Showing papers on "Transcription factor published in 1991"
TL;DR: It is shown that micromolar concentrations of H2O2 can induce the expression and replication of HIV‐1 in a human T cell line and suggests that diverse agents thought to activate NF‐kappa B by distinct intracellular pathways might all act through a common mechanism involving the synthesis of ROI.
Abstract: Hydrogen peroxide and oxygen radicals are agents commonly produced during inflammatory processes. In this study, we show that micromolar concentrations of H2O2 can induce the expression and replication of HIV-1 in a human T cell line. The effect is mediated by the NF-kappa B transcription factor which is potently and rapidly activated by an H2O2 treatment of cells from its inactive cytoplasmic form. N-acetyl-L-cysteine (NAC), a well characterized antioxidant which counteracts the effects of reactive oxygen intermediates (ROI) in living cells, prevented the activation of NF-kappa B by H2O2. NAC and other thiol compounds also blocked the activation of NF-kappa B by cycloheximide, double-stranded RNA, calcium ionophore, TNF-alpha, active phorbol ester, interleukin-1, lipopolysaccharide and lectin. This suggests that diverse agents thought to activate NF-kappa B by distinct intracellular pathways might all act through a common mechanism involving the synthesis of ROI. ROI appear to serve as messengers mediating directly or indirectly the release of the inhibitory subunit I kappa B from NF-kappa B.
3,793 citations
TL;DR: The results suggest that the interaction of RB with E2F is an important event in the control of cellular proliferation and that the dissociation of the complex is part of the mechanism by which E1A inactivates RB function.
1,433 citations
TL;DR: It is suggested that the Fos/Jun and ATF/CREB families of transcription factors, which function in coupling extracellular signals to alterations in expression of specific target genes, can be grouped into a superfamily of transcription factor.
Abstract: The Fos/Jun and ATF/CREB families of transcription factors function in coupling extracellular signals to alterations in expression of specific target genes. Like many eukaryotic transcription factors, these proteins bind to DNA as dimers. Dimerization is mediated by a structure known as the "leucine-zipper" motif. Although Fos/Jun and ATF/CREB were previously thought to interact preferentially with different DNA regulatory elements (the AP-1/TRE and ATF/CRE sites, respectively), we find that members of these two families form selective cross-family heterodimers. The resulting heterodimers display distinguishable DNA binding specificities from each other and from their parental homodimers. These findings indicate that the Fos/Jun and ATF/CREB families of transcription factors are not as distinct as was previously thought. We suggest that they can be grouped into a superfamily of transcription factors.
1,265 citations
1,042 citations
TL;DR: NF-AT is formed when a signal from the antigen receptor induces a pre-existing cytoplasmic subunit to translocate to the nucleus and combine with a newly synthesized nuclear subunit of NF-AT, forming a inhibitory complex between the drug and isomerase.
Abstract: CYCLOSPORINA and FK506 inhibit T- and B-cell activation and other processes essential to an effective immune response1–3. In T lymphocytes these drugs disrupt an unknown step in the trans-mission of signals from the T-cell antigen receptor to cytokine genes that coordinate the immune response4–6. The putative intracellular receptors for FK506 and cyclosporin arecis-trans prolyl isomerases7–11. Binding of the drug inhibits isomerase activity8,10,11, but studies with other prolyl isomerase inhibitors12 and analysis of cyclosporin-resistant mutants in yeast suggest that the effects of the drug result from the formation of an inhibitory complex between the drug and isomerase13,14, and not from inhibi-tion of isomerase activity. A transcription factor, NF-AT, which is essential for early T-cell gene activation, seems to be a specific target of cyclosporin A and FK506 action because transcription directed by this protein is blocked in T cells treated with these drugs, with little or no effect on other transcription factors such as AP-1 and NF-κB (refs 15–17). Here we demonstrate that NF-AT is formed when a signal from the antigen receptor induces a pre-existing cytoplasmic subunit to translocate to the nucleus and combine with a newly synthesized nuclear subunit of NF-AT. FK506 and cyclosporin A block translocation of the cytoplasmic component without affecting synthesis of the nuclear subunit.
