed ENA-78 reporter gene activity. This study demonstrates that ENA-78 gene expression in Caco-2 intestinal epithelial cells is subject to complex regulation involving the coordinate binding of ZBP-89, Sp1, and nuclear factor-kappaB to the ENA-78 promoter.

Animals↗

PubMed2001

Molecular and functional analysis of a novel neuronal vesicular glutamate transporter.

Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Packaging and storage of glutamate into glutamatergic neuronal vesicles requires ATP-dependent vesicular glutamate uptake systems, which utilize the electrochemical proton gradient as a driving force. VGLUT1, the first identified vesicular glutamate transporter, is only expressed in a subset of glutamatergic neurons. We report here the molecular cloning and functional characterization of a novel glutamate transporter, VGLUT2, from mouse brain. VGLUT2 has all major functional characteristics of a synaptic vesicle glutamate transporter, including ATP dependence, chloride stimulation, substrate specificity, and substrate affinity. It has 75 and 79% amino acid identity with human and rat VGLUT1, respectively. However, expression patterns of VGLUT2 in brain are different from that of VGLUT1. In addition, VGLUT2 activity is dependent on both membrane potential and pH gradient of the electrochemical proton gradient, whereas VGLUT1 is primarily dependent on only membrane potential. The presence of VGLUT2 in brain regions lacking VGLUT1 suggests that the two isoforms together play an important role in vesicular glutamate transport in glutamatergic neurons.

Amino Acid Sequence↗

PubMed2001

Enrichment of memory T cells and other profound immunological changes in the bone marrow from untreated breast cancer patients.

Previous studies with animal tumors showed that bone marrow (BM) is a privileged site where potentially lethal tumor cells are controlled in a dormant state by the immune system. Here, we investigated BM of breast cancer patients with respect to tumor cell content, immune activation status and memory T-cell content. BM-derived cells from primary operated breast cancer patients (n = 90) were compared with those from healthy donors (n = 10) and also with cells from respective blood samples. Cytokeratin 19-positive tumor cells were detected by nested polymerase chain reaction. Three-color flow cytometry was used to identify numbers and activation state of T cells, natural killer (NK) cells, monocytes/macrophages and subsets by a panel of monoclonal antibodies (mAbs). The proportion of memory T cells among the CD4 and CD8 T cells was much higher in BM of cancer patients than in healthy donors (p < 0.001). The extent of memory T-cell increase was related to the size of the primary tumor. Patient-derived BM memory CD8 T cells could be shown to contain specific HLA-A2/Her-2/neu(369-377) tetramer binding cells. Patients with disseminated tumor cells in their BM had more memory CD4 T cells and more CD56(+) CD8(+) cells than patients with tumor cell-negative BM. Only some of the immunological changes seen in BM samples of cancer patients were also detectable in peripheral blood samples. Our hypothesis that BM is a special compartment for immunological memory and tumor dormancy is supported by the above findings. The overall results reveal that BM is a valuable additional compartment for immune diagnosis in pathological conditions and possibly for follow-up treatment strategies.

Adult↗

PubMed2001

Retinoic acid (RA) receptor transcriptional activation correlates with inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase (ODC) activity by retinoids: a potential role for trans-RA-induced ZBP-89 in ODC inhibition.

Evaluation of retinoic acid receptor (RAR) subtype-selective alpha and gamma agonists and antagonists and a retinoid X receptor (RXR) class-selective agonist for efficacy at inhibiting both induction of ornithine decarboxylase (ODC) by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse epidermis and rat tracheal epithelial cells and the appearance of papillomas in mouse epidermis treated in the 2-stage tumor initiation-promotion model indicated that (i) RXR class-selective transcriptional agonists, such as MM11246, were not involved in ODC inhibition; (ii) RAR-selective agonists that induce gene transcription from RA-responsive elements (RAREs) were active at low concentrations; (iii) RAR-selective antagonists that bind RARs and inhibit AP-1 activation on the collagenase promoter but do not activate RAREs to induce gene transcription were less effective inhibitors; and (iv) RARgamma-selective retinoid agonists were more effective inhibitors of TPA-induced ODC activity than RARalpha-selective agonists. These results suggest that RARE activation has a more important role in inhibition of ODC activity than RXR activation or AP-1 inhibition and that RARgamma-selective agonists would be the most useful inhibitors of epithelial cell proliferation induced by tumor promoters. The natural retinoid all-trans-RA induced expression of transcription factor ZBP-89, which represses activation of the GC box in the ODC promoter by the transcription factor Sp1.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2001

Susceptibility of insulin-secreting hepatocytes to the toxicity of pro-inflammatory cytokines.

