Nuclear factor NF-kappa B can interact functionally with its cognate binding site to provide lymphoid-specific promoter function

USP15 facilitates the progression of bladder cancer by amplifying the activation of the NF-κB signaling pathway

USP15, a pivotal member of the deubiquitinase family, plays a crucial role in orchestrating numerous vital biological processes, including the regulation of NF-κB signaling pathway and deubiquitination of proto-oncogenes. In various cancers, USP15 has been validated to exhibit up-regulated expression, impacting the initiation and progression of cancer. However, its precise mechanism in bladder cancer remains elusive. Our study shed light on the significant overexpression of USP15 in bladder cancer cells compared to normal bladder cells, correlating with a poorer prognosis for bladder cancer patients. Strikingly, attenuation of USP15 expression greatly attenuated the proliferation, migration, and invasion of bladder cancer cells. Moreover, upregulation of USP15 was found to drive cancer progression through the activation of the NF-κB signaling pathway. Notably, USP15 directly deubiquitinates BRCC3, heightening its expression level, and subsequent overexpression of BRCC3 counteracted the antitumoral efficacy of USP15 downregulation. Overall, our findings elucidated the carcinogenic effects of USP15 in bladder cancer, primarily mediated by the excessive activation of the NF-κB signaling pathway, thereby promoting tumor development. These results underscore the potential of USP15 as a promising therapeutic target for bladder cancer in the future.

Porous COS@SiO2 Nanocomposites Ameliorate Severe Acute Pancreatitis and Associated Lung Injury by Regulating the Nrf2 Signaling Pathway in Mice

Severe acute pancreatitis (SAP) is associated with high rates of mortality and morbidity. Chitosan oligosaccharides (COSs) are agents with antioxidant properties. We developed porous COS@SiO₂ nanocomposites to study the protective effects and mechanisms of COS nanomedicine for the treatment of acute pancreatitis. Porous COS@SiO₂ nanocomposites released COSs slowly under pH control, enabling sustained release and maintaining the drug at a higher concentration. This study aimed to determine whether porous COS@SiO₂ nanocomposites ameliorate SAP and associated lung injury. The SAP model was established in male C57BL/6 mice by intraperitoneal injection of caerulein. The expression levels of myeloperoxidase, malondialdehyde, superoxide dismutase, nuclear factor-kappa B (NF-κB), the NOD-like receptor protein 3 (NLRP3) inflammasome, nuclear factor E2-related factor 2 (Nrf2), and inflammatory cytokines were detected, and a histological analysis of mouse pancreatic and lung tissues was performed. In the SAP groups, systemic inflammation and oxidative stress occurred, and pathological damage to the pancreas and lung was obvious. Combined with porous COS@SiO₂ nanocomposites before treatment, the systemic inflammatory response was obviously reduced, as were oxidative stress indicators in targeted tissues. It was found that Nrf2 was significantly activated in the COS@SiO₂ treatment group, and the expressions of NF-κB and the NLRP3 inflammasome were notably decreased. In addition, this protective effect was significantly weakened when Nrf2 signaling was inhibited by ML385. This demonstrated that porous COS@SiO₂ nanocomposites activate the Nrf2 signaling pathway to inhibit oxidative stress and reduce the expression of NF-κB and the NLRP3 inflammasome and the release of inflammatory factors, thus blocking the systemic inflammatory response and ultimately ameliorating SAP and associated lung injury.

NF-κB dysregulation in multiple myeloma

The nuclear factor-κB (NF-κB) transcription factor family plays critical roles in the pathophysiology of hematologic neoplasias, including multiple myeloma. The current review examines the roles that this transcription factor system plays in multiple myeloma cells and the nonmalignant accessory cells of the local microenvironment; as well as the evidence indicating that a large proportion of myeloma patients harbor genomic lesions which perturb diverse genes regulating the activity of NF-κB. This article also discusses the therapeutic targeting of the NF-κB pathway using proteasome inhibitors, a pharmacological class that has become a cornerstone in the therapeutic management of myeloma; and reviews some of the future challenges and opportunities for NF-κB-related research in myeloma.

Induction of lipocalin-2 expression in acute and chronic experimental liver injury moderated by pro-inflammatory cytokines interleukin-1β through nuclear factor-κB activation

BACKGROUND

Lipocalin-2 (LCN2) belongs to the lipocalin superfamily, sharing a barrel-shaped tertiary structure with a hydrophobic pocket and an ability to bind lipophilic molecules. LCN2 has recently emerged as an important modulator of cellular homeostasis in several organs, i.e. heart, lung and kidney, but little is known about the expression of LCN2 in acute and chronic liver injury.

AIMS

In this study, we wanted to analyse the expression and regulation of LCN2 in models of acute and chronic experimental liver injury.

MATERIALS AND METHODS

We analysed LCN2 expression in livers of rats subjected to bile duct ligation or repeated doses of carbon tetrachloride and tested the impact of various pro-inflammatory cytokines in cultured primary liver cells.

RESULTS

By using primary cultures of hepatic stellate cells and hepatocytes isolated from normal and injured rat livers, we found a significant LCN2 expression in early hepatic stellate cell cultures, a lower expression in fully transdifferentiated myofibroblasts and no expression in freshly isolated hepatocytes. However, LCN2 expression and secretion in hepatocytes increased dramatically during culturing. In addition, chronic in vivo liver injury resulting from both bile duct ligation and repeated application of carbon tetrachloride resulted in rapid and well-sustained induction of LCN2 expression. Immunohistochemistry and primary liver cell isolation identified injured hepatocytes as the main source of LCN2 production. LCN2 is strongly induced in both primary hepatocytes and immortalized hepatocellular carcinoma cell line HepG2 by the pro-inflammatory cytokine interleukin-1β via nuclear factor-κB activation, but not by the profibrotic cytokines platelet-derived growth factor and transforming growth factor-β.