1,035 citations
TL;DR: The study suggests that the p50 subunit in NF‐kappa B might only serve a helper function in DNA binding whereas the p65 subunit is responsible for initiating transcription.
Abstract: The nuclear form of the NF-kappa B transcription factor binds to DNA as a heterodimer of a 50 kDa (p50) and 65 kDa (p65) polypeptide. The two polypeptides are encoded by different genes but share a long region of homology, the NRD motif, encompassing domains required for DNA binding and dimerization. In this study we have analysed the contribution of the two subunits to the strong transactivating potential of NF-kappa B. Transient expression of the p65 subunit alone resulted in a potent transactivation of a CAT reporter construct under the control of two NF-kappa B binding sites in monkey COS and mouse L cells. The strongly DNA binding p50 subunit showed only very weak, if any, induction of gene expression. Co-expression of p50 suppressed the transactivation by p65 presumably by competitive DNA binding of transcriptionally inactive p50 dimers (KBF1). Fusion of p65 sequences to DNA binding domain of the yeast GAL4 transcription factor allowed detection of the principal transactivation domain of p65 (TA1) in the C-terminal 30 amino acid sequence. TA1 is likely to adopt an amphipathic alpha-helical structure which clusters serine residues on the hydrophilic surface, a structural feature conserved between human, mouse and Xenopus p65. The unique C-terminal third of p65 contained at least one more activation domain, TA2, within a 90 amino acid sequence directly adjacent to TA1. In two mammalian cell lines, TA1 and TA2 acted separately, while in an insect cell line, the two domains were inactive after their separation. Our study suggests that the p50 subunit in NF-kappa B might only serve a helper function in DNA binding whereas the p65 subunit is responsible for initiating transcription. Homodimers of p50 seem to have the potential of down-regulating kappa B-specific gene expression.
769 citations
TL;DR: The results indicate that VP1 is a novel transcription factor possibly involved in potentiation of a seed-specific hormone response and could be functionally replaced by the activation sequence of the herpes simplex virus VP16 protein.
652 citations
TL;DR: It is demonstrated that NF-kappa B binding in vitro can be inhibited by agents that modify free sulfhydryls and modulation of the redox state of NF- kappa B could represent a post-translational control mechanism for this factor.
Abstract: NF-kappa B is a widely used regulator of inducible and tissue-specific gene control. In the cytosol, when complexed to an inhibitory molecule, I kappa B, NF-kappa B is in an inactive form and cannot bind DNA. Activation of cells with appropriate stimuli results in the dissociation of NF-kappa B from I kappa B and its translocation to the nucleus as an active binding protein. We now demonstrate that NF-kappa B binding in vitro can be inhibited by agents that modify free sulfhydryls. Binding is eliminated after treatment with N-ethylmaleimide, an alkylating agent, and diamide, an oxidizing agent. The diamide effect can be reversed by 2-mercaptoethanol. Further, 2-mercaptoethanol acts synergistically with deoxycholate plus Nonidet P-40 in converting inactive cytosolic NF-kappa B to an active DNA-binding form. It is therefore possible that modulation of the redox state of NF-kappa B could represent a post-translational control mechanism for this factor.
642 citations
TL;DR: Data suggest that LEF-1 is a regulatory participant in lymphocyte gene expression and differentiation.
Abstract: Lymphoid-specific cDNA clones were isolated that encode a nuclear protein with homology to the chromosomal nonhistone protein HMG-1 and to putative regulators of cell specialization, including the mammalian testis-determining factor SRY and fungal mating-type proteins The gene represented by the isolated cDNA clones, termed LEF-1 (lymphoid enhancer-binding factor 1), is developmentally regulated and expressed in pre-B and T lymphocytes but not in later-stage B cells or nonlymphoid tissues Both endogenous and recombinant LEF-1 were shown to bind to a functionally important site in the T-cell antigen receptor (TCR) alpha enhancer Maximal TCR alpha enhancer activity was found to parallel the cell type-specific expression pattern of LEF-1 Moreover, forced expression of recombinant LEF-1 in late stage B cells increases TCR alpha enhancer function Taken together, these data suggest that LEF-1 is a regulatory participant in lymphocyte gene expression and differentiation
601 citations
TL;DR: It is reported that a TFIID complex containing TBP is essential for transcription even at a promoter that lacks a TATA box.
