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E B Ziff

Publications and source records attributed to E B Ziff.

At least 55 records · Page 3Linked to original sources
PubMed1994

Fos family members successively occupy the tyrosine hydroxylase gene AP-1 site after nerve growth factor or epidermal growth factor stimulation and can repress transcription.

Nerve growth factor induces the neuronal-like differentiation of PC12 cells, and epidermal growth factor promotes PC12 viability and is weakly mitogenic. Despite these differences, both growth factors induce indistinguishable patterns of transient delayed transcription of the tyrosine hydroxylase (TH) gene and the expression of proteins encoded by Fos gene family members. Thus, TH expression is sensitive to signaling pathways common to these two growth factors. We show that c-fos and fosB successively occupy an AP-1 site-like element of the TH promoter after nerve growth factor treatment. Furthermore, under conditions of transient transfection, Fos family proteins may synergize with c-jun to transrepress TH gene transcription through the TH-fat-specific element. We show that the target of repression is the AP-1 site-like element that lies within the TH-fat-specific element. We demonstrate that this site is also a major positive acting site for TH control. These results suggest a model in which the long term effect of c-fos family protein expression is to limit the expression of the TH gene. We consider the novel properties of this element in providing temporal and cell type-specific regulation of TH transcription.

Animals↗
PubMed1993

Recognition by Max of its cognate DNA through a dimeric b/HLH/Z domain.

The three-dimensional structure of the basic/helix-loop-helix/leucine zipper domain of the transcription factor Max complexed with DNA has been determined by X-ray crystallography at 2.9 A resolution. Max binds as a dimer to its recognition sequence CACGTG by direct contacts between the alpha-helical basic region and the major groove. This symmetric homodimer, a new protein fold, is a parallel, left-handed, four-helix bundle, with each monomer containing two alpha-helical segments separated by a loop. The two alpha-helical segments are composed of the basic region plus helix 1 and helix 2 plus the leucine repeat, respectively. As in GCN4, the leucine repeat forms a parallel coiled coil.

Amino Acid Sequence↗
PubMed1993

Adenovirus 5 E1A proteins disrupt the neuronal phenotype and growth factor responsiveness of PC12 cells by a conserved region 1-dependent mechanism.

Expression in PC12 cells of adenovirus 5 E1a proteins dramatically changes cell morphology and disrupts neuronal differentiation. We demonstrate that the nerve growth factor (NGF) receptors, p140trk and p75NGFR, as well as the epidermal growth factor receptor are undetectable in E1a-expressing PC12 cells. This correlates with a repression of mRNAs for the chromaffin- and neuronal-specific proteins, tyrosine hydroxylase and peripherin, while more ubiquitously expressed genes remain unaffected. One possible mechanism of E1a action could thus be the repression of a coordinately regulated group of chromaffin- and/or neuronal-specific genes. Furthermore, we show taht E1a conserved region 1, which binds p105Rb and p300, is necessary for this E1a-dependent effect. This indicates that cellular proteins interacting with E1a conserved region 1 may be implicated in growth arrest, expression of neuron-specific functions and orderly differentiation of PC12 cells in response to NGF.

Adenovirus E1A Proteins↗
PubMed1992

A new bind for Myc.

Recent studies centered on the c-Myc basic/helix-loop-helix/leucine zipper (B/HLH/LZ) motifs have led to the identification of a DNA recognition sequence for c-Myc and the isolation of a novel protein that forms a DNA-binding complex with c-Myc in vitro. These advances may make it possible to address directly the long-standing question of c-Myc function in vivo.

Amino Acid Sequence↗
PubMed1992

Biphasic effect of Max on Myc cotransformation activity and dependence on amino- and carboxy-terminal Max functions.

In Ras cotransformation assays, Max exhibited a biphasic effect on Myc transformation activity. Cotransfection of low levels of Max expression plasmid stimulated Myc transformation activity, but cotransfection of high levels suppressed it. Mutations in the functionally undefined Max amino- and carboxy-terminal regions outside of the B/HLH/LZ motif partly separated these activities, suggesting various modes of Max regulation. We demonstrate that the Max protein is a nuclear protein in vivo and identify a carboxy-terminal region similar to nuclear localization signals whose integrity is necessary for efficient localization. Two mutants that delete amino- or carboxy-terminal consensus signals for casein kinase II (CKII) exhibited altered gel mobility and DNA-binding potential in vitro and showed modified transforming potential in the Ras cotransformation assay, suggesting that CKII or a CKII-related enzyme may regulate Max function in vivo. Our data suggest that both the ratio of Myc/Max hetero-oligomers to Max homo-oligomers and Max-specific regulation can contribute to determining the biological activity of Myc in vivo.