The liver has been suggested as a suitable target organ for reversing type I diabetes by gene therapy. Whilst gene delivery systems to the hepatocyte have yet to be optimized in vivo, whether insulin-secreting hepatocytes are resistant to the autoimmune process that kills pancreatic beta-cells has never been addressed. One of the mechanisms by which beta-cells are killed in type I diabetes is by the release of the cytokines interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) by immune cells. To test the effect of the cytokines on insulin-secreting hepatocytes in vitro we exposed the betacyte, also called the HEP G2ins/g cell which possesses cytokine receptors and can synthesize, store and secrete insulin in a regulated fashion to a glucose stimulus, to the above mentioned cytokines for 14 days. Viability of the HEP G2ins/g cells was similar to that of other liver cell lines/primary cells which were more resistant to the cytokines than the beta-cell line NIT-1. The cytokines had no adverse effect for the first six days on insulin secretion, content and mRNA levels of the HEP G2ins/g cells and insulin secretion in response to 1-h exposure to 20 mM glucose was enhanced 14-fold. Our results indicate that genetically engineered hepatocytes and primary liver cells are more resistant than pancreatic beta-cells to the adverse effects of cytokines offering hope that insulin secreting hepatocytes in vivo made by gene therapy are less likely to be destroyed by cytokines released during autoimmune destruction.

Animals↗

PubMed2001

Increased vascular endothelial growth factor expression in human hearts with microvascular fibrin.

We have shown that microvascular changes that promote fibrin deposition in human cardiac allografts adversely affect clinical outcome. However, some allografts exhibit phenotypic changes in capillaries following the deposition of fibrin, which subsequently provide a significant survival advantage. The mechanism(s) involved in these capillary changes is(are) unknown. Similarly, although we have shown a significant temporal relationship between microvascular fibrin deposition and vascular endothelial growth factor (VEGF) immunoreactivity in cardiac allografts, the cellular source and relative changes in VEGF gene expression under these conditions are not known. Using immunocytochemical techniques, biopsies devoid of fibrin deposition lacked detectable VEGF immunoreactivity, whereas biopsies with fibrin deposition showed VEGF immunoreactivity in cardiocytes, interstitium, and some microvessels. By in situ hybridization, biopsies without microvascular fibrin deposition showed faint VEGF hybridization signals confined primarily to cardiocytes. In biopsies with fibrin deposition, strong VEGF hybridization signals were detected in cardiocytes, arteriolar smooth muscle cells were occasionally labeled, and endothelial cells were rarely labeled. By quantitative RT-PCR, biopsies with fibrin deposition (n=5) relatively expressed approximately three-fold more VEGF mRNA than biopsies without fibrin deposition (n=5 P=0.02). Serum VEGF titers also were greater (P=0.01) in recipients with fibrin deposition (372.9+/-66.7 pg/ml n=18) compared to recipients without fibrin deposition (172.1+/-25.0 pg/ml n=16). Collectively, these results support the hypothesis that increased myocyte-derived VEGF production following microvascular fibrin deposition in transplanted human hearts may act in a paracrine manner to promote activational and phenotypic changes in capillaries that provide a survival advantage for the allografts.

Biopsy↗

PubMed2001

Therapy of human tumors in NOD/SCID mice with patient-derived reactivated memory T cells from bone marrow.