Abstract: In eukaryotes, the TATA box-binding protein (TBP) is responsible for nucleating assembly of the transcription initiation machinery. Here, we report that a TFIID complex containing TBP is essential for transcription even at a promoter that lacks a TATA box. Immunopurification of TFIID reveals that the active species in reconstituting TATA-less transcription is a multisubunit complex consisting of TBP and many TBP-associated factors (TAFs).
569 citations
TL;DR: Results indicate that Sp1 has a regulatory function in addition to its general role in the transcription of housekeeping genes, suggesting that an elevated Sp1 level is associated with the differentiation process.
Abstract: The expression of the trans-acting transcription factor Sp1 in mice was defined by a combination of RNA analysis and immunohistochemical localization of the Sp1 protein. Although ubiquitously expressed, there was an unexpected difference of at least 100-fold in the amount of Sp1 message in different cell types. Sp1 protein levels showed corresponding marked differences. Substantial variations in Sp1 expression were also found in some cell types at different stages of development. Sp1 levels appeared to be highest in developing hematopoietic cells, fetal cells, and spermatids, suggesting that an elevated Sp1 level is associated with the differentiation process. These results indicate that Sp1 has a regulatory function in addition to its general role in the transcription of housekeeping genes.
TL;DR: This work reports the identification of a T cell‐specific transcription factor, TCF‐1, binding to a downstream T lymphocyte‐specific enhancer element inCD3‐epsilon expression and identifies it as a Tcell‐ specific transcription factor which might play a role in the establishment of the mature T cell phenotype.
Abstract: CD3-epsilon expression is controlled by a downstream T lymphocyte-specific enhancer element. We report the identification of a T cell-specific transcription factor, TCF-1, binding to this element. The multimerized recognition motif of TCF-1 constituted a T cell-specific enhancer. Subsequent cloning of TCF-1 identified three splice alternatives. TCF-1 contained a single DNA-binding HMG box most closely related to similar boxes in the putative mammalian sex-determining gene SRY and in the Schizosaccharomyces pombe Mc mating type gene. TCF-1 mRNA was expressed uniquely in T lymphocytes. Upon cotransfection into non-T cells, TCF-1 could transactivate through its cognate motif. These results identify TCF-1 as a T cell-specific transcription factor, which might play a role in the establishment of the mature T cell phenotype.
TL;DR: It is revealed that although AP-2 shares an underlying modular organization with other transcription factors, the regions ofAP-2 involved in transcriptional activation and DNA binding/dimerization have novel sequence characteristics.
Abstract: The mammalian transcription factor AP-2 is a sequence-specific DNA-binding protein expressed in neural crest lineages and regulated by retinoic acid. Here we report a structure/function analysis of the DNA-binding and transcription activation properties of the AP-2 protein. DNA contact studies indicate that AP-2 binds as a dimer to a palindromic recognition sequence. Furthermore, cross-linking and immunoprecipitation data illustrate that AP-2 exists as a dimer even in the absence of DNA. Examination of cDNA mutants reveals that the sequences responsible for DNA binding are located in the carboxy-terminal half of the protein. In addition, a domain mediating dimerization forms an integral component of this DNA-binding structure. Expression of AP-2 in mammalian cells demonstrates that transcriptional activation requires an additional amino-terminal domain that contains an unusually high concentration of proline residues. This proline-rich activation domain also functions when attached to the heterologous DNA-binding region of the GAL4 protein. This study reveals that although AP-2 shares an underlying modular organization with other transcription factors, the regions of AP-2 involved in transcriptional activation and DNA binding/dimerization have novel sequence characteristics.
TL;DR: The identification of a cytosolic factor that both binds to the proto-oncogene c- myc A + U-rich element and specifically destabilizes c-myc mRNA in a cell-free mRNA decay system which reconstitutes mRNA decay processes found in cells is reported.
