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A binding site for the transcription factor Grainyhead/Nuclear transcription factor-1 contributes to regulation of the Drosophila proliferating cell nuclear antigen gene promoter.

The Drosophila proliferating cell nuclear antigen promoter contains multiple transcriptional regulatory elements, including upstream regulatory element (URE), DNA replication-related element, E2F recognition sites, and three common regulatory factor for DNA replication and DNA replication-related element-binding factor genes recognition sites. In nuclear extracts of Drosophila embryos, we detected a protein factor, the URE-binding factor (UREF), that recognizes the nucleotide sequence 5'-AAACCAGTTGGCA located within URE. Analyses in Drosophila Kc cells and transgenic flies revealed that the UREF-binding site plays an important role in promoter activity both in cultured cells and in living flies. A yeast one-hybrid screen using URE as a bait allowed isolation of a cDNA encoding a transcription factor, Grainyhead/nuclear transcription factor-1 (GRH/NTF-1). The nucleotide sequence required for binding to GRH was indistinguishable from that for UREF detected in embryo nuclear extracts. Furthermore, a specific antibody to GRH reacted with UREF in embryo nuclear extracts. From these results we conclude that GRH is identical to UREF. Although GRH has been thought to be involved in regulation of differentiation-related genes, this study demonstrates, for the first time, involvement of a GRH-binding site in regulation of the DNA replication-related proliferating cell nuclear antigen gene.

Animals↗

Retroviral-mediated gene transfer and expression of human phenylalanine hydroxylase in primary mouse hepatocytes.

Genetic therapy for phenylketonuria (severe phenylalanine hydroxylase deficiency) may require introduction of a normal phenylalanine hydroxylase gene into hepatic cells of patients. We report development of a recombinant retrovirus based on the N2 vector for gene transfer and expression of human phenylalanine hydroxylase cDNA in primary mouse hepatocytes. This construct contains an internal promoter of the human alpha 1-antitrypsin gene driving transcription of the phenylalanine hydroxylase cDNA. Primary mouse hepatocytes were isolated from newborn mice, infected with the recombinant virus, and selected for expression of the neomycin-resistance gene. Hepatocytes transformed with the recombinant virus contained high levels of human phenylalanine hydroxylase mRNA transcripts originating form the retroviral and internal promoters. These results demonstrate that the transcriptional regulatory elements of the alpha 1-antitrypsin gene retain their tissue-specific function in the recombinant provirus and establish a method for efficient transfer and high-level expression of human phenylalanine hydroxylase in primary hepatocytes.

Animals↗

Cloning of the chicken immunoglobulin joining (J)-chain gene and characterization of its promoter region.

Three overlapping genomic clones of the chicken immunoglobulin joining (J) chain were isolated and then characterized using restriction enzyme analysis, Southern blot analysis with cDNA probes, and DNA sequencing. The gene consisted of four exons separated by a 2.6-kb intron 1, a 0.9-kb intron 2, and a 0.5-kb intron 3. A transcriptional initiation site was identified by a primer extension method using mRNA and cDNA, indicating that exon 1 was 86 bp encoding 20 amino acid residues. A TATA box was positioned at 29 approximately 25 bp upstream of exon 1. Exons, 2, and 3 consisted of 133 bp and 81 bp, encoding 43 and 26 amino acid residues of the mature protein, respectively. Exon 4 consisted of 202 bp encoding 66 amino acid residues and 1.2 kb of untranslated sequence. Deletion mutants of a 4.1-kb genomic fragment containing exon 1 showed high levels of promoter activities when examined in luciferase reporter assays following transfection into the DT-40 chicken B-cell line. These results suggest that the chicken J-chain gene consists of four exons and three introns and that the transcriptional regulatory elements may be present within 3.8 kb upstream of exon 1.

Amino Acid Sequence↗

Dissociation of transforming and trans-activation functions for bovine papillomavirus type 1.

It has been shown that genetic information encoded by the 3' open reading frames (ORFs), E2, E3, E4 and E5, of bovine papillomavirus type 1 (BPV-1), is sufficient to induce cellular transformation of certain mouse cells. The product of the E2 ORF has further been shown to be responsible for the trans-activation of a transcriptional regulatory element located in the noncoding region (NCR) of the BPV-1 genome. To examine whether or not the E2 trans-activation function is encoded by the same gene that encodes the 3' ORF viral transformation function, we have now analysed the expression of the trans-activation function in series of mouse C127 cells transformed by BPV-1 deletion mutants. In addition, using mutated complementary DNA clones generated by the insertion of a premature translational termination linker into different sites of a BPV-1 cDNA clone containing the 3' ORFs intact, we demonstrate that transformation and transcriptional trans-activation functions can be dissociated and that they map respectively to the E5 and E2 ORFs.

