Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The EFII cis element is a 38-bp sequence at the 5' end of the Rous sarcoma virus long terminal repeat, extending from nucleotides -229 to -192 (with respect to the viral transcription start site), which is recognized by sequence-specific DNA-binding proteins in avian fibroblast nuclear extracts (L. Sealy and R. Chalkley, Mol. Cell. Biol. 7:787-798, 1987). We demonstrate that multiple copies of the EFII cis element strongly activate transcription of a reporter gene in vivo. We correlate the region of the EFII cis element which activates transcription in vivo with the in vitro binding site for three nuclear factors, EFIIa, EFIIb, and EFIIc. The sequence motif recognized by EFIIa, -b, and -c is also found in consensus binding sites for members of a rapidly growing family of transcription factors related to the CCAAT/enhancer-binding protein (C/EBP). EFIIa, -b, and -c are present in fibroblast and epithelial cell lines from various species but are much less abundant in differentiated rat liver and kidney cells. The EFIIa binding activity is particularly abundant in an avian B-cell lymphoma line. As judged from molecular weight analysis, cell type distribution, and sequence recognition properties, the EFII factors under study appear to differ from most of the previously described C/EBP-related factors and thus may expand the diversity of the C/EBP family.
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PMID:Characterization of nuclear proteins that bind the EFII enhancer sequence in the Rous sarcoma virus long terminal repeat. 132 70

Avian leukosis virus (ALV) induces bursal lymphoma in chickens after integration of proviral long terminal repeat (LTR) enhancer sequences next to the c-myc proto-oncogene. Labile LTR-binding proteins appear to be essential for c-myc hyperexpression, since both LTR-enhanced transcription and the activities of LTR-binding proteins are specifically decreased after inhibition of protein synthesis (A. Ruddell, M. Linial, W. Schubach, and M. Groudine, J. Virol. 62:2728-2735, 1988). This lability is restricted to hematopoietic cells from ALV-susceptible chicken strains, suggesting that the labile proteins play an important role in lymphomagenesis. The major labile activity binding to the a1 LTR region (A. Ruddell, M. Linial, and M. Groudine, Mol. Cell. Biol. 12:5660-5668, 1989) was purified from bursal lymphoma cells by conventional and oligonucleotide affinity chromatography, yielding three proteins of 35, 40, and 42 kDa. More than one of these species binds the a1 LTR region, as judged by gel shift analysis. A gene encoding an a1-binding protein (designated a1/EBP) was cloned by screening a bursal lymphoma cDNA library for fusion proteins binding the a1 LTR site. DNase I footprinting and gel shift assays indicate that the a1/EBP fusion protein binds multiple LTR CCAAT/enhancer elements in a pattern similar to that of the purified B-cell protein. DNA sequence analysis shows that this 2.2-kb cDNA encodes a 209-amino-acid open reading frame containing carboxy-terminal basic and leucine zipper motifs, indicating that a1/EBP encodes a novel member of the leucine zipper family of transcription factors.
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PMID:a1/EBP: a leucine zipper protein that binds CCAAT/enhancer elements in the avian leukosis virus long terminal repeat enhancer. 132 81

We have carried out deletion analyses of a tobacco transcription activator, TGA1a, in order to define its functional domains. TGA1a belongs to the basic-region-leucine zipper (bZIP) class of DNA-binding proteins. Like other proteins of this class, it binds to its target DNA as a dimer, and its bZIP domain is necessary and sufficient for specific DNA binding. A mutant polypeptide containing the bZIP domain alone, however, shows a lower DNA-binding affinity than the full-length TGA1a. The C-terminal portion of TGA1a, which is essential for the higher DNA-binding affinity, contains a polypeptide region that can stabilize dimeric forms of the protein. This polypeptide region is designated the dimer stabilization (DS) region. Under our in vitro conditions, TGA1a derivatives with the DS region and those without the region do not form a detectable mixed dimer. This result indicates that in addition to the leucine zipper, the DS region can serve as another determinant of the dimerization specificity of TGA1a. In fact, the DS region, when fused to another bZIP protein, C/EBP, can inhibit dimer formation between the fusion protein and native C/EBP, whereas each of these can form homodimers. Such a portable determinant of dimerization specificity has potential application in studies of DNA-binding proteins as well as in biotechnology.
Mol Cell Biol 1992 Nov
PMID:Identification of a novel dimer stabilization region in a plant bZIP transcription activator. 140 63