Abstract: Transient expression of some proto-oncogenes, cytokines, and transcription factors occurs as a cellular response to growth factors, 12-O-tetradecanoylphorbol-13-acetate, antigen stimulation, or inflammation. Expression of these genes is mediated in part by the rapid turnover of their mRNAs. A + U-rich elements in the 3' untranslated regions of these mRNAs serve as one recognition signal targeting the mRNAs for rapid degradation. I report the identification of a cytosolic factor that both binds to the proto-oncogene c-myc A + U-rich element and specifically destabilizes c-myc mRNA in a cell-free mRNA decay system which reconstitutes mRNA decay processes found in cells. Proteinase K treatment of the factor abolishes its c-myc mRNA degradation activity without affecting its RNA-binding capacity. Thus, RNA substrate binding and degradation appear to be separable functions. These findings should aid in understanding how the cell selectively targets mRNAs for rapid turnover.
TL;DR: It was found that microinjection of anti-Fos and anti-Jun family antibodies efficiently blocked the entrance to the S phase of serum-stimulated or asynchronously growing cells, but the antibodies against single members of the Fos family only partially inhibited DNA synthesis.
Abstract: The expression of different members of the Jun and Fos families of transcription factors is rapidly induced following serum stimulation of quiescent fibroblasts. To determine whether these proteins are required for cell cycle progression, we microinjected affinity-purified antibodies directed against c-Fos, FosB, Fra-1, c-Jun, JunB, and JunD, and antibodies that recognize either the Fos or the Jun family of proteins, into Swiss 3T3 cells and determined their effects in cell cycle progression by monitoring DNA synthesis. We found that microinjection of anti-Fos and anti-Jun family antibodies efficiently blocked the entrance to the S phase of serum-stimulated or asynchronously growing cells. However, the antibodies against single members of the Fos family only partially inhibited DNA synthesis. In contrast, all three Jun antibodies prevented DNA synthesis more effectively than did any of the anti-Fos antibodies.
TL;DR: Regulation of WT1 expression during development of the gonads is demonstrated, WT1 is a nuclear protein, implicate WT1 in genitourinary development, and a molecular framework toward understanding genitouringinary defects observed among hereditary cases of Wilms' tumor is provided.
Abstract: The Wilms' tumor gene WT1 is a recessive oncogene that encodes a putative transcription factor implicated in nephrogenesis during kidney development. In this report we analyze expression of WT1 in the murine urogenital system. WT1 is expressed in non-germ-cell components of the testis and ovaries in both young and adult mice. In situ mRNA hybridization studies demonstrate that WT1 is expressed in the granulosa and epithelial cells of ovaries, the Sertoli cells of the testis, and in the uterine wall. In addition to the 3.1-kb WT1 transcript detected by Northern blotting of RNA from kidney, uterus, and gonads, there is an approximately 2.5-kb WT1-related mRNA species in testis. The levels of WT1 mRNA in the gonads are among the highest observed, surpassing amounts detected in the embryonic kidney. During development, these levels are differentially regulated, depending on the sexual differentiation of the gonad. Expression of WT1 mRNA in the female reproductive system does not fluctuate significantly from days 4 to 40 postpartum. In contrast, WT1 mRNA levels in the tesis increase steadily after birth, reaching their highest expression levels at day 8 postpartum and decreasing slightly as the animal matures. Expression of WT1 in the gonads is detectable as early as 12.5 days postcoitum (p.c.). As an initial step toward exploring the tissue-specific expression of WT1, DNA elements upstream of WT1 were cloned and sequenced. Three putative transcription initiation sites, utilized in testis, ovaries, and uterus, were mapped by S1 nuclease protection assays. The sequences surrounding these sites have a high G + C content, and typical upstream CCAAT and TATAA boxes are not present. These studies allowed us to identify the translation initiation site for WT1 protein synthesis. We have also used an epitope-tagging protocol to demonstrate that WT1 is a nuclear protein, consistent with its role as a transcription factor. Our results demonstrate regulation of WT1 expression during development of the gonads, implicate WT1 in genitourinary development, and provide a molecular framework toward understanding genitourinary defects observed among hereditary cases of Wilms' tumor.
TL;DR: The data presented here demonstrate that pX entered into a protein-protein complex with the cellular transcriptional factors CREB and ATF-2 and altered their DNA binding specificities, which broadened the DNA binding specificity of these regulatory proteins.