CONCLUSION

LCN2 expression shows clear correlation to liver damage and resulting inflammatory responses, rather than to the degree of liver fibrosis, which in fact may imply a distinct diagnostic value as an early biomarker of liver inflammation.

Complete Sequence Assembly and Characterization of the C57BL/6 Mouse Ig Heavy Chain V Region

The mechanisms that regulate variable (V) gene selection during the development of the mouse IgH repertoire are not fully understood, due in part to the absence of the complete locus sequence. To better understand these processes, we have assembled the entire 2.5-Mb mouse IgH (Igh) V region sequence of the C57BL/6 strain from public sequences and present the first complete annotated map of the region, including V genes, pseudogenes, repeats, and nonrepetitive intergenic sequences. In so doing, we have discovered a new V gene family, VH16. We have identified clusters of conserved region-specific intergenic sequences and have verified our assembly by genic and intergenic Southern blotting. We have observed that V pseudogenes are not evenly spread throughout the V region, but rather cluster together. The largest J558 family, which spans more than half of the locus, has two strikingly different domains, which suggest points of evolutionary divergence or duplication. The 5' end contains widely spaced J558 genes interspersed with 3609 genes and is pseudogene poor. The 3' end contains closely spaced J558 genes, no 3609 genes, and is pseudogene rich. Each occupies a different branch of the phylogenetic tree. Detailed analysis of 500-bp upstream of all functional genes has revealed several conserved binding sites, general and B cell-specific, as well as key differences between families. This complete and definitive assembly of the mouse Igh V region will facilitate detailed study of promoter function and large-scale mechanisms associated with V(D)J recombination including locus contraction and antisense intergenic transcription.

Assembly and analysis of the mouse immunoglobulin kappa gene sequence

The mechanisms regulating V gene usage leading to the immunoglobulin (Ig) repertoire have been of interest for many years but are only partially defined. To gain insight into these processes, we have assembled the nucleotide sequence of the Mus musculus Igkappa locus using data recently made available from genome-wide sequencing efforts. We found the locus to be 3.21 Mb in length and mapped all known functional, pseudo- and relic V gene segments onto the sequence, along with known regulatory elements. We corrected errors in former gene assignments, positions and orientations and identified a novel Vkappa4 gene segment. This assembly allowed the establishment of a unified nomenclature for the V genes based on their relative positions similar to the nomenclature system adopted for the human Ig loci. The 5' boundary of the locus is defined by the presence of the tumor-associated calcium-signal transducer-2 gene located 19 kb upstream of Vkappa24-140, the most distal V gene. No non- Vkappa genes were found in the sequence of the locus. Detailed analysis of the sequences 0.5 kb upstream, within, and 0.5 kb downstream of each potentially functional V gene revealed interesting patterns of statistically significant clustering of transcription factor consensus binding sites, generally specific to a particular family. We found E boxes were clustered not only in promoter regions, but also nearby recombination signal sequences. Family members of Vkappa4/5 genes exhibit a conserved pattern of octamer sites in their downstream regions, as well as Ebf sites in their introns, and Lef-1 sites in their upstream regions. We discuss potential functional implications of these findings in the context of possible combinatorial mechanisms for targeting V genes for rearrangement. The assembled sequence and its analyses are available as a resource to the scientific community.

Dimerization controls the lipid raft partitioning of uPAR/CD87 and regulates its biological functions

The urokinase-type plasminogen activator receptor (uPAR/CD87) is a glycosylphosphatidylinositol-anchored membrane protein with multiple functions in extracellular proteolysis, cell adhesion, cell migration and proliferation. We now report that cell surface uPAR dimerizes and that dimeric uPAR partitions preferentially to detergent-resistant lipid rafts. Dimerization of uPAR did not require raft partitioning as the lowering of membrane cholesterol failed to reduce dimerization and as a transmembrane uPAR chimera, which does not partition to lipid rafts, also dimerized efficiently. While uPA bound to uPAR independently of its membrane localization and dimerization status, uPA-induced uPAR cleavage was strongly accelerated in lipid rafts. In contrast to uPA, the binding of Vn occurred preferentially to raft- associated dimeric uPAR and was completely blocked by cholesterol depletion.

Expression of the aldehyde dehydrogenase 2-like gene is controlled by BOB.1/OBF.1 in B lymphocytes

BOB.1/OBF.1 is a lymphocyte-restricted transcriptional coactivator. It binds to the Oct1 and Oct2 transcription factors and increases their transactivation potential. Targeted gene disruption experiments revealed that BOB.1/OBF.1 is critical at different stages of B cell development. A large number of genes expressed in B cells contain octamer motifs in their regulatory regions. However, only few genes have been described so far whose expression is dependent on BOB.1/OBF.1. To understand the molecular basis of BOB.1/OBF.1 function in B cell development, we searched for BOB.1/OBF.1 target genes by expression profiling. We have identified genes both induced and repressed by BOB.1/OBF.1. Using different genetic systems, we demonstrate regulation of a selection of these genes. Identified targets included genes encoding Ahd2-like, AKR1C13, Rbp1, Sdh, Idh2, protocadherin gamma, alpha-catenin, Ptprs, Id3, and Creg. Classification of BOB.1/OBF.1 target genes by function suggests that they affect various aspects of B cell physiology such as cellular metabolism, cell adhesion, and differentiation. To better understand the mechanism of BOB.1/OBF.1 action, we cloned the promoter of the gene encoding Ahd2-like, the gene showing the strongest regulation by BOB.1/OBF.1. This promoter indeed contains a perfect octamer motif. Furthermore, the motif was recognized by the Oct transcription factors as well as BOB.1/OBF.1 in vitro and in vivo, as shown by electromobility shift and chromatin immunoprecipitation assays. Transient transfections confirm that this promoter is activated by BOB.1/OBF.1. Our observations suggest that by regulating genes in different functional pathways, BOB.1/OBF.1 has a widespread effect on B cell development and function.