The process of meiosis and sporulation in the yeast Saccharomyces cerevisiae is a highly regulated developmental pathway dependent on genetic as well as nutritional signals. The HOP1 gene, which encodes a component of meiotic chromosomes, is not expressed in mitotically growing cells, but its transcription is induced shortly after yeast cells enter the meiotic pathway. Through a series of deletions and mutations in the HOP1 promoter, we located two regulatory sites that are essential for proper regulation of HOP1. One site, called URS1H, brings about repression of HOP1 in mitotic cells and functions as an activator sequence in cells undergoing meiosis. The second site, which we designated UASH, acts as an activator sequence in meiotic cells and has similarity to the binding site of the mammalian CCAAT/enhancer binding protein (C/EBP). Both sites are required for full meiotic induction of the HOP1 promoter. We conclude that in mitotic yeast cells, the URS1H site maintains the repressed state of the HOP1 promoter, masking the effect of the UASH site. Upon entry into meiosis, repression is lifted, allowing the URS1H and UASH sites to activate high-level transcription.
Mol Cell Biol 1992 Sep
PMID:Meiotic induction of the yeast HOP1 gene is controlled by positive and negative regulatory sites. 150 77

Tumor necrosis factor (TNF) has been shown to have diverse effects on a wide variety of cell types. In the mouse adipogenic TA1 cell line, TNF completely abolishes differentiation and reverts fully differentiated fat cells into fibroblasts. This block in differentiation and its reversal is due to the rapid reduction in the expression of adipose-specific genes. This study reports that the transcription factor, CCAAT/enhancer binding protein (C/EBP), previously reported to promote the differentiation of 3T3-L1 adipocytes, is expressed in TA1 cells. During their growth in culture, the levels of C/EBP, as evidenced by its cellular levels of specific mRNA, protein, and DNA binding activity, increase dramatically when cells reach confluence and proceed to differentiate. Addition of TNF to cultured preadipocytes or fully differentiated adipocytes rapidly reduces C/EBP levels and is accompanied by the decrease in expression of adipose-specific genes. C/EBP binding sites occur in several adipose-specific genes, and here it is demonstrated that its presence in a novel adipose-specific gene, Clone 47, also referred to as FSP27, may be responsible for the strong down-regulation of the expression of the Clone 47 (FSP27) promoter-linked chloramphenicol acetyl transferase gene by TNF. This study proposes that the loss of C/EBP in response to TNF treatment may in part explain the loss of the adipocyte differentiated state.
Mol Endocrinol 1992 Jul
PMID:CCAAT/enhancer binding protein expression is rapidly extinguished in TA1 adipocyte cells treated with tumor necrosis factor. 150 26

3T3-L1 preadipocytes differentiate into cells having the biochemical properties of adipocytes; tumour necrosis factor-alpha (TNF) attenuates this process. Inhibition of differentiation by this cytokine, thought to be mediated at the level of transcription, has been investigated by examining the accumulation of mRNA for six transcription factors and three diversely regulated genes during the first 24 h of the differentiation process. Upon induction of differentiation, a rapid and major accumulation of c-fos and jun-B mRNA, which returned to near basal levels within 4-6 h, was observed. In contrast, c-jun mRNA, although rapidly expressed at the induction of differentiation, remained at relatively constant levels throughout the time-course. Exposure of the cells to 5 nM TNF potentiated the accumulation of all three mRNAs but most significantly that of c-jun (12-fold), which remained elevated for at least 24 h after treatment. In control differentiating cells, krox-20 and fos-B were expressed transiently from 30 min to 2 h, while fra-1 mRNA accumulated over an extended period of 1 to 8 h. Again, TNF enhanced the accumulation of these mRNAs. Accumulation of mRNA for C/EBP, a transcription factor proposed to control the expression of genes involved in the terminally differentiated state, was attenuated after exposure of the cells to TNF. Interleukin-6 (IL-6) mRNA was expressed briefly (30 min to 2 h) and again transiently (at 8 h after induction of differentiation). TNF treatment markedly enhanced accumulation of IL-6 message. We propose that an increased cellular content of one or more transcription factors or the suppression of C/EBP may be responsible for the attenuation of differentiation induced by exposure of the cells to TNF.
J Mol Endocrinol 1992 Aug
PMID:Regulation of transcription factor mRNA accumulation during 3T3-L1 preadipocyte differentiation by tumour necrosis factor-alpha. 151 26