Amino Acid Sequence↗
PubMed1992

Nerve growth factor-induced derepression of peripherin gene expression is associated with alterations in proteins binding to a negative regulatory element.

The peripherin gene, which encodes a neuronal-specific intermediate filament protein, is transcriptionally induced with a late time course when nerve growth factor (NGF) stimulates PC12 cells to differentiate into neurons. We have studied its transcriptional regulation in order to better understand the neuronal-specific end steps of the signal transduction pathway of NGF. By 5' deletion mapping of the peripherin promoter, we have localized two positive regulatory elements necessary for full induction by NGF: a distal positive element and a proximal constitutive element within 111 bp of the transcriptional start site. In addition, there is a negative regulatory element (NRE; -179 to -111), the deletion of which results in elevated basal expression of the gene. Methylation interference footprinting of the NRE defined a unique sequence, GGCAGGGCGCC, as the binding site for proteins present in nuclear extracts from both undifferentiated and differentiated PC12 cells. However, DNA mobility shift assays using an oligonucleotide probe containing the footprinted sequence demonstrate a prominent retarded complex in extracts from undifferentiated PC12 cells which migrates with slower mobility than do the complexes produced by using differentiated PC12 cell extract. Transfection experiments using peripherin-chloramphenicol acetyltransferase constructs in which the footprinted sequence has been mutated confirm that the NRE has a functional, though not exclusive, role in repressing peripherin expression in undifferentiated and nonneuronal cells. We propose a two-step model of activation of peripherin by NGF in which dissociation of a repressor from the protein complex at the NRE, coupled with a positive signal from the distal positive element, results in depression of the gene.

Animals↗
PubMed1991

Association of Myn, the murine homolog of max, with c-Myc stimulates methylation-sensitive DNA binding and ras cotransformation.

Myn, a novel murine approximately 18 kd basic/helix-loop-helix/"leucine zipper" (B/HLH/LZ) protein, forms a specific DNA-binding complex with the c-Myc oncoprotein through the HLH/LZ motif in both proteins. c-Myc/Myn recognizes a c-Myc-binding site (GACCACGTGGTC) with higher affinity than either protein by itself. CpG methylation of the recognition site greatly inhibits DNA binding, suggesting that DNA methylation may regulate the c-Myc/Myn complex in vivo. In 3T3 fibroblasts, Myn mRNA levels are induced several-fold by serum with delayed early kinetics, suggesting regulation by immediate-early gene products. Coexpression of Myn in a myc/ras rat embryo fibroblast focus formation assay specifically augmented c-myc transforming activity. We suggest that interaction of Myn with c-Myc stabilizes sequence-specific DNA binding in vivo.

Amino Acid Sequence↗
PubMed1991

Methylation-sensitive sequence-specific DNA binding by the c-Myc basic region.

The function of the c-Myc oncoprotein and its role in cell growth control is unclear. A basic region of c-Myc is structurally related to the basic motifs of helix-loop-helix (HLH) and leucine zipper proteins, which provide sequence-specific DNA binding function. The c-Myc basic region was tested for its ability to bind DNA by attaching it to the HLH dimerization interface of the E12 enhancer binding factor. Dimers of the chimeric protein, termed E6, specifically bound an E box element (GGCCACGTGACC) recognized by other HLH proteins in a manner dependent on the integrity of the c-Myc basic motif. Methylation of the core CpG in the E box recognition site specifically inhibited binding by E6, but not by two other HLH proteins. Expression of E6 (but not an E6 DNA binding mutant) suppressed the ability of c-myc to cooperate with H-ras in a rat embryo fibroblast transformation assay, suggesting that the DNA recognition specificity of E6 is related to that of c-Myc in vivo.

Amino Acid Sequence↗
PubMed1991

Mbh 1: a novel gelsolin/severin-related protein which binds actin in vitro and exhibits nuclear localization in vivo.