Acetyltransferases↗

Pan: a transcriptional regulator that binds chymotrypsin, insulin, and AP-4 enhancer motifs.

Two cDNAs were cloned that encode proteins (Pan-1 and Pan-2, with predicted molecular masses of 67.4 and 67.7 kD, respectively) that bind to a conserved transcriptional regulatory element present in pancreatic exocrine genes. The cDNAs are virtually identical in the region that encodes the amino-terminal 525 amino acids; they differ only by a 3-nucleotide insertion that results in the addition of a single amino acid. The cDNAs, however, code for related, but divergent, carboxy-terminal regions. Expression of the cloned cDNAs in HeLa cells activates expression of a cotransfected chimeric gene containing multimers of the pancreatic conserved element linked to a minimal promoter. Pan-1 and Pan-2 bind to the consensus sequence CAC/GCTGT/C, the CACCTGTC motif, which is present in transcriptional control elements of several genes. Both Pan-1 and Pan-2 bind to related motifs present in the rat insulin enhancer as well as a DNA segment containing the SV40 AP-4 element. The Pan-1 and Pan-2 cDNAs display extensive sequence identity with partial cDNA clones encoding E12 and E47, which bind to the immunoglobulin kappa E2 cis-active element, and may be derived from the same gene. These factors belong to a set of genetically distinct molecules, including AP-4 and MLTF, that bind to the CACCTGTC motif or related sequences. The Pan/E12,E47 proteins also show structural similarity with the Drosophila daughterless protein, MyoD, Myogenin, and Myf-5.

Amino Acid Sequence↗

Transcription analysis of porcine circovirus (PCV).

This study focuses on gene expression of porcine circovirus (PCV) in order to identify viral genes and their corresponding mRNA transcripts. By northern blot analysis, the existence of three mRNAs could be demonstrated. Two mRNAs are encoded by the viral (-)-strand and one is encoded by the viral (+)-strand. The (+)-strand encoded mRNA transcript is 990 nucleotides (nt) long and corresponds to the open reading frame (ORF) 1, as shown by S1 mapping. The start point of this transcript is located at pos. 1238, as determined by primer extension analysis and rapid amplification of cDNA ends (RACE). The transcript is spliced as shown by direct reverse sequencing and RACE. It contains an untranslated "leader"-sequence 119 nt in size (pos. 1238 to 1120) which is joined to exon 2 of the ORF 1 transcript at pos. 737. The transcriptional regulatory elements have been identified functionally by CAT assays. They are located within a 258 base points (bp) fragment (pos. 1168 to 1425).

Animals↗

The nucleotide sequence of abutilon mosaic virus reveals prokaryotic as well as eukaryotic features.

The complete nucleotide sequence of abutilon mosaic virus (West Indian isolate, AbMVa) is presented. The resulting genomic structure resembles that of other geminiviruses which are transmitted by the whitefly Bemisia tabaci: AbMV possesses a bipartite circular genome with bidirectional orientation of the open reading frames (ORF). Both components have a common region of 180 bases with 99% homology while the rest of their sequence is distinct. Eukaryotic regulatory transcription elements precede most ORFs and polyadenylation signals are present at the end of most ORFs. However, two ORFs show features of prokaryotic genes. This chimaeric genome organisation is discussed with reference to the finding that AbMV DNA is present in plastids as well as in the nucleus of infected cells.

Amino Acid Sequence↗

Myocardin is a critical serum response factor cofactor in the transcriptional program regulating smooth muscle cell differentiation.