Abstract: The hepatitis B virus (HBV) X gene product trans-activates viral and cellular genes. The X protein (pX) does not bind independently to nucleic acids. The data presented here demonstrate that pX entered into a protein-protein complex with the cellular transcriptional factors CREB and ATF-2 and altered their DNA binding specificities. Although CREB and ATF-2 alone did not bind to the HBV enhancer element, a pX-CREB or pX-ATF-2 complex did bind to the HBV enhancer. Thus, the ability of pX to interact with cellular factors broadened the DNA binding specificity of these regulatory proteins and provides a mechanism for pX to participate in transcriptional regulation. This strategy of altered binding specificity may modify the repertoire of genes that can be regulated by transcriptional factors during viral infection.
TL;DR: Individual steps in the assembly of RNA polymerase II and general initiation factors into a preinitiation complex serve as points of control for activators, whose functions require additional cofactors.
Journal Article•
TL;DR: Northern blot analysis was used to investigate the kinetics of ICAM-1 mRNA synthesis upon induction with TNF-alpha and PMA, suggesting that the up-regulation of IC AM-1 by cytokines occurs at least partly at the transcriptional level.
Abstract: Human intercellular adhesion molecule-1 (ICAM-1), a specific ligand for the lymphocyte function-associated Ag-1 (LFA-1), plays an important role in leukocyte-endothelial cell interactions. It is induced by proinflammatory cytokines such as IL-1, TNF-alpha, or IFN-gamma. However, little is known concerning the intracellular regulatory mechanisms which trigger ICAM-1 up-regulation. In order to study potential regulatory elements involved in ICAM-1 induction we have cloned the human ICAM-1 gene and 5 kb of its 5'-regulatory region. The sequence of the cDNA was found to be distributed over seven exons separated by six introns, whereby each of the five extracellular Ig-like domains of ICAM-1 is encoded by its own exon. The upstream sequence harbors a number of sequence motifs implicated in the regulation and expression of eukaryotic genes, including binding sites for the transcription factors SP-1, AP-1, and NF-kB. Primer extension and S1 nuclease analysis revealed two transcription initiation sites 319 bp and 41 bp upstream of the translation start site. Consensus TATA boxes were found at the expected positions about 25 bp upstream of both start sites. Reverse transcriptase polymerase chain reaction showed differential use of the two TATA boxes in A549 and HS913T cells. Both RNA seem to code for the same for of ICAM-1 protein. For regulation studies a 1.3-kb EcoRI/SalI fragment of the 5'-flanking region was used to promote transcription of a linked luciferase reporter gene in transient-transfection assays in A549 and HS913T cells. Treatment of A549 cells with IL-1 or TNF-alpha resulted in a two- or fourfold increase in luciferase activity. Furthermore, a sixfold induction could be achieved after treatment with the phorbol ester PMA. In contrast, agents that increase intracellular cAMP levels did not induce luciferase activity. Northern blot analysis was used to investigate the kinetics of ICAM-1 mRNA synthesis upon induction with TNF-alpha and PMA. These data suggest that the up-regulation of ICAM-1 by cytokines occurs at least partly at the transcriptional level. Deletion analysis of the 1.3-kb fragment of the 5'-flanking region revealed sequences responsible for promotion and inhibition of transcription. In particular, two functionally distinct regions have been characterized: a short fragment containing an NF-kB binding site has been shown to function as an activator, followed immediately downstream by a sequence acting as a silencer element. Therefore, ICAM-1 gene expression seems to be modulated by multiple cis-acting elements.
TL;DR: The product of the RB gene is a part of E 2F-I and is involved in the regulation of E2F activity, and it is concluded that the retinoblastoma (RB) gene product copurifies with E2f-I activity.
TL;DR: The properties of four distinct activator domains of the human transcription factor Sp1 suggest that different domains of Sp1 carry out distinct functions and that the formation of multimeric complexes may direct synergism and superactivation.