TC21 mediates transformation and cell survival via activation of phosphatidylinositol 3-kinase/Akt and NF-kappaB signaling pathway

The signaling pathways of TC21-mediated transformation and cell survival are not well-established. In this study, we have investigated the role of PI3-K/Akt signaling pathway in oncogenic-TC21-mediated transformation and cell survival. We found that oncogenic-TC21 stimulated the PI3-K activity. This was associated with the activation of Akt, a key component of PI3-K signaling pathway. We also found that TC21 interacted and formed complex with PI3-K. Mutations in the GTP-binding region of TC21, which enhanced GTP-binding potential of this protein, also stimulated its association with PI3-K, suggesting that PI3-K may preferentially interact with the GTP-bound form. Suppression of PI3-K and Akt by specific inhibitors LY294002 and Wortmannin reversed TC21-induced transformation. Likewise, inhibition of PI3-K activity by the PI3-K phosphotase PTEN reduced TC21-mediated focus formation in NIH3T3 cells. Investigation of TC21's effect on cell survival revealed that mutant-TC21 expressing cells were more resistant to etoposide- and cisplatin-induced cell death, and this was associated with the activation of anti-apoptotic protein NF-kappaB, a downstream target of Akt. Treatment of PI3-K inhibitor LY294002 significantly suppressed TC21-mediated NF-kappaB activation. In conclusion, we have identified PI3-K as an effector of TC21 and demonstrated that the PI3-K/Akt signaling pathway plays important roles in TC21-mediated transformation and cell survival.

Activation of the Ikappa B kinases by RIP via IKKgamma /NEMO-mediated oligomerization

To understand the mechanism of activation of the IkappaB kinase (IKK) complex in the tumor necrosis factor (TNF) receptor 1 pathway, we examined the possibility that oligomerization of the IKK complex triggered by ligand-induced trimerization of the TNF receptor 1 complex is responsible for activation of the IKKs. Gel filtration analysis of the IKK complex revealed that TNFalpha stimulation induces a large increase in the size of this complex, suggesting oligomerization. Substitution of the C-terminal region of IKKgamma, which interacts with RIP, with a truncated DR4 lacking its cytoplasmic death domain, produced a molecule that could induce IKK and NF-kappaB activation in cells in response to TRAIL. Enforced oligomerization of the N terminus of IKKgamma or truncated IKKalpha or IKKbeta lacking their serine-cluster domains can also induce IKK and NF-kappaB activation. These data suggest that IKKgamma functions as a signaling adaptor between the upstream regulators such as RIP and the IKKs and that oligomerization of the IKK complex by upstream regulators is a critical step in activation of this complex.

Regulation of the NF-kappaB activation pathway by isolated domains of FIP3/IKKgamma, a component of the IkappaB-alpha kinase complex

FIP3, isolated as a type 2 adenovirus E3-14.7-kDa interacting protein, is an essential component of the multimeric IkappaB-alpha kinase (IKK) complex and has been shown to interact with various components (Fas receptor-interacting protein, NF-kappaB-inducing kinase, IKKbeta) of the NF-kappaB activation pathway. FIP3 has also been shown to repress basal and tumor necrosis factor (TNF) alpha-induced NF-kappaB activity as well as to induce cell death when overexpressed. The adenovirus E3-14.7-kDa protein (E3-14.7K) is an inhibitor of TNFalpha-induced cell death. In the current study, we generated deletion mutants to map the domains of FIP3, which are responsible for its various functions. The NF-kappaB inhibitory activity and the E3-14.7K binding domains were mapped at the carboxyl half of the FIP3 protein. We also found that the carboxyl-terminal half of FIP3 blocked TNFalpha-induced IkappaB-alpha phosphorylation and subsequent degradation, which suggests that the stabilization of the cytoplasmic inhibitor of NF-kappaB underlies the FIP3 inhibition of NF-kappaB activity. The amino-terminal 119 amino acids were responsible for the FIP3-IKKbeta and FIP3-IKKalpha interaction, and the middle of the protein (amino acids 201-300) appeared to be both the FIP3 self-association domain as well as the FIP3-Fas receptor-interacting protein interaction domain. Thus, FIP3 might serve as a scaffold protein to organize the various components of the IkappaB-alpha kinase complex. Whereas the full-length protein is required for efficient cell death, the amino-terminal 200 amino acids are sufficient to cause rounding and detachment of the cells from the monolayer.

AP-1 and NF-kappaB regulation in rheumatoid arthritis and murine collagen-induced arthritis

OBJECTIVE

To determine the expression and regulation of nuclear transcription factors AP-1 and NF-kappaB in rheumatoid arthritis and in collagen-induced arthritis in mice.

METHODS

AP-1 and NF-kappaB expression and function were determined in RA, OA and normal synovial tissue by electrophoretic mobility shift assay (EMSA) and immunohistochemistry. The kinetics of transcription factor expression were then examined in collagen-induced arthritis (CIA) in mice. EMSAs were performed with the nuclear extracts obtained from paws of CIA mice from 10 to 45d after immunization to determine AP-1 and NF-kappaB binding activity. The expression of collagenase-3 (MMP13) and stromelysin (MMP3) mRNA was examined by northern blot analysis.