In an analysis of 84 primary-operated breast cancer patients and 11 healthy donors, we found that the bone marrow of most patients contained memory T cells with specificity for tumor-associated antigens. Patients' bone marrow and peripheral blood contained CD8+ T cells that specifically bound HLA/peptide tetramers. In short-term culture with autologous dendritic cells pre-pulsed with tumor lysates, patients' memory T cells from bone marrow (but not peripheral blood) could be specifically reactivated to interferon-gamma-producing and cytotoxic effector cells. A single transfer of restimulated bone-marrow T cells into NOD/SCID mice caused regression of autologous tumor xenotransplants associated with infiltration by human T cells and tumor-cell apoptosis and necrosis. T cells from peripheral blood showed much lower anti-tumor reactivity. Our findings reveal an innate, specific recognition of breast cancer antigens and point to a possible novel cancer therapy using patients' bone-marrow-derived memory T cells.

Amino Acid Sequence↗

PubMed2001

ZBP-89 promotes growth arrest through stabilization of p53.

Transcription factor p53 can induce growth arrest and/or apoptosis in cells through activation or repression of downstream target genes. Recently, we reported that ZBP-89 cooperates with histone acetyltransferase coactivator p300 in the regulation of p21(waf1), a cyclin-dependent kinase inhibitor whose associated gene is a target gene of p53. Therefore, we examined whether ZBP-89 might also inhibit cell growth by activating p53. In the present study, we demonstrate that elevated levels of ZBP-89 induce growth arrest and apoptosis in human gastrointestinal cell lines. The ZBP-89 protein accumulated within 4 h, and the p53 protein accumulated within 16 h, of serum starvation without changes in p14ARF levels, demonstrating a physiological increase in the cellular levels of these two proteins. Overexpression of ZBP-89 stabilized the p53 protein and enhanced its transcriptional activity through direct protein-protein interactions. The DNA binding and C-terminal domains of p53 and the zinc finger domain of ZBP-89 mediated the interaction. A point mutation in the p53 DNA binding domain, R273H, greatly reduced ZBP-89-mediated stabilization but not their physical interaction. Furthermore, ZBP-89 formed a complex with p53 and MDM2 and therefore did not prevent the MDM2-p53 interaction. However, heterokaryon assays demonstrated that ZBP-89 retained p53 in the nucleus. Collectively, these data indicate that ZBP-89 regulates cell proliferation in part through its ability to directly bind the p53 protein and retard its nuclear export. Our findings further our understanding of how ZBP-89 modulates cell proliferation and reveals a novel mechanism by which the p53 protein is stabilized.

Animals↗

PubMed2001

Regulation of the human sodium-phosphate cotransporter NaP(i)-IIb gene promoter by epidermal growth factor.

The intestinal sodium-phosphate cotransporter (NaP(i)-IIb) plays a major role in intestinal P(i) absorption. Epidermal growth factor (EGF) is involved in the regulation of P(i) homeostasis. However, the role of EGF in intestinal NaP(i)-IIb regulation is not clear. The current studies showed that EGF decreased NaP(i)-IIb mRNA abundance by 40-50% in both rat intestine and Caco-2 cells. To understand the mechanism of this regulation, we cloned the human NaP(i)-IIb gene and promoter region and studied the effect of EGF on NaP(i)-IIb gene transcription. The human NaP(i)-IIb gene has 12 exons and 11 introns. Two transcription initiation sites were identified by primer extension. Additionally, 2.8 kb of the 5'-flanking region of the gene was characterized as a functional promoter in human intestinal (Caco-2) and human lung (A549) cells. Additional studies showed that EGF inhibited promoter activity by 40-50% in Caco-2 cells and that actinomycin D treatment abolished this inhibition. EGF had no effect on promoter activity in lung (A549) cells. We conclude that the human NaP(i)-IIb gene promoter is functional in Caco-2 and A549 cells and that the gene is responsive to EGF by a transcriptionally mediated mechanism in intestinal cells.

Animals↗

PubMed2001

Transcriptional regulation of rat Na(+)/H(+) exchanger isoform-2 (NHE-2) gene by Sp1 transcription factor.