We describe the characterization of a novel cDNA, mbh1 (myc basic motif homolog-1), which was found during a search for candidate factors which might interact with the c-Myc oncoprotein. Embedded within the amino acid sequence encoded by mbh1 is a region distantly related to the basic/helix-loop-helix (B/HLH) DNA-binding motif and a potential nuclear localization signal. Mbh1 encodes a polypeptide structurally similar to the actin-severing proteins gelsolin and severin. Translation of mbh1 RNA in rabbit reticulocyte extracts produces an approximately 45 kd protein capable of binding actin-coupled agarose beads in vitro in a Ca2(+)-dependent manner. Antiserum raised to a trpE/mbh1 bacterial fusion protein recognizes an approximately 45 kb protein in murine 3T3 fibroblasts, suggesting that the cDNA encodes the complete Mbh1 protein. Examination of Mbh1 localization in 3T3 fibroblasts by indirect immunofluorescence reveals a larger cell population showing diffuse staining, and a smaller population exhibiting a distinct nuclear stain. Western analysis corroborates this intracellular localization and indicates that total cellular levels and localization of Mbh1 are not affected by the cell growth state. The data suggest that Mbh1 may play a role in regulating cytoplasmic and/or nuclear architecture through potential interactions with actin.

Actins↗
PubMed1991

Differential spatial and temporal expression of two type III intermediate filament proteins in olfactory receptor neurons.

Olfactory receptor neurons (ORNs) do not express the typical neuronal intermediate filament proteins (IFPs), the neurofilament triplet proteins. Immunocytochemical evidence shows that ORNs coexpress vimentin and peripherin but distribute them differently. Specifically, ORNs contain vimentin in dendrites, cell bodies, and axons, but not in terminals in glomeruli; peripherin is present in axons, but excluded from dendrites, cell bodies, and terminal glomeruli. In adult rats, ORN axon fascicles are variably stained with antisera for peripherin; in juvenile rats, staining of fascicles is uniform. Staining with antibody to vimentin is uniform in both adult and juvenile ORN axon fascicles. The unusual pattern of IFP expression and intracellular sorting may have implications for the unique plastic and regenerative capacities of these neurons.

Age Factors↗
PubMed1990

The expression of the neuronal intermediate filament protein peripherin in the rat embryo.

The expression of the neuronal type III intermediate filament protein peripherin was examined in the rat embryo during and following neuronogenesis in the spinal cord and the peripheral nervous system. In situ hybridization analysis reveals that peripherin mRNA is found in the mid-gestational rat embryo in ventral and lateral motoneurons in the spinal cord, and in neurons of all peripheral ganglia examined, including spinal, sympathetic, and enteric ganglia. Peripherin mRNA is seen only in post-migratory motoneurons or neuronal cells in aggregating ganglia, indicating that precursor cells do not express peripherin. To examine the expression of the protein, an affinity-purified antibody (anti-per) specific for a bacterially produced peripherin fusion protein was generated. Anti-per specifically recognizes a 58 kDa, cytoskeletal-enriched, nerve growth factor (NGF)-inducible protein of the expected tissue distribution. Immunocytodetection with anti-per shows that the initiation of peripherin protein synthesis is coincident with the morphological differentiation of neurons. In development, peripherin is one constituent of a program of gene expression activated at terminal neuronal differentiation.

Animals↗
PubMed1990

Nerve growth factor regulates tyrosine hydroxylase gene transcription through a nucleoprotein complex that contains c-Fos.

We have studied nerve growth factor (NGF) regulation of the expression of the tyrosine hydroxylase (TH) gene in PC12 cells. The TH gene encodes the initial and rate-limiting enzyme of the catecholamine biosynthetic pathway. We show that the TH gene is transiently transcriptionally induced by a mechanism reliant on new protein synthesis during 1-2 hr of NGF stimulation, a time following the induction of the c-fos gene at 15 min post-NGF treatment. A potential regulatory sequence located within the TH gene promoter, the TH-FSE, shares homology to a known regulatory element, the fat-specific element (FSE), which is found upstream from genes activated during adipocyte differentiation and binds the Fos-Jun transcription factor complex. We show that the TH-FSE DNA sequence elevates the basal level of transcription from the rat TH promoter and is required for NGF inducibility. This DNA element binds authentic Fos-Jun products produced abundance during NGF stimulation and by in vitro translation. We demonstrate further that the TH-FSE can bind proteins present in PC12 nuclear extracts in a sequence-specific manner. The DNA/nucleoprotein complex that forms increases in abundance during NGF stimulation and reaches a maximum level at 4 hr of treatment. Antibody inhibition studies utilizing an anti-Fos antibody indicate that Fos and/or Fos-related antigen(s) associate with the TH-FSE and suggest that the Fos protein family contributes to the regulation of TH in vivo. These results support a model in which NGF-induced immediate early genes, including c-Fos, contribute to the regulation of delayed early genes such as TH and thereby control neuronal differentiation.