RESULTS

Immunohistochemistry showed that NF-kappaB expression was increased in both RA and OA synovial intimal lining. AP-1 components Jun and Fos were also present in the intimal lining and was significantly greater in RA than OA. The DNA binding activities of both AP-1 and NF-kappaB were significantly higher RA patients compared with OA. In CIA, AP-1 and NF-kappaB expression increased by day 20, which was 1-2 weeks before onset of clinical arthritis. However, collagenase and stromelysin gene expression did not increase until day 35.

CONCLUSION

The DNA binding activity of AP-1 and NF-kappaB are markedly increased in both CIA and RA. In CIA, activation of AP-1 and NF-kappaB precede both clinical arthritis and metalloproteinase gene expression. NF-kappaB expression correlated better than AP-1 with metalloproteinase expression.

RelB is a key player for both kappa B-dependent transcription and demethylation in B cells

NF-kappa B was originally identified as a B cell-specific nuclear factor binding to the intronic kappa-light-chain enhancer element. It is found constitutively in the nucleus of mature B and plasma cells. In other cell types including pre-B cells, NF-kappa B is sequestered in the cytoplasm but can be induced by a variety of stimuli. In contrast to essentially all other mature B cells and plasma cell lines, the S107 plasmacytoma cell line lacks both constitutive and inducible kappa B-binding activity. A molecular characterization of the defect in these S107 cells suggests that the primary defect lies in the signal transduction pathway leading to NF-kappa B induction. Ectopic expression of RelB after stable transfection of these cells restores constitutive nuclear kappa B-binding activity. Moreover, kappa B-dependent transcription is also restored. Finally we demonstrate, that in contrast to parental S107 cells, the stable RelB transfectants have also regained the ability to specifically demethylate a transfected immunoglobulin kappa-locus. These data suggest that RelB is critically involved in both B cell-specific transcription and demethylation directed by the intronic kappa-enhancer element.

Glutamate-dependent activation of NF-kappaB during mouse cerebellum development

NF-kappaB and activator protein 1 (AP-1) are dimeric transcription factors involved in transcriptional regulation in many cells, including neurons. We have examined their activity during mouse cerebellum development, a postnatal process starting just after birth and completed by the fourth postnatal (PN) week. The activity of these factors was analyzed by binding of nuclear extracts to a synthetic oligonucleotide representing the kappaB site of human immunodeficiency virus or the AP-1 site of the urokinase promoter. NF-kappaB activity was observed from 7 PN, was restricted to the developing cerebellum, and was not observed in the early postnatal neocortex and hippocampus. On the other hand, AP-1 activity was not found in cerebellum but was present in both neocortex and hippocampus. Moreover, a kappaB-driven transgene was found to be increasingly expressed in the cerebellum from 5 PN to 10 PN but not in the adult. The regulation of NF-kappaB activation in mouse cerebellum was analyzed by intraperitoneal injection of glutamate receptor antagonists to 9 PN mice, which abolished NF-kappaB-binding activity, suggesting an endogenous loop of glutamate receptor activation. Glutamate receptor agonists, on the other hand, induced NF-kappaB nuclear translocation in the cerebellum of 5 PN mice, which is a stage in which NF-kappaB is not yet endogenously activated. This effect was specific for NF-kappaB and not observed for AP-1. In adult mice, NF-kappaB activity was absent in the cerebellum and was not induced by intraperitoneal injection of glutamate receptor agonists. These data show that NF-kappaB is specifically activated during cerebellum development and indicate an important role of glutamate receptors in this process.

A role for nuclear NF-kappaB in B-cell-specific demethylation of the Igkappa locus

The immunoglobulin kappa gene is specifically demethylated during B-cell maturation in a process which utilizes discrete cis-acting modules such as the intronic kappa enhancer element and the matrix attachment region (MAR). While any MAR sequence is sufficient for this reaction, mutation analysis indicates that tissue specificity is mediated by kappaB binding sequences within the kappa intronic enhancer. The plasmacytoma cell line S107 lacks kappaB binding activity and fails to demethylate the kappa locus. However, B-cell specific demethylation is restored by the introduction of an active kappaB binding protein gene relB. This represents the first demonstration of a trans-acting factor involved in cell-type-specific demethylation, and suggests that the same protein-DNA recognition system used for transcription may also contribute to the earlier developmental events that bring about activation of the kappa locus.

A classical enhancer element responsive to both lipopolysaccharide and interferon-gamma augments induction of the iNOS gene in mouse macrophages

The ability of macrophages to kill some kinds of tumor cells is dependent upon the production of the free radical nitric oxide (NO) by the inducible enzyme NO synthase (iNOS; EC 1.14.13.39). Expression of the iNOS gene is induced by lipopolysaccharide (LPS) and augmented by interferon-gamma (IFN-gamma). Two regions of the iNOS promoter are known to regulate induction, a promoter proximal region I (RI) and a more distal region II (RII). Reconfiguration of RI within the iNOS regulatory region revealed its dependence upon native position and orientation for maximal activity, suggesting that it is a core promoter module, and further implicated the putative octamer element as a contributor to promoter activity. RII, however, functioned in a relatively orientation- and position-independent manner. Therefore, it had the characteristics of a classical enhancer element.

Oligoadenylate and cyclic AMP: interrelation and mutual regulation

The data obtained are in good agreement with the hypothesis that cAMP is involved in the control of 2-5A metabolism, including the mediation of the regulation of 2-5A by IFNs; 2-5A, in turn, affects the intracellular cAMP level. The general question originating from the data is that of a biochemical mechanism connecting the activation of the cAMP/2-5A system and the effect of depression of cell division. In my opinion, this universal effect is the result of the action of the known 2-5A-dependent mechanism, namely, RNase L (see review by Pestka et al. 1987), rather than by any new 2-5A-stimulating enzyme. The RNase L activated by 2-5A decreases the total level of protein synthesis and accelerates the degradation of cellular RNA, resulting in the inhibition of cell growth. It should be mentioned that such activation of RNA turnover is generally characteristic for nondividing cells, especially for cells in the resting state (Epifanova et al. 1983). Thus, the regulatory system of cAMP/2-5A is involved evidently in the antiproliferative mechanism characteristic for the resting cells, controlling the variations in the levels of RNA turnover and protein synthesis.