The SAP family transcription factor myocardin functionally synergizes with serum response factor (SRF) and plays an important role in cardiac development. To determine the function of myocardin in the smooth muscle cell (SMC) lineage, we mapped the pattern of myocardin gene expression and examined the molecular mechanisms underlying transcriptional activity of myocardin in SMCs and embryonic stem (ES) cells. The human and murine myocardin genes were expressed in vascular and visceral SMCs at levels equivalent to or exceeding those observed in the heart. During embryonic development, the myocardin gene was expressed abundantly in a precise, developmentally regulated pattern in SMCs. Forced expression of myocardin transactivated multiple SMC-specific transcriptional regulatory elements in non-SMCs. By contrast, myocardin-induced transactivation was not observed in SRF(-/-) ES cells but could be rescued by forced expression of SRF or the SRF DNA-binding domain. Furthermore, expression of a dominant-negative myocardin mutant protein or small-interfering-RNA-induced myocardin knockdown significantly reduced SM22 alpha promoter activity in SMCs. Most importantly, forced expression of myocardin activated expression of the SM22 alpha, smooth muscle alpha-actin, and calponin-h1 genes in undifferentiated mouse ES cells. Taken together, these data demonstrate that myocardin plays an important role in the SRF-dependent transcriptional program that regulates SMC development and differentiation.

Amino Acid Sequence↗

The transcriptional promoter regulates hypermutation of the antibody heavy chain locus.

A somatic process introduces mutations into antibody variable (V) region genes at a high rate in many vertebrates, and is a major source of antibody diversity. The mechanism of this hypermutation process remains enigmatic, although retrospective studies and transgenic experiments have recently suggested a role for transcriptional regulatory elements. Here, we demonstrate that mouse heavy (H) chain loci in which the natural VH promoter has been replaced by a heterologous promoter undergo hypermutation. However, while the distribution of mutation in such loci appears normal, the frequency of mutation does not. Conversely, moving the VH promoter 750 bp upstream of its normal location results in a commensurate change in the site specificity of hypermutation in H chain loci, and the foreign DNA inserted into the VH leader intron to produce this promoter displacement is hypermutated in a manner indistinguishable from natural Ig DNA. These data establish a direct mechanistic link between the IgH transcription and hypermutation processes.

Animals↗

Molecular cloning and sequence analysis of the Anticarsia gemmatalis multicapsid nuclear polyhedrosis virus GP64 glycoprotein.

The gp64 locus of Anticarsia gemmatalis multicapsid nucleopolyhedrovirus isolate Santa Fe (AgMNPV-SF) was characterised molecularly in our laboratory. To this end, we have located and cloned a AgMNPV-SF genomic DNA fragment containing the gp64 gene and sequenced the complete gp64 locus. Nucleotide sequence analysis indicated that the AgMNPV gp64 gene consists of a 1500 nucleotide open reading frame (ORF), encoding a protein of 499 amino acids. Of the seven gp64 homologues identified to date, the AgMNPV gp64 ORF shared most sequence similarity with the gp64 gene of Orgyia pseudotsugata MNPV. The GP64 from AgMNPV is the smallest baculoviral envelope glycoprotein found to date, differing in 10 or more residues from the other group I nucleopolyhedroviruses. The biological activity of AgMNPV GP64 protein was assessed by cell fusion assays in UFL-AG-286 cells using the obtained recombinant plasmids. In the upstream and downstream regions, relative to the gp64 ORF, we found different conserved transcriptional and post-transcriptional regulatory elements, respectively.

5' Untranslated Regions↗

Characterization of the 5' flanking region of the human NPT-1 Na+/phosphate cotransporter gene.

To elucidate the expression and regulation of the human type I Na+/phosphate transporter gene (NPT-1), the 5' flanking region of the NPT-1 gene was cloned, and its nucleotide sequence and function were determined. A genomic clone that contained approximately 14.0 kb of the 5'-flanking region of the NPT-1 gene was isolated. A single transcription start site was located 104 base pairs (bp) upstream of the 3' end of exon 1. In addition to the sequence of the 5'-flanking region contained a sequence weakly homologous to a TATA box at position -41 to -36 and many transcriptional regulatory elements. Transient expression revealed that a 45-bp region of proximal to exon 1, which contained TATA-like sequence, was sufficient for promoting luciferase expression in OK-cells derived from opossum kidney proximal tubule.

Carrier Proteins↗

PKB rescues calcineurin/NFAT-induced arrest of Rag expression and pre-T cell differentiation.