The rat Na(+)/H(+) exchanger isoform-2 (NHE-2) gene promoter lacks a TATA box and is very GC rich. A minimal promoter extending from bp -36 to +116 directs high-level expression of NHE-2 in mouse inner medullary collecting duct (mIMCD-3) cells. Four Sp1 consensus elements were found in this region. The introduction of mutations within these Sp1 consensus elements and DNA footprinting revealed that only two of them were utilized and are critical for basal transcriptional activation in mIMCD-3 cells. The use of Sp1, Sp3, and Sp4 antisera in electrophoretic mobility shift assays demonstrated that Sp1, Sp3, and Sp4 bound to this minimal promoter. We further analyzed the transcriptional regulation of NHE-2 by members of the Sp1 multigene family. In Drosophila SL2 cells, which lack endogenous Sp1, the minimal promoter cannot drive transcription. Introduction of Sp1 activated transcription over 100-fold, suggesting that Sp1 is critical for transcriptional regulation. However, neither Sp3 nor Sp4 was able to activate transcription in these cells. Furthermore, in mIMCD-3 cells, Sp1-mediated transcriptional activation was repressed by expression of Sp3 and Sp4. These data suggest that Sp1 is critical for the basal promoter function of rat NHE-2 and that Sp3 and Sp4 may repress transcriptional activation by competing with Sp1 for binding to core cis-elements.

Animals↗

PubMed2001

Epidermal growth factor regulation of rat NHE2 gene expression.

Epidermal growth factor (EGF) is involved in acute regulation of Na(+)/H(+) exchangers (NHEs), but the effect of chronic EGF administration on NHE gene expression is unknown. The present studies showed that EGF treatment increased NHE2-mediated intestinal brush-border membrane vesicle Na(+) absorption and NHE2 mRNA abundance by nearly twofold in 19-day-old rats. However, no changes were observed in renal NHE2 mRNA or intestinal and renal NHE3 mRNA abundance. To understand the mechanism of this regulation, we developed the rat intestinal epithelial (RIE) cell as an in vitro model to study the effect of EGF on NHE2 gene expression. EGF increased functional NHE2 activity and mRNA abundance in cultured RIE cells, and this stimulation could be blocked by actinomycin D (a transcriptional inhibitor). Additionally, NHE2 promoter reporter gene assays in transiently transfected RIE cells showed an almost twofold increase in promoter activity after EGF treatment. We conclude that rat NHE2 activity can be stimulated by chronic EGF treatment and that this response is at least partially mediated by gene transcription.

Animals↗

PubMed2001

Spatiotemporal properties of an evoked population activity in rat sensory cortical slices.

We have examined the spatiotemporal properties of ensemble activity, an evoked all-or-none polysynaptic activity in rat neocortical slices. Ensemble activity occurred in cortical slices bathed in normal artificial cerebrospinal fluid (ACSF) and was evoked by a single electrical shock either to the white matter or directly to the cortical tissue. This activity was seen in slices of somatosensory and auditory cortices; in other cortical areas we have not been able to evoke it. The activity developed 10 to 250 ms poststimulus and lasted 280 +/- 120 ms in local field potential (LFP) recordings. Voltage-sensitive dye imaging showed that this activity was an area of activation 0.8 +/- 0.4 mm wide that propagated slowly (11.4 +/- 6.2 mm/s, n = 60, 6 animals) in the horizontal direction. Due to this propagation, the actual duration in the whole tissue may be longer (approximately 400 ms) than that recorded by a single LFP electrode. Ensemble activity produced a low-amplitude optical signal (7-14% of the interictal-like spikes in the same tissue), suggesting a moderate net depolarization of the population. These were very different from hyperexcitable (epileptiform) events in the same tissue that had about 10 times the optical signal amplitude and propagated at 125 +/- 24 mm/s (n = 21, 6 animals). On a global spatial scale (approximately 0.8 mm wide in layers II-III) ensemble activity had a smooth waveform in voltage-sensitive dye signals (population transmembrane potential). On a local scale, field potential recordings showed large fluctuations with complex oscillations and substantial trial-to-trial variation. This suggests that oscillations in cortical circuits occurred only in small clusters of correlated neurons. Ensemble activity was sensitive to the excitation-inhibition balance of the local network. Antagonists of N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and GABAa receptors, and muscarinic agonists and other modest manipulations such as increasing bath concentration of Mg(2+) to 2.5-4 mM (normally at 2 mM), or K(+) to 5-7 mM (normally 3 mM), all significantly reduced the probability of evoking the activity. The metabotropic glutamate receptor agonist, aminocyclopentane-1,3-dicarboxylic acid, blocked the activity at a low concentration (10-15 microM), while the antagonist (R,S)-alpha-methyl-4-carboxyphenylglycine had no effect even at high concentration (240 microM). Our data suggest that locally organized neuronal clusters may play a role in the organization of oscillatory activities in the gamma band and may participate in cortical integration/amplification occurring on a scale of approximately 1 mm x 300 ms.