The tissue-specific transcriptional enhancer of the human apolipoprotein B gene contains multiple protein-binding sites spanning 718 bp. Most of the enhancer activity is found in a 443-bp fragment (+621 to +1064) that is located entirely within the second intron of the gene. Within this fragment, a 147-bp region (+806 to +952) containing a single 97-bp DNase I footprint exhibits significant enhancer activity. We now report that this footprint contains four distinct protein-binding sites that have the potential to bind nine distinct liver nuclear proteins. One of these proteins was identified as hepatocyte nuclear factor 1 (HNF-1), which binds with relatively low affinity to the 5' half of a 20-bp palindrome located at the 5' end of the large footprint. A binding site for C/EBP (or one of the related proteins that recognize similar sequences) was identified in the center of the 97-bp footprint. This binding site is coincident or overlaps with the binding sites for five other proteins, two of which appear to be distinct from the C/EBP-related family of proteins. The binding site for a nuclear factor designated protein I is located between the HNF-1 and C/EBP binding sites. Finally, the 3'-most 15 bp of the footprinted sequence contain a binding site for another nuclear protein, which we have called protein II. Mutations that abolish the binding of either HNF-1, protein II, or the C/EBP-related proteins severely reduce enhancer activity. However, deletion experiments demonstrated that neither the HNF-1-binding site alone, nor the combination of binding sites for HNF-1, protein I, and C/EBP, nor the C/EBP-binding site plus the protein II-binding site is sufficient to enhance transcription from a strong apolipoprotein B promoter. Rather, HNF-1 and C/EBP act synergistically with protein II to enhance transcription of the apolipoprotein B gene.
Mol Cell Biol 1992 Mar
PMID:Hepatocyte nuclear factor 1 and C/EBP are essential for the activity of the human apolipoprotein B gene second-intron enhancer. 154 95

The CYP2C6 gene becomes maximally transcriptionally activated in livers of postpubertal rats. We examined the role of upstream DNA and liver-specific transcription factors in regulation of this promoter by use of transient transfection of heterologous chloramphenicol acetyltransferase gene constructs and vectors containing cDNAs encoding the liver-enriched transcription factors HNF-1 alpha, C/EBP, and DBP. Only DBP was able to activate the CYP2C6 promoter in HepG2 cells. Transactivation was not observed in one mouse and two human nonhepatic origin cell lines tested. Analysis of various constructs in which CYP2C6 upstream DNA was deleted revealed that DNA between -38 to -103 was involved in DBP-mediated activation. A partially purified preparation of DBP produced a footprint between -43 and -64 bp upstream of the transcription start site. A 32P-labeled double-stranded oligonucleotide, containing sequence information corresponding to -40 to -65, bound to both partially pure DBP and extracts from livers of rats as young as 1 week and as old as 25 weeks of age, as assessed by gel mobility shift analysis. This binding was eliminated by coincubation with excess unlabeled -40/-65 double-stranded oligonucleotide and by an oligonucleotide corresponding to the D site of the rat albumin gene. A gel mobility shift-Western immunoblot analysis revealed that the -40/-65 sequence bound to DBP only in liver nuclear extracts from rats older than 3 weeks; maximal binding was observed by 7 weeks of age, and no binding was detected from 1-week-old rat liver extracts. Interestingly, the DBP-binding regions of both CYP2C6 and albumin bind to C/EBP, but this factor is capable of transactivating only the latter gene. Although the DBP-binding regions in these two genes share no obvious sequence similarities, the CYP2C6 region contains consensus palindromic half sites for DBP-related binding proteins and affinity for recombinant DBP of 17-fold greater than that of the D site of albumin. This difference in affinity is probably responsible for the markedly lower amounts of DBP required for half-maximal activation of the CYP2C6 promoter, as compared with the albumin promoter, in transactivation transfection assays. These data indicate that the CYP2C6 gene may be regulated, at least in part, by DBP, a liver transcription factor produced when rats reach puberty that may also be involved in maintenance of albumin gene transcription.
Mol Cell Biol 1992 Jun
PMID:Role of the liver-enriched transcription factor DBP in expression of the cytochrome P450 CYP2C6 gene. 158 73