Protein kinase B (PKB), an Ag receptor activated serine-threonine kinase, controls various cellular processes including proliferation and survival. However, PKB function in thymocyte development is still unclear. We report PKB as an important negative regulator of the calcineurin (CN)-regulated transcription factor NFAT in early T cell differentiation. Expression of a hyperactive version of CN induces a profound block at the CD25+CD44- double-negative (DN) 3 stage of T cell development. We correlate this arrest with up-regulation of Bcl-2, CD2, CD5, and CD27 proteins and constitutive activation of NFAT but a severe impairment of Rag1, Rag2, and intracellular TCR-beta as well as intracellular TCR-gammadelta protein expression. Intriguingly, simultaneous expression of active myristoylated PKB inhibits nuclear NFAT activity, restores Rag activity, and enables DN3 cells to undergo normal differentiation and expansion. A correlation between the loss of NFAT activity and Rag1 and Rag2 expression is also found in myristoylated PKB-induced CD4+ lymphoma cells. Furthermore, ectopic expression of NFAT inhibits Rag2 promoter activity in EL4 cells, and in vivo binding of NFATc1 to the Rag1 and Rag2 promoter and cis-acting transcription regulatory elements is verified by chromatin immunoprecipitation analysis. The regulation of CN/NFAT signaling by PKB may thus control receptor regulated changes in Rag expression and constitute a signaling pathway important for differentiation processes in the thymus and periphery.

Animals↗

Human thyroxine-binding globulin gene: complete sequence and transcriptional regulation.

T4-binding globulin (TBG) is a glycoprotein of hepatic origin which transports thyroid hormone in serum. To characterize the human TBG (hTBG) gene, we studied its genomic organization, promoter activity, and regulation. To this purpose, we isolated from liver a complete hTBG cDNA clone containing the 5'-untranslated region and localized the transcription start site (TSS). The analysis of genomic clones revealed that the hTBG gene consists of five exons and that its exon-intron organization is similar to that of other members of the serine protease inhibitor family. The first exon (exon 0) is a short noncoding sequence located 1.62 kilobase pairs (kbp) upstream from exon 1. Potential cis-acting transcriptional regulatory elements including a TATA box, a CAAT box, and a hepatocyte nuclear factor-1 binding motif were identified in the upstream region. A reporter gene in which 3.2 kbp of the 5'-flanking region, including exon 0, was inserted upstream of the bacterial chloramphenicol acetyltransferase gene showed significant activity when transfected into a hepatblastoma-derived (HepG2) cell line. The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate, down-regulated the promoter activity by more than 80% and completely inhibited hTBG synthesis, whereas thyroid hormone, glucocorticoid, estrogen, and nicotinic acid had little, if any, effect. A series of 5'-deletions revealed that the fragment -218 to +4 from the TSS had the highest promoter activity, nearly 1000-fold greater than the promoterless chloramphenicol acetyltransferase construct. When nonhepatocyte-derived cell lines (CV-1 and CHO) were tested, promoter activity was reduced by a factor of 100, showing that the promoter works in liver-specific manner. The region -218 to -102 contains liver-specific enhancer elements, since deletion to nucleotide -101 resulted in a profound reduction of the promoter activity in HepG2 cells but not in CV-1 or CHO cells. On the other hand, mutational disruption of the putative hepatocyte nuclear factor-1 site (located 65 bp upstream of the TSS) completely abolished the promoter activity in all cell lines, indicating that this site is absolutely required for the transcription of the hTBG gene.

Amino Acid Sequence↗

Production, characterization and functional activities of v-Ski in cultured cells.

The v-ski oncogene was introduced into mammalian cells in order to study its biochemical and biological properties. v-Ski, produced at relatively high levels by mouse L cells stably transfected with this DNA, was localized to the cell nucleus, was of correct apparent molecular mass, and was capable of complexing with DNA. Transient transfection of reporter plasmids into control or Ski producing mouse L cells revealed that Ski acts as a transcriptional activator of various transcriptional regulatory elements, including CMVie, RSV LTR and SV40. These results indicate that mouse L cells contain the nuclear cofactor(s) required for the ability of v-Ski to bind to DNA and also suggest that the v-Ski present within the cells is functional.

Animals↗

Identification and characterization of a beta-globin promoter-binding factor from murine erythroleukemia cells.

We have identified a DNA-binding activity with specificity for the beta DRE, an evolutionarily conserved transcriptional regulatory element in mammalian adult beta-globin promoters. This binding activity, which we term beta DRf, for beta-globin direct repeat factor, was detected in fractionated nuclear extracts from the murine erythroleukemia cell line and has been partially purified from undifferentiated cells. beta DRf makes symmetric contacts on the two copies of its recognition sequence on both strands and introduces a bend into the DNA helix upon binding. While the factor displays a low binding affinity for the beta DRE in isolation, it binds to the intact beta-globin promoter and DNA fragments containing multiple beta DRE-binding sites with high affinity. A correlation between beta DRf binding affinity and transcriptional activity of beta DRE mutant promoters suggests that this factor stimulates transcription of the beta-globin promoter in vivo.