Animals↗

PubMed2000

Nuclear factor 1 (NF1) affects accurate termination and multiple-round transcription by human RNA polymerase III.

We have shown previously that the TFIIIC1/TFIIIC1' fraction interacts specifically with the VA1 terminator regions to affect both termination and initiation/reinitiation of transcription by human RNA polymerase III. Here, we further purified the VA1 terminator-binding factor to apparent homogeneity and found, by peptide sequence analysis, that it belongs to the NF1 protein family. NF1 interacts specifically with the NF1-binding sites within the terminator regions of the VA1 gene and with two subunits (TFIIIC220 and TFIIIC110) of human TFIIIC2. Immunodepletion with anti-NF1 antibodies dramatically decreases transcription from the VA1 template in nuclear extract, and mutation at the NF1-binding site in the terminator region of the VA1 gene selectively affects multiple-round transcription (reinitiation of transcription) and termination. In addition, NF1 acts in conjunction with TFIIIC to promote accurate termination by RNA polymerase III on a C-tailed VA1 template.

Base Sequence↗

PubMed2000

Molecular cloning of murine sodium-phosphate cotransporter type IIb (Na/P(i)-IIb) gene promoter and characterization of gene structure.

We report the cloning of the murine Na/P(i)-IIb cotransporter gene, which spans more than 18 kilobases and consists of 12 introns and 13 exons. Three promoter/reporter gene constructs, -159/+73, -429/+73 and -954/+73, showed significant luciferase activity (22-82-fold over background) when transfected into in rat intestinal epithelial (RIE-1) cells.

Animals↗

PubMed2000

Transcription factor ZBP-89 cooperates with histone acetyltransferase p300 during butyrate activation of p21waf1 transcription in human cells.

Inducible p53-independent regulation of the cyclin-dependent kinase inhibitor p21(waf1) transcription is mediated through proximal GC-rich sites. Prior studies have shown that Sp1, Sp3, and the histone acetylase co-activator p300 are components of the complexes binding to these sites. Although Sp1 and Sp3 collaborate with p300, a direct interaction between Sp1 and p300 does not occur. This study sought to determine whether ZBP-89 rather than Sp1 is the direct target of p300 during butyrate induction of p21(waf1). ZBP-89 (BFCOL1, BERF-1, ZNF 148) is a Krüppel-type zinc finger transcription factor that binds to GC-rich elements and represses or activates known target genes. Adenoviral-mediated expression of ZBP-89 in HT-29 cells revealed that ZBP-89 potentiates butyrate induction of endogenous p21(waf1) gene expression. Further, cotransfection of a ZBP-89 expression vector with a 2.3-kilobase p21(waf1) reporter recapitulated the potentiation by butyrate. DNase I footprinting analysis of the human p21(waf1) promoter with recombinant ZBP-89 identified a binding site at -245 to -215. Electrophoretic mobility shift assays confirmed that both recombinant and endogenous ZBP-89 and Sp1 bind to this element. The potentiation was abolished in the presence of adenoviral protein E1A. Deletion of the N-terminal domain of ZBP-89 abolished the potentiation mediated by butyrate treatment. This same deletion mutant abolished the ZBP-89 interaction with p300. Cotransfection of p300 with ZBP-89 stimulated the p21(waf1) promoter in the absence of butyrate. p300 co-precipitated with ZBP-89 but not with Sp1, whereas ZBP-89 co-precipitated with Sp1. Together, these findings demonstrate that ZBP-89 also plays a critical role in butyrate activation of the p21(waf1) promoter and reveals preferential cooperation of this four-zinc finger transcription factor with p300.

Acetyltransferases↗