Distinct NF-kappa B/Rel transcription factors are responsible for tissue-specific and inducible gene activation

The NF-kappa B/Rel family is a growing class of transcriptional regulators whose members share the conserved Rel-homology domain, involved in specific DNA binding and dimerization. They interact with the regulatory elements of many different genes and are involved in the regulation of lymphoid-specific and inducible transcription. We tested whether these factors could alone activate a gene in transgenic mice. We report here that a minimal promoter containing three copies of a binding site for these proteins allows tissue-specific and inducible transgene activation. In lymphoid tissues constitutive transgene expression correlates with the presence of a constitutively active p50/RelB heterodimer. Other organs that only contain the p50 homodimer do not express the transgene. In contrast to this constitutive activity mediated by p50/RelB, the p50/p65 heterodimer (which is NF-kappa B) could confer inducible transgene activation in embryo fibroblasts. Thus two different members of the NF-kappa B/Rel family of transcriptional activators are involved in tissue-specific and inducible gene activation in transgenic mice.

Extracellular Tax1 protein stimulates tumor necrosis factor-beta and immunoglobulin kappa light chain expression in lymphoid cells

The human T-cell leukemia virus type I tax1 gene product is responsible for the increased expression of several cytokine and cellular genes that contain NF-kappa B regulatory sequences. Our laboratory has previously demonstrated that purified, extracellular Tax1 protein induced the nuclear accumulation of NF-kappa B binding activity in lymphoid cells. Since HTLV-I infection causes increased levels of lymphotoxin tumor necrosis factor-beta [TNF-beta] and immunoglobulin secretion, we have studied the interaction of NF-kappa B proteins from Tax1-stimulated cells with the TNF-beta and immunoglobulin kappa (Ig kappa) light chain genes. Tax1 induction of NF-kappa B occurred in the presence of cycloheximide, and Tax1 stimulation did not result in increased levels of NF-kappa B or c-rel RNA. These results indicate that new synthesis of NF-kappa B proteins was not required for induction of NF-kappa B-binding activity. With use of the Ig kappa NF-kappa B-binding site as a probe, two distinct NF-kappa B gel shift complexes were induced by the Tax1 protein. A slower-migrating complex, C1, was inhibited by the addition of purified I kappa B. In contrast, the faster-migrating C2 complex was not inhibited by I kappa B, but C2 was increased by detergent treatment of cytoplasmic extracts, suggesting that its binding activity was also regulated by an inhibitor. The Tax1-stimulated proteins that interacted with the NF-kappa B-binding sites in the Ig kappa and TNF-beta promoters were distinct. A 75-kDa protein preferentially associated with the Ig kappa NF-kappa B-binding site. In contrast, a 59-kDa protein associated with the TNF-beta NF-kappa B-binding site. Tax1 stimulation led to increased levels of TNF-beta and Ig kappa mRNA, as measured by reverse transcription and polymerase chain reaction analysis. These results represent the first experimental evidence that extracellular Tax1 can regulate the expression of endogenous cellular genes.

Functional similarities between human immunodeficiency virus type 1 and simian virus 40 kappa B proto-enhancers

To search for broadly active enhancer elements within the human immunodeficiency virus type 1 (HIV-1) long terminal repeat, we have used a proto-enhancer amplification assay. In this assay, the enhancer region of simian virus 40 (SV40) is replaced by heterologous regulatory sequences. Upon passage in African green monkey kidney cells. SV40 growth revertants can arise by amplification (usually duplication) of active protoenhancers within the heterologous sequences. Most of the HIV-1 U3 regulatory sequences were assayed; only amplification of one or both of the HIV-1 enhancer core kappa B motifs consistently resulted in viable SV40 virus. Examination of the cell-specific enhancer activity of the individual HIV-1 kappa B proto-enhancers showed that, like the broadly active SV40 kappa B proto-enhancer (C proto-enhancer), they are all active in noninduced cell lines of either lymphoid (H9 and Jurkat) or nonlymphoid (HeLa and CV-1) origin. Unexpectedly, one of three kappa B point mutants that exhibit little or no activity in unstimulated cells is as highly induced in stimulated Jurkat cells as are the wild-type kappa B proto-enhancers. This point mutation shows that kappa B-related proto-enhancers can display markedly different activation properties in unstimulated cells yet still activate transcription to similar levels in stimulated cells.

Differential precipitation and zinc chelate chromatography purification of biologically active HTLV-I Tax1 expressed in E. coli

A protocol which involves sequential ammonium sulfate precipitation and zinc chelate chromatography to purify the HTLV-I Tax1 protein expressed in E. coli is described. The final Tax1 product is greater than 90% pure and the yield is approximately 1 mg per liter of liquid culture. The purified Tax1 protein is biologically active in indirect in vitro DNA binding assays and cellular NF-kB induction experiments.