Abstract: The process of transcriptional activation in eukaryotes by site-specific DNA-binding proteins is a key step in gene regulation. Here we have examined the properties of four distinct activator domains of the human transcription factor Sp1. In vivo transient cotransfection assays with Sp1 show that templates bearing multiple Sp1 sites activate transcription with a high degree of synergism. However, there is no evidence of cooperative binding of Sp1 to adjacent sites. Using deletion mutants of Sp1 we have determined that the glutamine-rich activation domains A and B and the previously uncharacterized carboxy-terminal domain D are all required for Sp1 to activate transcription synergistically. Gel-shift, DNase footprinting, and chemical cross-linking experiments reveal a strong correlation between the ability of Sp1 mutants to form homomultimeric complexes and their ability to activate transcription synergistically when bound to multiple sites. We have also examined the process of superactivation, in which a molecule of Sp1 tethered to DNA via its zinc fingers can be transcriptionally enhanced by interacting directly with fingerless Sp1 molecules. The domains involved in superactivation appear to be a subset of those necessary to achieve synergistic activation. These findings suggest that different domains of Sp1 carry out distinct functions and that the formation of multimeric complexes may direct synergism and superactivation.
TL;DR: It is reported here that this sequence is necessary and sufficient for accurate basal transcription and can restore basal level transcription from a P5 + 1 element in a HeLa extract depleted for YY1 or a Drosophila embryo extract devoid of YY 1 activity, whereas a YYl-specific antibody can block the reactivation.
Abstract: Regulation of eukaryotic messenger RNA transcription is governed by DNA sequence elements that serve as binding sites for sequence-specific transcription factors. These include upstream and downstream promoter-proximal elements, enhancers, repressors, and silencers, which modulate the rate of specific initiation by RNA polymerase II. In addition, the promoter-proximal region between -45 and +30 (relative to the start of initiation) contains two highly conserved motifs, the TATA sequence at around -30 and CA at +1. Although the TATA element-binding factor TFIID has been purified and cloned from several organisms and has provided invaluable insight into the process of transcription initiation and its regulation, little is known about factors that interact at the +1 region. We have recently shown that the adeno-associated virus type 2 P5 promoter +1 region (P5 + 1 element) binds transcription factor YY1. We report here that this sequence is necessary and sufficient for accurate basal transcription. Further, partially purified YY1 can restore basal level transcription from a P5 + 1 element in a HeLa extract depleted for YY1 or a Drosophila embryo extract devoid of YY1 activity, whereas a YY1-specific antibody can block the reactivation. Finally, using electrophoretic mobility shift assay, we have identified YY1-related factors that bind to two other transcription initiators in cellular genes.
TL;DR: Sequence analysis of oligonucleotides with high affinity for GST-RB complexes, as well as the results of competition binding studies, strongly suggest that RB can associate specifically with the transcription factor E2F or with a protein having closely related DNA-binding properties.
TL;DR: Induction of the TF gene may represent a prototypic example of gene activation in monocytic cells by assembly of transcription factor complexes, and may clarify the role of AP-1 and NF-kappa B in the regulation of other LPS-responsive genes.
Abstract: Lipopolysaccharide (LPS) activation of cells of monocytic lineage leads to rapid and transient expression of a set of inflammatory gene products, including tissue factor (TF). This transmembrane receptor is the major cellular initiator of the blood coagulation cascades, and induced expression of TF is postulated to play a role in inflammation. Functional studies using transfected THP-1 monocytic cells revealed the presence of a 56-bp LPS response element (LRE) within the TF promoter that conferred LPS responsiveness to a heterologous promoter. LPS stimulation of these cells activated proteins that bound to nucleotide sequences within the LRE resembling consensus binding sites for activator protein 1 (AP-1) and nuclear factor kappa B (NF-kappa B). Induction of the TF gene may represent a prototypic example of gene activation in monocytic cells by assembly of transcription factor complexes, and may clarify the role of AP-1 and NF-kappa B in the regulation of other LPS-responsive genes.
TL;DR: The results strongly suggest that the trans-activation function of TEF-1 is mediated by a highly limiting, possible cell-specific, titratable transcriptional intermediary factor(s).
TL;DR: DNase I cleavage-inhibition patterns (footprinting) of the C/EBP gene promoter by nuclear factors from differentiated and undifferentiated 3T3-L1 cells identified two sites of differential factor binding.