Animals↗
PubMed1990

Functional analysis of an isolated fos promoter element with AP-1 site homology reveals cell type-specific transcriptional properties.

A DNA element located at positions -295 to -289 of the c-fos promoter (FAP site) is highly homologous to a consensus 12-O-tetradecanoyl phorbol-13-acetate-responsive element (TRE) and to a cyclic AMP (cAMP)-responsive element (CRE). We found that an oligonucleotide containing the FAP element was a transcription regulator which was distinct from both the TRE and CRE. When cloned in multiple copies in front of a reporter gene in HeLa cells, the FAP oligonucleotide was a powerful constitutive activator sequence. Conversely, in the same cells, reporter plasmids containing multiple copies of the TRE of the human metallothionein gene required phorbol esters for their induction. In PC12 cells, the FAP oligonucleotide was cAMP responsive. Its activity was mediated through a cAMP-dependent protein kinase II and did not rely on ongoing protein synthesis for activation. Adenovirus E1a proteins activated viral promoters through ATF (activation transcription factor) consensus binding sequences identical to the CRE. However, E1a repressed the FAP oligonucleotide-associated transcriptional activity in HeLa cells. In PC12 cells, E1a neither transactivated nor transrepressed the basal and cAMP-stimulated FAP activity. In contrast, the CRE of the human c-fos promoter located at -60 was weakly induced by cAMP and E1a in both HeLa and PC12 cells. We suggest that the FAP oligonucleotide acts through a factor(s) distinct from those employed by the TRE and CRE and that the FAP-associated protein factor(s) may differ in HeLa and PC12 cells in expression or posttranslational regulation.

Base Sequence↗
PubMed1990

Isolation and characterization of eight tumor necrosis factor-induced gene sequences from human fibroblasts.

A lambda cDNA library was prepared from polyadenylated RNA isolated from quiescent human diploid FS-4 fibroblasts stimulated with tumor necrosis factor for 3 h. Differential screening was used to isolate cDNA sequences that are stimulated by tumor necrosis factor. Eight distinct tumor necrosis factor-stimulated gene sequences (designated TSG-1, -6, -8, -12, -14, -21, -27, and -37) were partially sequenced and compared with known sequences from GenBank. TSG-1 was identical to the gene for interleukin-8. TSG-8 corresponded to the gene for monocyte chemotactic and activating factor. TSG-21 and -27 were identical to the genes for collagenase and stromelysin, respectively. The other four sequences showed no homologies with known genes. Patterns of induction of mRNAs corresponding to the eight cloned cDNAs by various cytokines, growth factors, and activators of second messenger pathways were analyzed in FS-4 cells.

Base Sequence↗
PubMed1990

Elevated c-myc expression in childhood medulloblastomas.

Medulloblastoma is a rare brain tumor usually occurring in late childhood or early adolescence. Little is known regarding the cell of origin or cellular events leading to its malignant transformation. We have studied the expression of developmentally regulated mRNA in tumor samples by the Northern hybridization assay to determine a relative stage at which a block to further differentiation occurs. In a series of five medulloblastoma tumors analyzed, only one of eight markers for cellular differentiation, the glial fibrillary acidic protein mRNA, was expressed at significant levels. Interestingly, three of six medulloblastoma tumor samples were found to have elevated levels of c-myc mRNA. In one of these tumors, we have found evidence of mutation of the c-myc protooncogene. We discuss possible mechanisms of c-myc activation in medulloblastoma tumors.

Base Sequence↗
PubMed1989

DNA-binding motif.

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Amino Acid Sequence↗