Tumor necrosis factor beta (TNF-beta) induces binding of the NF-kappa B transcription factor to a high-affinity kappa B element in the TNF-beta promoter

The expression of the gene encoding tumor necrosis factor beta (TNF-beta) (lymphotoxin) is induced in T cells by various extracellular stimuli. We noticed that most such stimuli also activate the NF-kappa B transcription factor. Here we demonstrate binding of purified human NF-kappa B to a sequence within positions -98 to -88 (5'-GGGGCTTCCCC-3') of the TNF-beta promoter, which is conserved between the human and mouse genes. Also the NF-kappa B from the human T-cell line Jurkat, activated upon phytohemagglutinin (PHA)/phorbol 12-myristate 13-acetate (PMA/TPA) treatment in vivo or upon deoxycholate treatment in vitro, binds with high affinity to the sequence in the TNF-beta promoter. Apart from a single mismatch, the site is identical to a cis-activating element that is involved in the inducible expression of the MHC class I gene H-2Kb and which interacts with both the inducible NF-kappa B transcription factor and the constitutive factor KBF1/H2TF1, as we demonstrate here for the site in the TNF-beta promoter. The high homology of the well characterized H-2Kb enhancer sequence with the TNF-beta site with regard to sequence and factor binding strongly supports a physiological role for NF-kappa B in the inducible expression of the TNF-beta gene. Our observation that the TNF-beta protein can rapidly induce the DNA-binding activity of NF-kappa B in Jurkat T cells and transiently increase TNF-beta mRNA levels suggests that NF-kappa B can mediate a positive autoregulation of TNF-beta synthesis.

Synergistic activation of transcription by multiple binding sites for NF-kappa B even in absence of co-operative factor binding to DNA

Regulation of eukaryotic genes is largely governed by multiple cis-acting DNA sequences recognized by specific transcription factors. The transcription factor NF-kappa B has been implicated as an important regulator of cellular and viral genes, including those of immunoglobulin kappa light chain, interleukin-2, beta-interferon, HIV-1 and cytomegalovirus. We have analyzed the effect of increasing the number of NF-kappa B sites, located directly upstream from the TATA box. Four copies of the sequence gave a more than 100-fold stimulation relative to a single copy, suggesting that NF-kappa B proteins act synergistically to bring about this dramatic increase in transcription. By DNase I footprinting we demonstrated factor binding to two adjacent NF-kappa B sites in vitro. However, we found no evidence for co-operative binding to these DNA sites. We propose that the high transcriptional activity results from another type of co-operation, based on multiple weak interactions of the NF-kappa B factors with another component of the transcription apparatus, perhaps RNA polymerase II itself.

Extinction of an immunoglobulin kappa promoter in cell hybrids is mediated by the octamer motif and correlates with suppression of Oct-2 expression

When immunoglobulin-expressing B cells are fused with fibroblasts, immunoglobulin expression is rapidly and selectively suppressed. here we demonstrate that the conserved octamer motif of a kappa light chain gene promoter plays a crucial role in mediating this "extinction" phenomenon. Replacement of this octamer site by an Sp1 or NF1 binding site is sufficient to bypass extinction. Furthermore, in early cell hybrids, immunoglobulin suppression is correlated with absence of the cell-specific transcription factor Oct-2 and its transcripts. Such hybrids cannot support transcription of a transiently introduced reporter plasmid, driven by an octamer-containing promoter, unless an expression vector encoding Oct-2 is cotransfected. Transfection of the same Oct-2 expression vector into hybrid cells is also sufficient to "reactivate" an integrated kappa promoter construct. Thus, our data further establish the role of Oct-2 for immunoglobulin transcription and show that in B cell x fibroblast hybrids, the lack of a necessary cell-specific transcription factor is involved in the extinction of immunoglobulin expression.

Effect of the AIR-1 locus on the activation of an enhancerless HLA-DQA1 promoter

Studies on the regulation of a major histocompatibility complex (MHC) class II gene, HLA-DQA1, in Ia-positive cells (Raji, a human B-lymphoma cell line) and in isogenic Ia-negative cells (RJ2.2.5, a mutant of Raji altered at the AIR-1 locus) are reported. As previously found, AIR-1 is required in its entirety for the activity of an enhancer factor, the absence of which abolishes transcription of MHC class II genes. In this paper, we show that HLA-DQA1 gene expression can be directed by an enhancerless promoter. The fact that this promoter is inactive in the RJ2.2.5 mutant suggests that the trans-acting element determined by the AIR-1 locus is not only an enhancer factor as previously described, but also acts at the MHC class II promoter level.

Transcriptional down-regulation of the rearranged C-myc expression in murine cell hybrids between a plasmacytoma and a T-cell lymphoma

Regulation of the rearranged and non-rearranged c-myc expression was studied in murine cell hybrids (SBWI and SBWII) between plasmacytoma (S194) and T-cell lymphoma (BW5147) cells. Expression of the rearranged c-myc of heterogeneous mRNA sizes (1.8 approximately 2.4 kb) was markedly down-regulated in these hybrids regardless of retention of the gene. On the other hand, expression of the non-rearranged c-myc (2.4 kb) was not significantly affected in these hybrids. Treatment of SBWI hybrid cells with cycloheximide enhanced the non-rearranged c-myc 2- to 4-fold but did not release the down-regulation of the rearranged c-myc at all, suggesting that the down-regulation of the rearranged c-myc in the hybrid cells was mainly at a transcriptional rather than a post-transcriptional level. This was supported by the results of nuclear run-on assay: the high level of run-on transcripts in S194 cells declined in SBWI hybrid cells comparable to the level in BW5147 cells. The rearranged c-myc was hemi-methylated in S194 cells and the pattern was the same in SBWI hybrid cells. Furthermore, down-regulation of the rearranged c-myc in the hybrid was also not restored by treatment with 5-azacytidine (5-AzaC), 12-O-tetradecanoylphorbol-13-acetate (TPA) or forskolin, suggesting no causative involvement of DNA methylation or protein phosphorylation in down-regulation. Higher DNase I sensitivity of the rearranged c-myc in S194 cells decreased to a similar extent to that of the non-rearranged c-myc after cell fusion with BW5147 cells. These results suggest that expression of the rearranged c-myc is down-regulated at the level of transcription in murine cell hybrids between a plasmacytoma and a T-cell lymphoma, probably by changing chromatin configuration around the gene from the open to the closed state.