Apolipoprotein B100 (apoB), the only protein of low-density lipoprotein, is produced primarily in the liver and serves as a ligand for the low-density lipoprotein receptor. Hepatic cell-specific expression of the human apoB gene is controlled by at least two cis-acting positive elements located between positions-128 and -70 (H. K. Das, T. Leff, and J.L. Breslow, J. Biol. Chem. 263:11452-11458, 1988). The distal element (-128 to -85) appears to be liver specific since it shows positive activity in HepG2 cells and negative activity in HeLa cells. The proximal element (-84 to -70) acts as a positive element in both these cell lines, and two rat liver nuclear proteins, BRF-1 and C/EBP, bind to two overlapping sites (-84 to -60 and -70 to -50, respectively). By gel mobility shift assay, we have identified a rat liver nuclear protein (BRF-2) which binds to the distal element (-128 to -85) of the apoB gene. This putative trans-acting factor has been purified to apparent homogeneity by DEAE-cellulose, heparin-agarose, and DNA-specific affinity chromatography. The purified BRF-2 has an apparent molecular mass of 120 kDa and was found to specifically recognize sequence -128 to -85; BRF-2 also produced a strong hypersensitive site at nucleotide position -95 with copper-orthophenanthroline reagent. A double-stranded oligonucleotide (-128 to -85) containing a 3-nucleotide (TTC) insertion between position -95 and -94 was found to abolish DNA binding by BRF-2. This result suggests that the region surrounding the hypersensitive site -95 is important for protein-DNA interaction. By using apoB promoter fragments containing various internal deletions as templates for gel mobility shift assay, the region between -104 and -85 was identified to be crucial for binding by BRF-2. We propose that BRF-2 may play an important role in the tissue-specific regulation of apoB gene transcription.
Mol Cell Biol 1992 Jul
PMID:Transcriptional regulation of the apolipoprotein B100 gene: purification and characterization of trans-acting factor BRF-2. 162 Jan 25

A C/EBP-like transcription factor, AGP/EBP, that binds to three distinct motifs in the 5'-flanking region of alpha 1-acid glycoprotein gene (AGP) has been identified. Here we report the cloning and properties of cDNA corresponding to mouse AGP/EBP. AGP/EBP and C/EBP share 87% amino acid sequence homology in the "leucine zipper" and its associated DNA-binding domains, while their sequences outside these domains and the sizes of their mRNAs are different. Unlike the limited expression of C/EBP in tissues and cells, AGP/EBP appears to be ubiquitously expressed in tissues like lung, spleen, kidney, heart, testis, and liver and cell lines like p388D1, 129P (hepatoma cell line of C3H/HeJ), FO (mouse myeloma), and L929. Antibody against cloned and expressed AGP/EBP which was raised in rabbits could recognize AGP/EBP from nuclear extract of a number of cells and tissues. On the basis of our findings about the structural relationship and the similarity of motif recognition, we propose that a family of C/EBP-like transcription factors exists.
Mol Cell Biol 1990 Dec
PMID:Molecular cloning of a transcription factor, AGP/EBP, that belongs to members of the C/EBP family. 170 Oct 20


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