Animals↗

Regulation of the human IgE receptor (Fc epsilon RII/CD23) by EBV. Localization of an intron EBV-responsive enhancer and characterization of its cognate GC-box binding factors.

EBV infection of human B lymphocytes induces expression of the low affinity IgE receptor, Fc epsilon RII/CD23. CD23 is constitutively expressed in EBV-immortalized B cells and may play an essential role in immortalization. We previously explored the regulation of CD23 by EBV, showing that induction results from transcriptional activation that is mediated, in part, by an EBV-responsive transcriptional regulatory element in the 5' region of CD23 (-229 to +305 relative to the type a promoter). We now report the localization of the regulatory element and characterization of its cognate DNA-binding proteins. Reporter gene assays in EBV-positive and -negative lines localized a functional EBV-responsive enhancer to a 37-bp fragment (+248 to +284) that contains a GC-rich sequence (GC box) within intron I of type a CD23. This fragment was shown by mobility shift assays to specifically bind nuclear protein(s) from EBV-positive lines, but not EBV-negative lines. Mutation of the GC box resulted in a loss of protein-binding activity, implicating involvement of a GC box-binding protein in the DNA/protein interaction. Supershift assays suggested that the ubiquitous GC box-binding transcription factor, Sp1, is not a part of the complex, and UV-crosslinking studies demonstrated that the DNA/protein complex contains at least two proteins that differ in size from other known GC box-binding proteins. Binding of these proteins to the enhancer element requires phosphorylation, because phosphatase treatment of nuclear extracts abolished formation of the DNA/protein complex. These studies reveal the presence of an EBV-responsive enhancer element in intron I of type a CD23 and implicate a GC box-binding transcription factor in the activation of CD23 by EBV.

Base Sequence↗

Brain proteins in plants: an Arabidopsis homolog to neurotransmitter pathway activators is part of a DNA binding complex.

The G box is a well-characterized cis-acting DNA regulatory element found in the promoters of several seemingly unrelated plant genes, including the alcohol dehydrogenase (Adh) gene of Arabidopsis thaliana. Using a monoclonal antibody screening approach coupled with electrophoretic mobility shift assays, we have isolated a cDNA clone encoding a protein that is part of the in vitro protein/G box complex. The derived amino acid sequence is homologous to a class of proteins in mammalian brains described as protein kinase C inhibitors and as activators of tyrosine and tryptophan hydroxylases, the rate-limiting enzymes in the pathways leading to the catecholamines and serotonin. The fact that a homologous member of this regulatory protein family is found in plants and is associated with binding to transcriptional regulatory elements suggests a much wider role for these proteins.

Amino Acid Sequence↗

Characterization of mouse cathepsin K gene, the gene promoter, and the gene expression.

Cathepsin K, a lysosomal cysteine protease, is abundantly and selectively expressed in osteoclasts and has a specialized role in osteoclast-mediated bone resorption. In contrast to function studies, transcription regulation of cathepsin K remains largely unknown. In this study, the gene encoding mouse cathepsin K and the promoter have been isolated and completely sequenced. In addition, the temporal and spatial expressions of cathepsin K have been characterized. Intrachromosomal mapping studies revealed that the gene contains eight exons and seven introns spanning approximately 10.6 kb of genomic DNA, a genomic organization that was highly conserved with respect to its human homology. Analysis of the 9 kb 5' flanking region indicates that this gene lacks canonical TATA and CAAT boxes and contains multiple putative transcription regulatory elements which are also present in the comparable position of 5' flanking region of human cathepsin K gene. Mouse cathepsin K was found to be a single-copy gene. Northern blot analysis of RNAs from a number of mouse tissues revealed that cathepsin K mRNA is selectively expressed in osteoclast. The selective expression of cathepsin K was confirmed by anticathepsin K immunohistochemical staining. The sequence of cathepsin K expression was linked to osteoclast differentiation in vivo and in vitro by a tartrate-resistant acid phosphatase-anticathepsin K dual immunostaining technique. Cathepsin K is initially expressed at the preosteoclast stage and throughout the mature osteoclast stage. The primer extension assay indicated a major transcription start site 58 bp upstream of the initiator Met codon. The characterization of the cathepsin K gene, its promoter, and the temporal and spatial expression may provide valuable insights into its osteoclast-specific expression and the molecular mechanisms responsible for osteoclast activation.

Amino Acid Sequence↗