Interdependence and nodule specificity of cis-acting regulatory elements in the soybean leghemoglobin lbc3 and N23 gene promoters

The qualitative and quantitative contributions of four separate cis-acting DNA elements controlling the root nodule-specific soybean leghemoglobin lbc3 gene were analyzed in transgenic Lotus corniculatus plants. Expression from internal deletions in the 5' region between positions -49 and -1956 was monitored from a CAT reporter gene. The strong positive element (SPE; -1090, -947) responsible for high-level expression was demonstrated to be an organ-specific element by deleting proximal nodule-specific control elements. Deletion of the downstream qualitative organ-specific element (OSE; -139, -102) containing the putative nodulin consensus sequences 5'AAAGAT and 5'CTCTT resulted in a low expression level. Efficient SPE enhancement is therefore dependent on the organ-specific element, which by itself does not enhance expression. This quantitative effect of the immediate upstream region carrying the consensus sequences was also found in hybrid promoter studies using the soybean nodulin N23 gene promoter, suggesting the involvement of these motifs in a regulatory mechanism for nodulin genes. Deletion of the lbc3 negative element (NE, -102, -49) linking the SPE and OSE onto the TATA box did not lead to unregulated expression. These results indicate that interaction between positive, negative and neutral qualitative elements controls lbc3 expression. Binding of the nuclear protein NAT2 at the lbc3 weak positive element (WPE; -230, -170) is probably not directly required for this mechanism.

Regulation of the immunoglobulin gene transcription

The transcription of the immunoglobulin heavy (IGH), kappa (IGK) and lambda (IGL) chain genes is coordinate and B lymphocyte specific. This expression of the immunoglobulin genes is under the control of regulatory elements: the promoters located 5' of each variable (V) gene and the enhancers located between the joining and constant genes in the IGH and IGK locus and downstream on the C kappa gene. These sequences represent sites for the binding of transcription factors. A 90-100 kDa ubiquitous proteins (NF-A1) as well as two specific B cell proteins (NF-A2, OTF-2B) bind to the octamer site of the V promoter and IGH enhancer. The NF-kB protein binds to the kB site in the intron kappa enhancer, but also to kB-like sites found in the promoter regions of other genes. This paper reviews the recent data on these factors and other transcription factors which bind to the promoters and enhancers of the immunoglobulin genes and control their expression.

Slow response variant of the B lymphoma 70Z/3 defective in LPS activation of NF-kappa B

The mouse B cell lymphoma 70Z/3 is membrane immunoglobulin M (mIgM) negative, but treatment of the cells with bacterial lipopolysaccharide (LPS) induces the expression of kappa (kappa) light chain synthesis, and the cells become mIgM+. In wild type cells, this reaction is maximal after 24 h; we have isolated a variant, 1B8, which becomes mIgM+ only after a more prolonged incubation with LPS. This delayed response results from a reduced rate of accumulation of (kappa) mRNA and protein. The transcription factor, NF-kappa B is present in the cytoplasm of both the wild type and the variant cells in its inactive form. The delay in kappa expression is correlated with the failure of NF-kappa B to be activated and translocated to the nucleus. Although NF-kappa B cannot be activated by LPS, it can be activated by treatment with phorbol ester (PMA). In contrast to the clear defect in NF-kappa B, LPS treatment of 1B8 cells causes the octamer-binding factor OTF-2 to increase normally. We conclude that the defect in 1B8 cells is in an early part of the LPS activation pathway, prior to the activation of NF-kappa B, but after the signal for OTF-2 induction. The phenotype of 1B8 demonstrates that an increase in OTF-2 alone is sufficient to cause a large increase in kappa transcription in 70Z/3 cells, but that without NF-kappa B, the response is slow to develop. In this view, NF-kappa B functions to facilitate kappa transcription and to speed its rate of increase, but is not required for the long-term response of 70Z/3 cells to LPS.

1.3E2, a variant of the B lymphoma 70Z/3, defective in activation of NF-kappa B and OTF-2

The mouse B-cell cell lymphoma 70Z/3 is a convenient model system in which to study the regulation of immunoglobulin synthesis. Three transcriptional activators of kappa (kappa) light chain synthesis have been identified for these cells: bacterial lipopolysaccharide (LPS), interferon-gamma (IFN), and interleukin-1 (IL-1). The response of the kappa gene in 70Z/3 cells to LPS is mediated by increases in two transcription factors: NF-kappa B and OTF-2. In contrast, IFN has no effect on either of these factors in 70Z/3 cells. We have isolated by immunoselection an LPS- IFN+ variant of 70Z/3 called 1.3E2. We show here that LPS treatment of these cells causes no increase in nuclear localization of either NF-kappa B or OTF-2. Although they have normal levels of cytoplasmic NF-kappa B, it cannot be activated by LPS or by phorbol 12-myristate 13-acetate (PMA) treatment of the cells. These experiments expand the genetic dissection of the molecular pathways of activation of kappa transcription in 70Z/3 cells.