Abstract: Differentiation of 3T3-L1 preadipocytes into adipocytes is accompanied by increased expression of the nuclear protein C/EBP (CCAAT/enhancer binding protein) and by transcriptional activation of a group of adipose-specific genes. We report here the isolation of the murine C/EBP gene and the characterization of its promoter. Consistent with its proposed role in coordinating transcription during preadipocyte differentiation, an increase in the rate of transcription of the C/EBP gene precedes that of several adipose-specific genes whose promoters are transactivated by C/EBP. DNase I cleavage-inhibition patterns (footprinting) of the C/EBP gene promoter by nuclear factors from differentiated and undifferentiated 3T3-L1 cells identified two sites of differential factor binding. One site in the C/EBP gene promoter between nucleotides -252 and -239 binds a nuclear factor(s) present in preadipocytes that is lost or modified upon differentiation. Another site, between nucleotides -203 and -176, exhibits different but overlapping footprints by nuclear factors present in differentiated and undifferentiated cells. Gel retardation analysis with oligonucleotides corresponding to these sites revealed protein-oligonucleotide complexes containing these differentially expressed nuclear factors. The factor present in differentiated cells that binds at this site was identified as C/EBP (possibly in heterodimeric form with a homologous leucine-zipper protein), suggesting that C/EBP may regulate expression of its own gene.
TL;DR: The lyt -10 gene defines a new subfamily (rel/poly-G/ankyrin) of NF-κB-rel transcription factors with potential for oncogenic activation in human cancer.
TL;DR: There is a striking difference in the levels of mHSF1 mRNA in different tissues of the mouse, and the ability of these two mouse heat shock factors to bind to the heat shock element (HSE) is regulated by heat.
Abstract: We have cloned two distinct mouse heat shock transcription factor genes, mHSF1 and mHSF2. The mHSF1 and mHSF2 open reading frames are similar in size, containing 503 and 517 amino acids, respectively. Although mHSF1 and mHSF2 are quite divergent overall (only 38% identity), they display extensive homology in the DNA-binding and oligomerization domains that are conserved in the heat shock factors of Saccharomyces cerevisiae, Kluyveromyces lactis, Drosophila, tomato, and human. The ability of these two mouse heat shock factors to bind to the heat shock element (HSE) is regulated by heat. mHSF1 is expressed in an in vitro translation system in an inactive form that is activated to DNA binding by incubation at temperatures greater than 41 degrees C, the same temperatures that activate heat shock factor DNA binding and the stress response in mouse cells in vivo. mHSF2, on the other hand, is expressed in a form that binds DNA constitutively but loses DNA binding by incubation at greater than 41 degrees C. Both mHSF1 and mHSF2 are encoded by single-copy genes, and neither is transcriptionally regulated by heat shock. However, there is a striking difference in the levels of mHSF1 mRNA in different tissues of the mouse.
TL;DR: P49 acts in synergy with p65 to stimulate the human immunodeficiency virus (HIV) enhancer in transiently transfected Jurkat cells, suggesting p49/plOO NF-κB could be important in the regulation of HIV and other κB-containing genes.
Abstract: The transcription factor NF-kappa B is a protein complex which comprises a DNA-binding subunit and an associated transactivation protein (of relative molecular masses 50,000 (50K) and 65K, respectively). Both the 50K and 65K subunits have similarity with the rel oncogene and the Drosophila maternal effect gene dorsal. The 50K DNA-binding subunit was previously thought to be a unique protein, derived from the 105K gene product (p105). We now report the isolation of a complementary DNA that encodes an alternative DNA-binding subunit of NF-kappa B. It is more similar to p105 NF-kappa B than other family members and defines a new subset of rel-related genes. It is synthesized as approximately 100K protein (p100) that is expressed in different cell types, contains cell cycle motifs and, like p105, must be processed to generate a 50K form. A 49K product (p49) can be generated independently from an alternatively spliced transcript; it has specific kappa B DNA-binding activity and can form heterodimers with other rel proteins. In contrast to the approximately 50K protein derived from p105, p49 acts in synergy with p65 to stimulate the human immunodeficiency virus (HIV) enhancer in transiently transfected Jurkat cells. p49/p100 NF-kappa B could therefore be important in the regulation of HIV and other kappa B-containing genes.