The SV40 TC-II(kappa B) and the related H-2Kb enhansons exhibit different cell type specific and inducible proto-enhancer activities, but the SV40 core sequence and the AP-2 binding site have no enhanson properties

The enhancer activity of the oligomerized SV40 TC-I and TC-II sequences has been investigated in lymphoid and non-lymphoid cell lines. While the TC-I sequence had no demonstrable enhanson activity, a class C enhanson (proto-enhancer), 5'-GGAAAGTCCCC-3', overlapping the TC-II sequence and the GT-I enhanson was identified. This TC-II enhanson, which is identical to the kappa B motif from the kappa chain enhancer, was active in both lymphoid and non-lymphoid cells, which contrasts with the previously reported lymphoid cell specificity of the kappa B motif. However, its activity in non-lymphoid cells is in agreement with our previous reports describing the effect of mutations in the 'TC region' within the total SV40 enhancer in lymphoid and non-lymphoid cells. The activity of the TC-II enhanson could be moderately increased in HeLa by 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and cycloheximide treatment, indicating that the protein(s) mediating its activity may be partially repressed by the previously described inhibitor protein I kappa B. The TC-II related, H-2Kb element, 5'-TGGGGATTCCCCA-3', of the histocompatibility class I H-2Kb gene promoter is also a class C enhanson which is active in both lymphoid and non-lymphoid cells. However, in contrast to the TC-II enhanson, the H-2Kb enhanson exhibits a very low activity in HeLa cells, but can be strongly induced by TPA and/or cycloheximide treatments which suggests that its cognate factor is inactivated (repressed) by an inhibitor protein. Interestingly, cycloheximide, but not TPA treatment, could induce the activity of both the TC-II and H-2Kb enhansons in F9 embryonal carcinoma cells, suggesting that these cells lack some component(s) of the protein kinase C signal transduction pathway. We also show that oligomers of the SV40 'core' sequence, which overlaps the TC-II enhanson, had no enhanson activity in any of the cell types studied, which questions the possible role of the AP-3 protein in SV40 enhancer activity in these cell types. In addition, oligomers of the AP-2 binding sites which are present in the SV40 TC region and in the human metallothionein IIA promoter show no enhanson activity, irrespective of whether the cells are treated with TPA.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoglobulin gene transcription: molecular mechanisms

Recently, many of the proteins involved in transcriptional regulation of immunoglobulin genes have been identified, purified and their cDNAs cloned. This detailed molecular information has revealed fascinating similarities among different classes of DNA-binding proteins and has dramatically expanded the number of potential mechanisms for achieving precise tissue- and developmental stage-specific immunoglobulin transcription.

Tissue-specific transcription of the mouse alpha-fetoprotein gene promoter is dependent on HNF-1

Previous work identified four upstream cis-acting elements required for tissue-specific expression of the alpha-fetoprotein (AFP) gene: three distal enhancers and a promoter. To further define the role of the promoter in regulating AFP gene expression, segments of the region were tested for the ability to direct transcription of a reporter gene in transient expression assay. Experiments showed that the region within 250 base pairs of the start of transcription was sufficient to confer liver-specific transcription. DNase I footprinting and band shift assays indicated that the region between -130 and -100 was recognized by two factors, one of which was highly sequence specific and found only in hepatoma cells. Competition assays suggested that the liver-specific binding activity was HNF-1, previously identified by its binding to other liver-specific promoters. Mutation of the HNF-1 recognition site at -120 resulted in a significant reduction in transcription in transfection assays, suggesting a biological role for HNF-1 in the regulation of AFP expression.

The role of cis-acting promoter elements in tissue-specific albumin gene expression

The mouse albumin gene promoter has six closely spaced binding sites for nuclear proteins that are located between the TATA motif and nucleotide position -170. In vitro transcription with liver or spleen nuclear extracts of templates containing either mutated or polymerized albumin promoter elements establishes a hierarchy of the different protein binding sites for tissue-specific albumin gene transcription. The HNF-1 and C/EBP binding sites strongly activate transcription in a tissue-specific manner. The NF-Y binding site has a lower activation potential and is less specific, being equally efficient in liver and spleen nuclear extracts. The remaining elements are relatively weak activator sites.

trans-activation of viral enhancers including long terminal repeat of the human immunodeficiency virus by the hepatitis B virus X protein

Human hepatitis B virus contains an open reading frame designated X. We have investigated the trans-activating function of the hepatitis B virus X gene in regulating transcriptional control elements. In the HBV genome the major target for X trans-activation is the enhancer element. Further, the X protein stimulates several other viral promoters/enhancers including the long terminal repeats (LTR) of human retroviruses. One of the viral sequences studied in detail is the human immunodeficiency viral (HIV) LTR which is trans-activated by the X protein. Using mutational analysis of the HIV LTR, we show that the NF-kappa B sequences contained within the U3 region are involved in this stimulatory activity. Nuclear run-on analyses support the notion that X-mediated trans-activation occurs at the level of transcription.

I kappa B: a specific inhibitor of the NF-kappa B transcription factor

In cells that do not express immunoglobulin kappa light chain genes, the kappa enhancer binding protein NF-kappa B is found in cytosolic fractions and exhibits DNA binding activity only in the presence of a dissociating agent such as sodium deoxycholate. The dependence on deoxycholate is shown to result from association of NF-kappa B with a 60- to 70-kilodalton inhibitory protein (I kappa B). The fractionated inhibitor can inactivate NF-kappa B from various sources--including the nuclei of phorbol ester-treated cells--in a specific, saturable, and reversible manner. The cytoplasmic localization of the complex of NF-kappa B and I kappa B was supported by enucleation experiments. An active phorbol ester must therefore, presumably by activation of protein kinase C, cause dissociation of a cytoplasmic complex of NF-kappa B and I kappa B by modifying I kappa B. this releases active NF-kappa B which can translocate into the nucleus to activate target enhancers. The data show the existence of a phorbol ester-responsive regulatory protein that acts by controlling the DNA binding activity and subcellular localization of a transcription factor.